From 0ebb334788c564c8fd7108a589ebbeed85ad9056 Mon Sep 17 00:00:00 2001
From: Ryan Cebulko <ryan@cebulko.com>
Date: Tue, 2 Mar 2021 13:19:58 -0500
Subject: [PATCH 01/15] Standalone assert stringify elements, add
 i-amphtml-error

---
 src/core/assert.js | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/src/core/assert.js b/src/core/assert.js
index 8b84f9f8fe2d..a464cded47cc 100644
--- a/src/core/assert.js
+++ b/src/core/assert.js
@@ -27,6 +27,19 @@
  */
 export const USER_ERROR_SENTINEL = '\u200B\u200B\u200B';
 
+/**
+ * Converts an element to a readable string; all other types are unchanged.
+ * @param {*} val
+ * @return {*}
+ */
+function elementStringOrPassThru(val) {
+  // Do check equivalent to `val instanceof Element` without cross-window bug
+  if (val?.nodeType == 1) {
+    return val.tagName.toLowerCase() + (val.id ? `#${val.id}` : '');
+  }
+  return val;
+}
+
 /**
  * User error class for use in Preact. Use of sentinel string instead of a
  * boolean to check user errors because errors could be rethrown by some native
@@ -92,12 +105,15 @@ function assertion(errorCls, shouldBeTruthy, opt_message, var_args) {
       firstElement = subValue;
     }
 
-    return subValue;
+    return elementStringOrPassThru(subValue);
   });
 
   const error = new errorCls(message);
   error.messageArray = messageArray;
-  error.associatedElement = firstElement;
+  if (firstElement) {
+    error.associatedElement = firstElement;
+    firstElement.classList.add('i-amphtml-error');
+  }
   throw error;
 }
 

From 3370c7aa9db4ea6afd021fd74b04f25e671fc5b8 Mon Sep 17 00:00:00 2001
From: Ryan Cebulko <ryan@cebulko.com>
Date: Tue, 2 Mar 2021 13:30:17 -0500
Subject: [PATCH 02/15] Move helpers to separate module

---
 src/core/assert.js                | 29 ++++------------------
 src/core/error-message-helpers.js | 40 +++++++++++++++++++++++++++++++
 src/log.js                        | 17 ++++---------
 3 files changed, 49 insertions(+), 37 deletions(-)
 create mode 100644 src/core/error-message-helpers.js

diff --git a/src/core/assert.js b/src/core/assert.js
index a464cded47cc..c7c6b4997ae9 100644
--- a/src/core/assert.js
+++ b/src/core/assert.js
@@ -14,31 +14,12 @@
  * limitations under the License.
  */
 
-/** @fileoverview Dependency-free assertion helpers for use in Preact. */
-
-/**
- * Triple zero width space.
- *
- * This is added to user error messages, so that we can later identify
- * them, when the only thing that we have is the message. This is the
- * case in many browsers when the global exception handler is invoked.
- *
- * @const {string}
- */
-export const USER_ERROR_SENTINEL = '\u200B\u200B\u200B';
+import {
+  USER_ERROR_SENTINEL,
+  elementStringOrPassThru,
+} from './error-message-helpers';
 
-/**
- * Converts an element to a readable string; all other types are unchanged.
- * @param {*} val
- * @return {*}
- */
-function elementStringOrPassThru(val) {
-  // Do check equivalent to `val instanceof Element` without cross-window bug
-  if (val?.nodeType == 1) {
-    return val.tagName.toLowerCase() + (val.id ? `#${val.id}` : '');
-  }
-  return val;
-}
+/** @fileoverview Dependency-free assertion helpers for use in Preact. */
 
 /**
  * User error class for use in Preact. Use of sentinel string instead of a
diff --git a/src/core/error-message-helpers.js b/src/core/error-message-helpers.js
new file mode 100644
index 000000000000..3e0fbc8b518b
--- /dev/null
+++ b/src/core/error-message-helpers.js
@@ -0,0 +1,40 @@
+/**
+ * Copyright 2021 The AMP HTML Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS-IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * Triple zero width space.
+ *
+ * This is added to user error messages, so that we can later identify
+ * them, when the only thing that we have is the message. This is the
+ * case in many browsers when the global exception handler is invoked.
+ *
+ * @const {string}
+ */
+export const USER_ERROR_SENTINEL = '\u200B\u200B\u200B';
+
+/**
+ * Converts an element to a readable string; all other types are unchanged.
+ * TODO(rcebulko): Unify with log.js
+ * @param {*} val
+ * @return {*}
+ */
+export function elementStringOrPassThru(val) {
+  // Do check equivalent to `val instanceof Element` without cross-window bug
+  if (val?.nodeType == 1) {
+    return val.tagName.toLowerCase() + (val.id ? `#${val.id}` : '');
+  }
+  return val;
+}
diff --git a/src/log.js b/src/log.js
index 5f41f77936e6..ccc888728329 100644
--- a/src/log.js
+++ b/src/log.js
@@ -14,7 +14,10 @@
  * limitations under the License.
  */
 
-import {USER_ERROR_SENTINEL} from './core/assert';
+import {
+  USER_ERROR_SENTINEL,
+  elementStringOrPassthru,
+} from './core/error-message-helpers';
 import {getMode} from './mode';
 import {internalRuntimeVersion} from './internal-version';
 import {isArray, isEnumValue} from './types';
@@ -634,18 +637,6 @@ export class Log {
 const stringOrElementString = (val) =>
   /** @type {string} */ (elementStringOrPassthru(val));
 
-/**
- * @param {*} val
- * @return {*}
- */
-function elementStringOrPassthru(val) {
-  // Do check equivalent to `val instanceof Element` without cross-window bug
-  if (val && val.nodeType == 1) {
-    return val.tagName.toLowerCase() + (val.id ? '#' + val.id : '');
-  }
-  return val;
-}
-
 /**
  * @param {!Array} array
  * @param {*} val

From 389958529092240f3e7cbeb87dfc291dd57b6dee Mon Sep 17 00:00:00 2001
From: Ryan Cebulko <ryan@cebulko.com>
Date: Tue, 2 Mar 2021 13:46:13 -0500
Subject: [PATCH 03/15] Fix typo

---
 src/log.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/log.js b/src/log.js
index ccc888728329..623a9de6c3fb 100644
--- a/src/log.js
+++ b/src/log.js
@@ -16,7 +16,7 @@
 
 import {
   USER_ERROR_SENTINEL,
-  elementStringOrPassthru,
+  elementStringOrPassThru,
 } from './core/error-message-helpers';
 import {getMode} from './mode';
 import {internalRuntimeVersion} from './internal-version';

From 8212fd8237c5ab2ec0a18f8d3011a74890b5b7ff Mon Sep 17 00:00:00 2001
From: Ryan Cebulko <ryan@cebulko.com>
Date: Tue, 2 Mar 2021 13:48:42 -0500
Subject: [PATCH 04/15] Fix typo: The Sequal

---
 src/log.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/log.js b/src/log.js
index 623a9de6c3fb..b2a9d50f8b60 100644
--- a/src/log.js
+++ b/src/log.js
@@ -125,7 +125,7 @@ const externalMessagesSimpleTableUrl = () =>
  * @return {string}
  */
 const messageArgToEncodedComponent = (arg) =>
-  encodeURIComponent(String(elementStringOrPassthru(arg)));
+  encodeURIComponent(String(elementStringOrPassThru(arg)));
 
 /**
  * Logging class. Use of sentinel string instead of a boolean to check user/dev

From d46553d5290b7884d41a11d5c47e56367fcad2b7 Mon Sep 17 00:00:00 2001
From: Ryan Cebulko <ryan@cebulko.com>
Date: Tue, 2 Mar 2021 15:52:02 -0500
Subject: [PATCH 05/15] Fix typo

---
 src/log.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/log.js b/src/log.js
index b2a9d50f8b60..c9952934342a 100644
--- a/src/log.js
+++ b/src/log.js
@@ -635,7 +635,7 @@ export class Log {
  * @return {string}
  */
 const stringOrElementString = (val) =>
-  /** @type {string} */ (elementStringOrPassthru(val));
+  /** @type {string} */ (elementStringOrPassThru(val));
 
 /**
  * @param {!Array} array

From b3cf8f6e616eb6d475e4f04e80560bfc55a7c971 Mon Sep 17 00:00:00 2001
From: Ryan Cebulko <ryan@cebulko.com>
Date: Tue, 2 Mar 2021 16:33:13 -0500
Subject: [PATCH 06/15] Fix import

---
 test/unit/test-assert.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/unit/test-assert.js b/test/unit/test-assert.js
index 58355f840f65..bd1321fe035a 100644
--- a/test/unit/test-assert.js
+++ b/test/unit/test-assert.js
@@ -14,8 +14,8 @@
  * limitations under the License.
  */
 
+import {USER_ERROR_SENTINEL} from '../../src/core/error-message-helpers';
 import {
-  USER_ERROR_SENTINEL,
   pureDevAssert as devAssert,
   pureUserAssert as userAssert,
 } from '../../src/core/assert';

From 934eeb42894e84cc72c34c061e659c7638fb45bd Mon Sep 17 00:00:00 2001
From: Ryan Cebulko <ryan@cebulko.com>
Date: Mon, 22 Feb 2021 12:04:50 -0500
Subject: [PATCH 07/15] Update all single imports of devAssert to use
 standalone helper

---
 ads/vendors/csa.js                                            | 2 +-
 extensions/amp-a4a/0.1/amp-ad-template-helper.js              | 2 +-
 extensions/amp-a4a/0.1/friendly-frame-renderer.js             | 2 +-
 extensions/amp-a4a/0.1/template-renderer.js                   | 2 +-
 extensions/amp-access-scroll/0.1/scroll-component.js          | 2 +-
 extensions/amp-ad-custom/0.1/amp-ad-custom.js                 | 2 +-
 .../amp-ad-network-adsense-impl/0.1/adsense-shared-state.js   | 2 +-
 .../0.1/test/test-doubleclick-sra.js                          | 2 +-
 extensions/amp-ad/0.1/amp-ad-ui.js                            | 2 +-
 extensions/amp-analytics/0.1/scroll-manager.js                | 2 +-
 extensions/amp-analytics/0.1/visibility-model.js              | 2 +-
 .../amp-animation/0.1/runners/native-web-animation-runner.js  | 2 +-
 extensions/amp-fx-collection/0.1/providers/fx-provider.js     | 2 +-
 .../amp-inline-gallery/0.1/amp-inline-gallery-pagination.js   | 2 +-
 extensions/amp-lightbox-gallery/0.1/lightbox-controls.js      | 2 +-
 extensions/amp-next-page/1.0/page.js                          | 2 +-
 extensions/amp-next-page/1.0/visibility-observer.js           | 2 +-
 .../amp-story-auto-analytics/0.1/amp-story-auto-analytics.js  | 2 +-
 extensions/amp-story/1.0/pagination-buttons.js                | 4 ++--
 extensions/amp-story/1.0/simple-template.js                   | 2 +-
 extensions/amp-truncate-text/0.1/binary-search.js             | 2 +-
 extensions/amp-viewer-integration/0.1/findtext.js             | 2 +-
 src/action-constants.js                                       | 2 +-
 src/context/component-hooks.js                                | 2 +-
 src/context/node.js                                           | 2 +-
 src/context/prop.js                                           | 2 +-
 src/css.js                                                    | 2 +-
 src/extension-analytics.js                                    | 2 +-
 src/finite-state-machine.js                                   | 2 +-
 src/gesture.js                                                | 2 +-
 src/modal.js                                                  | 2 +-
 src/preact/base-element.js                                    | 2 +-
 src/render-delaying-services.js                               | 2 +-
 src/service/core-services.js                                  | 2 +-
 src/service/hidden-observer-impl.js                           | 2 +-
 src/service/owners-impl.js                                    | 2 +-
 src/service/position-observer/position-observer-worker.js     | 2 +-
 src/service/task-queue.js                                     | 2 +-
 src/service/variable-source.js                                | 2 +-
 src/static-template.js                                        | 2 +-
 src/utils/bytes.js                                            | 2 +-
 src/utils/detached-dom-stream.js                              | 2 +-
 src/utils/math.js                                             | 2 +-
 src/viewport-observer.js                                      | 2 +-
 44 files changed, 45 insertions(+), 45 deletions(-)

diff --git a/ads/vendors/csa.js b/ads/vendors/csa.js
index 72efde41ad30..d91bf42b0f70 100644
--- a/ads/vendors/csa.js
+++ b/ads/vendors/csa.js
@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-import {devAssert} from '../../src/log';
+import {pureDevAssert as devAssert} from '../../src/pure-assert';
 import {getStyle, setStyle, setStyles} from '../../src/style';
 import {loadScript, validateData} from '../../3p/3p';
 import {tryParseJson} from '../../src/json.js';
diff --git a/extensions/amp-a4a/0.1/amp-ad-template-helper.js b/extensions/amp-a4a/0.1/amp-ad-template-helper.js
index 0998f70f455f..4e9fe863d01c 100644
--- a/extensions/amp-a4a/0.1/amp-ad-template-helper.js
+++ b/extensions/amp-a4a/0.1/amp-ad-template-helper.js
@@ -17,7 +17,7 @@
 import {LruCache} from '../../../src/utils/lru-cache';
 import {Services} from '../../../src/services';
 import {createElementWithAttributes} from '../../../src/dom';
-import {devAssert} from '../../../src/log';
+import {pureDevAssert as devAssert} from '../../../src/pure-assert';
 import {dict} from '../../../src/utils/object';
 import {getMode} from '../../../src/mode';
 import {isArray} from '../../../src/types';
diff --git a/extensions/amp-a4a/0.1/friendly-frame-renderer.js b/extensions/amp-a4a/0.1/friendly-frame-renderer.js
index c6fc637b93c9..1dfdcadc6fb5 100644
--- a/extensions/amp-a4a/0.1/friendly-frame-renderer.js
+++ b/extensions/amp-a4a/0.1/friendly-frame-renderer.js
@@ -15,7 +15,7 @@
  */
 
 import {Renderer} from './amp-ad-type-defs';
-import {devAssert} from '../../../src/log';
+import {pureDevAssert as devAssert} from '../../../src/pure-assert';
 import {renderCreativeIntoFriendlyFrame} from './friendly-frame-util';
 
 /**
diff --git a/extensions/amp-a4a/0.1/template-renderer.js b/extensions/amp-a4a/0.1/template-renderer.js
index ad3ef6a25a07..27a09d692b14 100644
--- a/extensions/amp-a4a/0.1/template-renderer.js
+++ b/extensions/amp-a4a/0.1/template-renderer.js
@@ -15,7 +15,7 @@
  */
 
 import {Renderer} from './amp-ad-type-defs';
-import {devAssert} from '../../../src/log';
+import {devAssert} from '../../../src/assert';
 import {getAmpAdTemplateHelper} from './template-validator';
 import {renderCreativeIntoFriendlyFrame} from './friendly-frame-util';
 
diff --git a/extensions/amp-access-scroll/0.1/scroll-component.js b/extensions/amp-access-scroll/0.1/scroll-component.js
index 9d8e18c6647c..dbbe6e8b4695 100644
--- a/extensions/amp-access-scroll/0.1/scroll-component.js
+++ b/extensions/amp-access-scroll/0.1/scroll-component.js
@@ -17,7 +17,7 @@
 import {Services} from '../../../src/services';
 import {assertDoesNotContainDisplay, px, setStyles} from '../../../src/style';
 import {createElementWithAttributes} from '../../../src/dom';
-import {devAssert} from '../../../src/log';
+import {pureDevAssert as devAssert} from '../../../src/pure-assert';
 import {hasOwn} from '../../../src/utils/object';
 
 /** @abstract */
diff --git a/extensions/amp-ad-custom/0.1/amp-ad-custom.js b/extensions/amp-ad-custom/0.1/amp-ad-custom.js
index 88710441b7e0..09a76ce9fcf3 100644
--- a/extensions/amp-ad-custom/0.1/amp-ad-custom.js
+++ b/extensions/amp-ad-custom/0.1/amp-ad-custom.js
@@ -24,7 +24,7 @@ import {Services} from '../../../src/services';
 import {TemplateRenderer} from '../../amp-a4a/0.1/template-renderer';
 import {TemplateValidator} from '../../amp-a4a/0.1/template-validator';
 import {addParamToUrl} from '../../../src/url';
-import {devAssert} from '../../../src/log';
+import {pureDevAssert as devAssert} from '../../../src/pure-assert';
 
 // These have no side-effects, and so may be reused between all instances.
 const validator = new TemplateValidator();
diff --git a/extensions/amp-ad-network-adsense-impl/0.1/adsense-shared-state.js b/extensions/amp-ad-network-adsense-impl/0.1/adsense-shared-state.js
index 3e7d8b27ad1c..c83a14afe657 100644
--- a/extensions/amp-ad-network-adsense-impl/0.1/adsense-shared-state.js
+++ b/extensions/amp-ad-network-adsense-impl/0.1/adsense-shared-state.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {devAssert} from '../../../src/log';
+import {pureDevAssert as devAssert} from '../../../src/pure-assert';
 
 /**
  * Maintains state in between different AdSense slots on the same page. This
diff --git a/extensions/amp-ad-network-doubleclick-impl/0.1/test/test-doubleclick-sra.js b/extensions/amp-ad-network-doubleclick-impl/0.1/test/test-doubleclick-sra.js
index aea547fd2fb8..fa50a90c1558 100644
--- a/extensions/amp-ad-network-doubleclick-impl/0.1/test/test-doubleclick-sra.js
+++ b/extensions/amp-ad-network-doubleclick-impl/0.1/test/test-doubleclick-sra.js
@@ -50,7 +50,7 @@ import {
 } from '../sra-utils';
 import {Xhr} from '../../../../src/service/xhr-impl';
 import {createElementWithAttributes} from '../../../../src/dom';
-import {devAssert} from '../../../../src/log';
+import {pureDevAssert as devAssert} from '../../../../src/pure-assert';
 import {layoutRectLtwh} from '../../../../src/layout-rect';
 import {utf8Decode, utf8Encode} from '../../../../src/utils/bytes';
 
diff --git a/extensions/amp-ad/0.1/amp-ad-ui.js b/extensions/amp-ad/0.1/amp-ad-ui.js
index d74ea92d7f1a..9626e0eb7246 100644
--- a/extensions/amp-ad/0.1/amp-ad-ui.js
+++ b/extensions/amp-ad/0.1/amp-ad-ui.js
@@ -24,7 +24,7 @@ import {
   createElementWithAttributes,
   removeElement,
 } from '../../../src/dom';
-import {devAssert} from '../../../src/log';
+import {pureDevAssert as devAssert} from '../../../src/pure-assert';
 import {dict} from '../../../src/utils/object';
 import {getExperimentBranch} from '../../../src/experiments';
 
diff --git a/extensions/amp-analytics/0.1/scroll-manager.js b/extensions/amp-analytics/0.1/scroll-manager.js
index 714480a440d7..32184519736c 100644
--- a/extensions/amp-analytics/0.1/scroll-manager.js
+++ b/extensions/amp-analytics/0.1/scroll-manager.js
@@ -16,7 +16,7 @@
 
 import {Observable} from '../../../src/observable';
 import {Services} from '../../../src/services';
-import {devAssert} from '../../../src/log';
+import {pureDevAssert as devAssert} from '../../../src/pure-assert';
 
 /**
  * @typedef {{
diff --git a/extensions/amp-analytics/0.1/visibility-model.js b/extensions/amp-analytics/0.1/visibility-model.js
index 1b4b054ae05b..825b3c2b916e 100644
--- a/extensions/amp-analytics/0.1/visibility-model.js
+++ b/extensions/amp-analytics/0.1/visibility-model.js
@@ -16,7 +16,7 @@
 
 import {Deferred} from '../../../src/utils/promise';
 import {Observable} from '../../../src/observable';
-import {devAssert} from '../../../src/log';
+import {pureDevAssert as devAssert} from '../../../src/pure-assert';
 import {dict} from '../../../src/utils/object';
 
 /**
diff --git a/extensions/amp-animation/0.1/runners/native-web-animation-runner.js b/extensions/amp-animation/0.1/runners/native-web-animation-runner.js
index 8b023a63e1ac..5ff363495599 100644
--- a/extensions/amp-animation/0.1/runners/native-web-animation-runner.js
+++ b/extensions/amp-animation/0.1/runners/native-web-animation-runner.js
@@ -29,7 +29,7 @@ import {
   WebSwitchAnimationDef,
 } from '../web-animation-types';
 import {assertDoesNotContainDisplay, setStyles} from '../../../../src/style';
-import {devAssert} from '../../../../src/log';
+import {pureDevAssert as devAssert} from '../../../../src/pure-assert';
 import {getTotalDuration} from './utils';
 
 /**
diff --git a/extensions/amp-fx-collection/0.1/providers/fx-provider.js b/extensions/amp-fx-collection/0.1/providers/fx-provider.js
index 234b57961c9f..da350ffb6699 100644
--- a/extensions/amp-fx-collection/0.1/providers/fx-provider.js
+++ b/extensions/amp-fx-collection/0.1/providers/fx-provider.js
@@ -41,7 +41,7 @@ import {
   installStyles,
   resolvePercentageToNumber,
 } from './amp-fx-presets-utils';
-import {devAssert} from '../../../../src/log';
+import {pureDevAssert as devAssert} from '../../../../src/pure-assert';
 import {
   getServiceForDoc,
   registerServiceBuilderForDoc,
diff --git a/extensions/amp-inline-gallery/0.1/amp-inline-gallery-pagination.js b/extensions/amp-inline-gallery/0.1/amp-inline-gallery-pagination.js
index 9dabc3790416..a292406864b9 100644
--- a/extensions/amp-inline-gallery/0.1/amp-inline-gallery-pagination.js
+++ b/extensions/amp-inline-gallery/0.1/amp-inline-gallery-pagination.js
@@ -17,7 +17,7 @@
 import {InlineGalleryEvents} from './inline-gallery-events';
 import {Layout} from '../../../src/layout';
 import {createCustomEvent} from '../../../src/event-helper';
-import {devAssert} from '../../../src/log';
+import {pureDevAssert as devAssert} from '../../../src/pure-assert';
 import {dict} from '../../../src/utils/object';
 import {htmlFor} from '../../../src/static-template';
 import {scopedQuerySelectorAll} from '../../../src/dom';
diff --git a/extensions/amp-lightbox-gallery/0.1/lightbox-controls.js b/extensions/amp-lightbox-gallery/0.1/lightbox-controls.js
index 18251b1f8550..68e203c6c030 100644
--- a/extensions/amp-lightbox-gallery/0.1/lightbox-controls.js
+++ b/extensions/amp-lightbox-gallery/0.1/lightbox-controls.js
@@ -16,7 +16,7 @@
 
 import {Services} from '../../../src/services';
 import {createCustomEvent} from '../../../src/event-helper';
-import {devAssert} from '../../../src/log';
+import {pureDevAssert as devAssert} from '../../../src/pure-assert';
 import {dict} from '../../../src/utils/object';
 import {htmlFor} from '../../../src/static-template';
 import {toArray} from '../../../src/types';
diff --git a/extensions/amp-next-page/1.0/page.js b/extensions/amp-next-page/1.0/page.js
index e552d811aa68..53f70fc768a3 100644
--- a/extensions/amp-next-page/1.0/page.js
+++ b/extensions/amp-next-page/1.0/page.js
@@ -16,7 +16,7 @@
 
 import {ViewportRelativePos} from './visibility-observer';
 import {VisibilityState} from '../../../src/visibility-state';
-import {devAssert} from '../../../src/log';
+import {pureDevAssert as devAssert} from '../../../src/pure-assert';
 
 /** @enum {number} */
 export const PageState = {
diff --git a/extensions/amp-next-page/1.0/visibility-observer.js b/extensions/amp-next-page/1.0/visibility-observer.js
index 3b2176957b8d..82679fa3205c 100644
--- a/extensions/amp-next-page/1.0/visibility-observer.js
+++ b/extensions/amp-next-page/1.0/visibility-observer.js
@@ -24,7 +24,7 @@ import {
 } from '../../../src/service/position-observer/position-observer-impl';
 import {RelativePositions} from '../../../src/layout-rect';
 import {Services} from '../../../src/services';
-import {devAssert} from '../../../src/log';
+import {pureDevAssert as devAssert} from '../../../src/pure-assert';
 import {throttle} from '../../../src/utils/rate-limit';
 
 /** @enum {number} */
diff --git a/extensions/amp-story-auto-analytics/0.1/amp-story-auto-analytics.js b/extensions/amp-story-auto-analytics/0.1/amp-story-auto-analytics.js
index 1321059f2af6..56954c2b35da 100644
--- a/extensions/amp-story-auto-analytics/0.1/amp-story-auto-analytics.js
+++ b/extensions/amp-story-auto-analytics/0.1/amp-story-auto-analytics.js
@@ -16,7 +16,7 @@
 
 import {Services} from '../../../src/services';
 import {buildGtagConfig} from './auto-analytics-configs.js';
-import {devAssert} from '../../../src/log';
+import {pureDevAssert as devAssert} from '../../../src/pure-assert';
 import {htmlFor} from '../../../src/static-template';
 
 const buildAutoAnalyticsTemplate = (element) => {
diff --git a/extensions/amp-story/1.0/pagination-buttons.js b/extensions/amp-story/1.0/pagination-buttons.js
index ae095e13ca89..2c2305890dd0 100644
--- a/extensions/amp-story/1.0/pagination-buttons.js
+++ b/extensions/amp-story/1.0/pagination-buttons.js
@@ -23,8 +23,8 @@ import {AdvancementMode} from './story-analytics';
 import {CommonSignals} from '../../../src/common-signals';
 import {EventType, dispatch} from './events';
 import {Services} from '../../../src/services';
-import {dev, devAssert} from '../../../src/log';
-
+import {dev} from '../../../src/log';
+import {pureDevAssert as devAssert} from '../../../src/pure-assert';
 import {htmlFor} from '../../../src/static-template';
 
 /** @struct @typedef {{className: string, triggers: (string|undefined)}} */
diff --git a/extensions/amp-story/1.0/simple-template.js b/extensions/amp-story/1.0/simple-template.js
index e58cf765aec7..d825ed23faa2 100644
--- a/extensions/amp-story/1.0/simple-template.js
+++ b/extensions/amp-story/1.0/simple-template.js
@@ -15,7 +15,7 @@
  */
 import {LocalizedStringId} from '../../../src/localized-strings'; // eslint-disable-line no-unused-vars
 import {createElementWithAttributes} from '../../../src/dom';
-import {devAssert} from '../../../src/log';
+import {pureDevAssert as devAssert} from '../../../src/pure-assert';
 import {getLocalizationService} from './amp-story-localization-service';
 import {hasOwn} from '../../../src/utils/object';
 import {isArray} from '../../../src/types';
diff --git a/extensions/amp-truncate-text/0.1/binary-search.js b/extensions/amp-truncate-text/0.1/binary-search.js
index 2b3cee5bd59d..861dffc608b7 100644
--- a/extensions/amp-truncate-text/0.1/binary-search.js
+++ b/extensions/amp-truncate-text/0.1/binary-search.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {devAssert} from '../../../src/log';
+import {pureDevAssert as devAssert} from '../../../src/pure-assert';
 
 /**
  * When no matching index is found, whether to stop on the next or previous
diff --git a/extensions/amp-viewer-integration/0.1/findtext.js b/extensions/amp-viewer-integration/0.1/findtext.js
index 29126c39dcb4..637d16bf80b1 100644
--- a/extensions/amp-viewer-integration/0.1/findtext.js
+++ b/extensions/amp-viewer-integration/0.1/findtext.js
@@ -15,7 +15,7 @@
  */
 
 import {computedStyle} from '../../../src/style';
-import {devAssert} from '../../../src/log';
+import {pureDevAssert as devAssert} from '../../../src/pure-assert';
 
 /**
  * Simple implementation of CircularBuffer.
diff --git a/src/action-constants.js b/src/action-constants.js
index e9ce3cfb0e79..452d353e998d 100644
--- a/src/action-constants.js
+++ b/src/action-constants.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {devAssert} from './log';
+import {pureDevAssert as devAssert} from './pure-assert';
 
 /**
  * Key string in an action arguments map for an unparsed object literal string.
diff --git a/src/context/component-hooks.js b/src/context/component-hooks.js
index dd85d364e30d..0f71e6e89336 100644
--- a/src/context/component-hooks.js
+++ b/src/context/component-hooks.js
@@ -15,7 +15,7 @@
  */
 
 import {areEqualOrdered} from '../utils/array';
-import {devAssert} from '../log';
+import {pureDevAssert as devAssert} from '../pure-assert';
 import {tryCallback} from './scheduler';
 
 const EMPTY_DEPS = [];
diff --git a/src/context/node.js b/src/context/node.js
index 4a18ca0c5c92..d81a31f8b1af 100644
--- a/src/context/node.js
+++ b/src/context/node.js
@@ -15,7 +15,7 @@
  */
 
 import {Values} from './values';
-import {devAssert} from '../log';
+import {pureDevAssert as devAssert} from '../pure-assert';
 import {getMode} from '../mode';
 import {pushIfNotExist, removeItem} from '../utils/array';
 import {throttleTail} from './scheduler';
diff --git a/src/context/prop.js b/src/context/prop.js
index 055a523e6a53..a579c64380f8 100644
--- a/src/context/prop.js
+++ b/src/context/prop.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {devAssert} from '../log';
+import {pureDevAssert as devAssert} from '../pure-assert';
 
 const EMPTY_DEPS = [];
 
diff --git a/src/css.js b/src/css.js
index e14b105ae196..083a23015a8f 100644
--- a/src/css.js
+++ b/src/css.js
@@ -15,7 +15,7 @@
  */
 
 import {cssEscape} from '../third_party/css-escape/css-escape';
-import {devAssert} from './log';
+import {pureDevAssert as devAssert} from './pure-assert';
 
 /**
  * Asserts that name is just an alphanumeric word, and does not contain
diff --git a/src/extension-analytics.js b/src/extension-analytics.js
index dfb15cf7087b..9fc182a4b259 100644
--- a/src/extension-analytics.js
+++ b/src/extension-analytics.js
@@ -17,7 +17,7 @@
 import {CommonSignals} from './common-signals';
 import {Services} from './services';
 import {createElementWithAttributes, removeElement} from './dom';
-import {devAssert} from './log';
+import {pureDevAssert as devAssert} from './pure-assert';
 import {dict} from './utils/object';
 import {isArray, toWin} from './types';
 import {triggerAnalyticsEvent} from './analytics';
diff --git a/src/finite-state-machine.js b/src/finite-state-machine.js
index c79ac03e66c7..ce33ba51c75d 100644
--- a/src/finite-state-machine.js
+++ b/src/finite-state-machine.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {devAssert} from './log';
+import {pureDevAssert as devAssert} from './pure-assert';
 
 /**
  * @template STATE
diff --git a/src/gesture.js b/src/gesture.js
index d1e8d0604d6b..860b5d189fdb 100644
--- a/src/gesture.js
+++ b/src/gesture.js
@@ -16,7 +16,7 @@
 
 import {Observable} from './observable';
 import {Pass} from './pass';
-import {devAssert} from './log';
+import {pureDevAssert as devAssert} from './pure-assert';
 import {findIndex} from './utils/array';
 import {supportsPassiveEventListener} from './event-helper-listen';
 import {toWin} from './types';
diff --git a/src/modal.js b/src/modal.js
index c2dbcd581f1a..8e7e30a9810c 100644
--- a/src/modal.js
+++ b/src/modal.js
@@ -1,4 +1,4 @@
-import {devAssert} from './log';
+import {pureDevAssert as devAssert} from './pure-assert';
 import {isConnectedNode, rootNodeFor} from './dom';
 import {toArray} from './types';
 
diff --git a/src/preact/base-element.js b/src/preact/base-element.js
index ca63e5fbbcb5..248a7d5d148f 100644
--- a/src/preact/base-element.js
+++ b/src/preact/base-element.js
@@ -40,7 +40,7 @@ import {
   parseBooleanAttribute,
 } from '../dom';
 import {dashToCamelCase} from '../string';
-import {devAssert} from '../log';
+import {pureDevAssert as devAssert} from '../pure-assert';
 import {dict, hasOwn, map} from '../utils/object';
 import {getDate} from '../utils/date';
 import {getMode} from '../mode';
diff --git a/src/render-delaying-services.js b/src/render-delaying-services.js
index 84c8da4058bc..8b4b912614ae 100644
--- a/src/render-delaying-services.js
+++ b/src/render-delaying-services.js
@@ -15,7 +15,7 @@
  */
 
 import {Services} from './services';
-import {devAssert} from './log';
+import {pureDevAssert as devAssert} from './pure-assert';
 import {getServicePromise} from './service';
 
 /**
diff --git a/src/service/core-services.js b/src/service/core-services.js
index 7f245f54ba88..e581d0d4cfec 100644
--- a/src/service/core-services.js
+++ b/src/service/core-services.js
@@ -15,7 +15,7 @@
  */
 
 import {adoptServiceForEmbedDoc} from '../service';
-import {devAssert} from '../log';
+import {pureDevAssert as devAssert} from '../pure-assert';
 import {installActionServiceForDoc} from './action-impl';
 import {installBatchedXhrService} from './batched-xhr-impl';
 import {installCidService} from './cid-impl';
diff --git a/src/service/hidden-observer-impl.js b/src/service/hidden-observer-impl.js
index 0c683d28c091..8c37adaa9ae5 100644
--- a/src/service/hidden-observer-impl.js
+++ b/src/service/hidden-observer-impl.js
@@ -15,7 +15,7 @@
  */
 
 import {Observable} from '../observable';
-import {devAssert} from '../log';
+import {pureDevAssert as devAssert} from '../pure-assert';
 import {registerServiceBuilderForDoc} from '../service';
 
 /**
diff --git a/src/service/owners-impl.js b/src/service/owners-impl.js
index 960e49545cc8..96d154208a77 100644
--- a/src/service/owners-impl.js
+++ b/src/service/owners-impl.js
@@ -17,7 +17,7 @@
 import {OwnersInterface} from './owners-interface';
 import {Resource} from './resource';
 import {Services} from '../services';
-import {devAssert} from '../log';
+import {pureDevAssert as devAssert} from '../pure-assert';
 import {isArray} from '../types';
 import {registerServiceBuilderForDoc} from '../service';
 
diff --git a/src/service/position-observer/position-observer-worker.js b/src/service/position-observer/position-observer-worker.js
index 727e0de0ed17..9d3e2b332cff 100644
--- a/src/service/position-observer/position-observer-worker.js
+++ b/src/service/position-observer/position-observer-worker.js
@@ -15,7 +15,7 @@
  */
 
 import {Services} from '../../services';
-import {devAssert} from '../../log';
+import {pureDevAssert as devAssert} from '../../pure-assert';
 import {
   layoutRectEquals,
   layoutRectLtwh,
diff --git a/src/service/task-queue.js b/src/service/task-queue.js
index 61cba6b97fb0..feb2a9a37eac 100644
--- a/src/service/task-queue.js
+++ b/src/service/task-queue.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {devAssert} from '../log';
+import {pureDevAssert as devAssert} from '../pure-assert';
 
 /**
  * The internal structure for the task.
diff --git a/src/service/variable-source.js b/src/service/variable-source.js
index f0023c6f9f43..3602faadc8be 100644
--- a/src/service/variable-source.js
+++ b/src/service/variable-source.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 import {Services} from '../services';
-import {devAssert} from '../log';
+import {pureDevAssert as devAssert} from '../pure-assert';
 import {isAmp4Email} from '../format';
 import {isFiniteNumber} from '../types';
 import {loadPromise} from '../event-helper';
diff --git a/src/static-template.js b/src/static-template.js
index 7bd952dc8ddf..69ca1d5e2600 100644
--- a/src/static-template.js
+++ b/src/static-template.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {devAssert} from './log';
+import {pureDevAssert as devAssert} from './pure-assert';
 import {map} from './utils/object.js';
 
 let htmlContainer;
diff --git a/src/utils/bytes.js b/src/utils/bytes.js
index de1b2954be8f..e38ce5ffb244 100644
--- a/src/utils/bytes.js
+++ b/src/utils/bytes.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {devAssert} from '../log';
+import {pureDevAssert as devAssert} from '../pure-assert';
 
 /**
  * Interpret a byte array as a UTF-8 string.
diff --git a/src/utils/detached-dom-stream.js b/src/utils/detached-dom-stream.js
index 63a46cc155c0..de0c3ecf76a9 100644
--- a/src/utils/detached-dom-stream.js
+++ b/src/utils/detached-dom-stream.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {devAssert} from '../log';
+import {pureDevAssert as devAssert} from '../pure-assert';
 
 export class DetachedDomStream {
   /**
diff --git a/src/utils/math.js b/src/utils/math.js
index dd3682d211e8..3b9953066482 100644
--- a/src/utils/math.js
+++ b/src/utils/math.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {devAssert} from '../log';
+import {pureDevAssert as devAssert} from '../pure-assert';
 
 /**
  * Maps a value in a first range to its equivalent in a second range
diff --git a/src/viewport-observer.js b/src/viewport-observer.js
index d76e03696d7f..d8db36e01194 100644
--- a/src/viewport-observer.js
+++ b/src/viewport-observer.js
@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-import {devAssert} from '../src/log';
+import {pureDevAssert as devAssert} from '../src/pure-assert';
 import {getMode} from './mode';
 import {isIframed} from './dom';
 import {toWin} from './types';

From f0b4a791fadab7f43eac2823d04cbda8e176c182 Mon Sep 17 00:00:00 2001
From: Ryan Cebulko <ryan@cebulko.com>
Date: Mon, 22 Feb 2021 12:06:41 -0500
Subject: [PATCH 08/15] Update all single imports of userAssert to use
 standalone helper

---
 3p/facebook.js                                                  | 2 +-
 3p/github.js                                                    | 2 +-
 3p/mathml.js                                                    | 2 +-
 .../__component_version__/amp-__component_name_hyphenated__.js  | 2 +-
 contributing/building-a-bento-amp-extension.md                  | 2 +-
 contributing/building-an-amp-extension.md                       | 2 +-
 extensions/amp-accordion/1.0/amp-accordion.js                   | 2 +-
 extensions/amp-action-macro/0.1/amp-action-macro.js             | 2 +-
 extensions/amp-ad-exit/0.1/filters/click-location.js            | 2 +-
 extensions/amp-ad/0.1/amp-ad-custom.js                          | 2 +-
 extensions/amp-ad/0.1/amp-ad.js                                 | 2 +-
 extensions/amp-addthis/0.1/amp-addthis.js                       | 2 +-
 extensions/amp-animation/0.1/runners/utils.js                   | 2 +-
 extensions/amp-auto-ads/0.1/amp-auto-ads.js                     | 2 +-
 extensions/amp-autocomplete/0.1/autocomplete-binding-inline.js  | 2 +-
 extensions/amp-base-carousel/1.0/amp-base-carousel.js           | 2 +-
 .../amp-bodymovin-animation/0.1/amp-bodymovin-animation.js      | 2 +-
 extensions/amp-carousel/0.1/base-slides.js                      | 2 +-
 extensions/amp-connatix-player/0.1/amp-connatix-player.js       | 2 +-
 extensions/amp-delight-player/0.1/amp-delight-player.js         | 2 +-
 extensions/amp-embedly-card/0.1/amp-embedly-card-impl.js        | 2 +-
 extensions/amp-embedly-card/0.1/amp-embedly-key.js              | 2 +-
 extensions/amp-experiment/1.0/mutation-record.js                | 2 +-
 extensions/amp-experiment/1.0/mutation/mutation.js              | 2 +-
 extensions/amp-fit-text/1.0/amp-fit-text.js                     | 2 +-
 .../amp-fx-collection/0.1/providers/amp-fx-presets-utils.js     | 2 +-
 extensions/amp-gwd-animation/0.1/amp-gwd-animation.js           | 2 +-
 extensions/amp-imgur/0.1/amp-imgur.js                           | 2 +-
 .../amp-inline-gallery/1.0/amp-inline-gallery-pagination.js     | 2 +-
 .../amp-inline-gallery/1.0/amp-inline-gallery-thumbnails.js     | 2 +-
 extensions/amp-inline-gallery/1.0/amp-inline-gallery.js         | 2 +-
 extensions/amp-inputmask/0.1/text-mask.js                       | 2 +-
 extensions/amp-instagram/0.1/amp-instagram.js                   | 2 +-
 extensions/amp-instagram/1.0/amp-instagram.js                   | 2 +-
 extensions/amp-kaltura-player/0.1/amp-kaltura-player.js         | 2 +-
 extensions/amp-lightbox/1.0/amp-lightbox.js                     | 2 +-
 extensions/amp-live-list/0.1/live-list-manager.js               | 2 +-
 extensions/amp-megaphone/0.1/amp-megaphone.js                   | 2 +-
 extensions/amp-o2-player/0.1/amp-o2-player.js                   | 2 +-
 .../amp-orientation-observer/0.1/amp-orientation-observer.js    | 2 +-
 extensions/amp-pinterest/0.1/follow-button.js                   | 2 +-
 extensions/amp-recaptcha-input/0.1/amp-recaptcha-input.js       | 2 +-
 extensions/amp-redbull-player/0.1/amp-redbull-player.js         | 2 +-
 extensions/amp-reddit/0.1/amp-reddit.js                         | 2 +-
 extensions/amp-riddle-quiz/0.1/amp-riddle-quiz.js               | 2 +-
 extensions/amp-selector/1.0/amp-selector.js                     | 2 +-
 extensions/amp-sidebar/1.0/amp-sidebar.js                       | 2 +-
 extensions/amp-skimlinks/0.1/link-rewriter/link-rewriter.js     | 2 +-
 extensions/amp-skimlinks/0.1/skim-options.js                    | 2 +-
 extensions/amp-social-share/1.0/amp-social-share.js             | 2 +-
 extensions/amp-soundcloud/0.1/amp-soundcloud.js                 | 2 +-
 extensions/amp-springboard-player/0.1/amp-springboard-player.js | 2 +-
 extensions/amp-story/1.0/animation-presets.js                   | 2 +-
 extensions/amp-story/1.0/bookend/components/article.js          | 2 +-
 extensions/amp-story/1.0/bookend/components/cta-link.js         | 2 +-
 extensions/amp-story/1.0/bookend/components/heading.js          | 2 +-
 extensions/amp-story/1.0/bookend/components/landscape.js        | 2 +-
 extensions/amp-story/1.0/bookend/components/portrait.js         | 2 +-
 extensions/amp-story/1.0/bookend/components/text-box.js         | 2 +-
 extensions/amp-story/1.0/live-story-manager.js                  | 2 +-
 extensions/amp-stream-gallery/1.0/amp-stream-gallery.js         | 2 +-
 extensions/amp-timeago/0.1/amp-timeago.js                       | 2 +-
 extensions/amp-timeago/1.0/amp-timeago.js                       | 2 +-
 extensions/amp-video/1.0/amp-video.js                           | 2 +-
 extensions/amp-vimeo/0.1/amp-vimeo.js                           | 2 +-
 extensions/amp-vine/0.1/amp-vine.js                             | 2 +-
 extensions/amp-yotpo/0.1/amp-yotpo.js                           | 2 +-
 extensions/amp-youtube/1.0/amp-youtube.js                       | 2 +-
 src/cookies.js                                                  | 2 +-
 src/element-service.js                                          | 2 +-
 src/service/custom-element-registry.js                          | 2 +-
 src/service/template-impl.js                                    | 2 +-
 src/ssr-template-helper.js                                      | 2 +-
 src/url.js                                                      | 2 +-
 74 files changed, 74 insertions(+), 74 deletions(-)

diff --git a/3p/facebook.js b/3p/facebook.js
index 834c16a011ab..5afe609195bc 100644
--- a/3p/facebook.js
+++ b/3p/facebook.js
@@ -18,7 +18,7 @@ import {dashToUnderline} from '../src/string';
 import {dict} from '../src/utils/object';
 import {loadScript} from './3p';
 import {setStyle} from '../src/style';
-import {userAssert} from '../src/log';
+import {pureUserAssert as userAssert} from '../src/pure-assert';
 
 /**
  * Produces the Facebook SDK object for the passed in callback.
diff --git a/3p/github.js b/3p/github.js
index fc646ccf40d4..04931b887248 100644
--- a/3p/github.js
+++ b/3p/github.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {userAssert} from '../src/log';
+import {pureUserAssert as userAssert} from '../src/pure-assert';
 import {writeScript} from './3p';
 
 /**
diff --git a/3p/mathml.js b/3p/mathml.js
index 8231a28e2a36..3792aab27062 100644
--- a/3p/mathml.js
+++ b/3p/mathml.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 import {setStyle} from '../src/style';
-import {userAssert} from '../src/log';
+import {pureUserAssert as userAssert} from '../src/pure-assert';
 import {writeScript} from './3p';
 
 /**
diff --git a/build-system/tasks/extension-generator/bento/amp-__component_name_hyphenated__/__component_version__/amp-__component_name_hyphenated__.js b/build-system/tasks/extension-generator/bento/amp-__component_name_hyphenated__/__component_version__/amp-__component_name_hyphenated__.js
index f8205cb7d9cc..ed83d640a334 100644
--- a/build-system/tasks/extension-generator/bento/amp-__component_name_hyphenated__/__component_version__/amp-__component_name_hyphenated__.js
+++ b/build-system/tasks/extension-generator/bento/amp-__component_name_hyphenated__/__component_version__/amp-__component_name_hyphenated__.js
@@ -18,7 +18,7 @@ import {BaseElement} from './base-element';
 import {CSS} from '../../../build/amp-__component_name_hyphenated__-__component_version__.css';
 import {dict} from '../../../src/utils/object';
 import {isExperimentOn} from '../../../src/experiments';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /** @const {string} */
 const TAG = 'amp-__component_name_hyphenated__';
diff --git a/contributing/building-a-bento-amp-extension.md b/contributing/building-a-bento-amp-extension.md
index 7502832bf0df..6bcded1259f5 100644
--- a/contributing/building-a-bento-amp-extension.md
+++ b/contributing/building-a-bento-amp-extension.md
@@ -484,7 +484,7 @@ Then protect your code with a check for the component-specific flag `isExperimen
 ```javascript
 import {CSS} from '../../../build/amp-my-element-0.1.css';
 import {isExperimentOn} from '../../../src/experiments';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /** @const */
 const TAG = 'amp-my-element';
diff --git a/contributing/building-an-amp-extension.md b/contributing/building-an-amp-extension.md
index 9ea47638cad7..1e0c10c66f29 100644
--- a/contributing/building-an-amp-extension.md
+++ b/contributing/building-an-amp-extension.md
@@ -659,7 +659,7 @@ And then protecting your code with a check `isExperimentOn(win, 'amp-my-element'
 
 ```javascript
 import {isExperimentOn} from '../../../src/experiments';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /** @const */
 const EXPERIMENT = 'amp-my-element';
diff --git a/extensions/amp-accordion/1.0/amp-accordion.js b/extensions/amp-accordion/1.0/amp-accordion.js
index c6875e1c6158..2a579bb7c428 100644
--- a/extensions/amp-accordion/1.0/amp-accordion.js
+++ b/extensions/amp-accordion/1.0/amp-accordion.js
@@ -21,7 +21,7 @@ import {Services} from '../../../src/services';
 import {createCustomEvent} from '../../../src/event-helper';
 import {isExperimentOn} from '../../../src/experiments';
 import {toWin} from '../../../src/types';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /** @const {string} */
 const TAG = 'amp-accordion';
diff --git a/extensions/amp-action-macro/0.1/amp-action-macro.js b/extensions/amp-action-macro/0.1/amp-action-macro.js
index 920a7e039cff..5870f88a2ae7 100644
--- a/extensions/amp-action-macro/0.1/amp-action-macro.js
+++ b/extensions/amp-action-macro/0.1/amp-action-macro.js
@@ -15,7 +15,7 @@
  */
 import {LayoutPriority} from '../../../src/layout';
 import {Services} from '../../../src/services';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /** @const {string} */
 const TAG = 'amp-action-macro';
diff --git a/extensions/amp-ad-exit/0.1/filters/click-location.js b/extensions/amp-ad-exit/0.1/filters/click-location.js
index 07253550a2cb..2ba5c31a7ebf 100644
--- a/extensions/amp-ad-exit/0.1/filters/click-location.js
+++ b/extensions/amp-ad-exit/0.1/filters/click-location.js
@@ -15,7 +15,7 @@
  */
 
 import {Filter, FilterType} from './filter';
-import {userAssert} from '../../../../src/log';
+import {pureUserAssert as userAssert} from '../../../../src/pure-assert';
 
 export class ClickLocationFilter extends Filter {
   /**
diff --git a/extensions/amp-ad/0.1/amp-ad-custom.js b/extensions/amp-ad/0.1/amp-ad-custom.js
index 2724259d643f..b5dd6441bcf8 100644
--- a/extensions/amp-ad/0.1/amp-ad-custom.js
+++ b/extensions/amp-ad/0.1/amp-ad-custom.js
@@ -25,7 +25,7 @@ import {
   removeChildren,
 } from '../../../src/dom';
 import {hasOwn} from '../../../src/utils/object';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /** @const {string} Tag name for custom ad implementation. */
 export const TAG_AD_CUSTOM = 'amp-ad-custom';
diff --git a/extensions/amp-ad/0.1/amp-ad.js b/extensions/amp-ad/0.1/amp-ad.js
index 741fc29e8e59..690930858c40 100644
--- a/extensions/amp-ad/0.1/amp-ad.js
+++ b/extensions/amp-ad/0.1/amp-ad.js
@@ -20,7 +20,7 @@ import {Services} from '../../../src/services';
 import {adConfig} from '../../../ads/_config';
 import {getA4ARegistry} from '../../../ads/_a4a-config';
 import {hasOwn} from '../../../src/utils/object';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /**
  * Construct ad network type-specific tag and script name.  Note that this
diff --git a/extensions/amp-addthis/0.1/amp-addthis.js b/extensions/amp-addthis/0.1/amp-addthis.js
index 2ccb457be94b..364df95ab3b8 100644
--- a/extensions/amp-addthis/0.1/amp-addthis.js
+++ b/extensions/amp-addthis/0.1/amp-addthis.js
@@ -70,7 +70,7 @@ import {isLayoutSizeDefined} from '../../../src/layout';
 import {listen} from '../../../src/event-helper';
 import {parseUrlDeprecated} from '../../../src/url';
 import {setStyle} from '../../../src/style';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 // The following items will be shared by all AmpAddThis elements on a page, to
 // prevent unnecessary HTTP requests, get accurate analytics, etc., and hence
diff --git a/extensions/amp-animation/0.1/runners/utils.js b/extensions/amp-animation/0.1/runners/utils.js
index 63089c26d8f5..c618b3b50de3 100644
--- a/extensions/amp-animation/0.1/runners/utils.js
+++ b/extensions/amp-animation/0.1/runners/utils.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {userAssert} from '../../../../src/log';
+import {pureUserAssert as userAssert} from '../../../../src/pure-assert';
 
 /**
  * @param {!Array<!../web-animation-types.InternalWebAnimationRequestDef>} requests
diff --git a/extensions/amp-auto-ads/0.1/amp-auto-ads.js b/extensions/amp-auto-ads/0.1/amp-auto-ads.js
index e692b4e48e9e..cc4c7ac035dd 100644
--- a/extensions/amp-auto-ads/0.1/amp-auto-ads.js
+++ b/extensions/amp-auto-ads/0.1/amp-auto-ads.js
@@ -27,7 +27,7 @@ import {dict} from '../../../src/utils/object';
 import {getAdNetworkConfig} from './ad-network-config';
 import {getPlacementsFromConfigObj} from './placement';
 import {isExperimentOn} from '../../../src/experiments';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /** @const */
 const TAG = 'amp-auto-ads';
diff --git a/extensions/amp-autocomplete/0.1/autocomplete-binding-inline.js b/extensions/amp-autocomplete/0.1/autocomplete-binding-inline.js
index 36a9d3c1ab00..7626eb3fd91e 100644
--- a/extensions/amp-autocomplete/0.1/autocomplete-binding-inline.js
+++ b/extensions/amp-autocomplete/0.1/autocomplete-binding-inline.js
@@ -16,7 +16,7 @@
 
 import {ownProperty} from '../../../src/utils/object';
 import {tryFocus} from '../../../src/dom';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 const TAG = 'amp-autocomplete';
 
diff --git a/extensions/amp-base-carousel/1.0/amp-base-carousel.js b/extensions/amp-base-carousel/1.0/amp-base-carousel.js
index 2f0006cb8545..d58c28587afc 100644
--- a/extensions/amp-base-carousel/1.0/amp-base-carousel.js
+++ b/extensions/amp-base-carousel/1.0/amp-base-carousel.js
@@ -25,7 +25,7 @@ import {createCustomEvent} from '../../../src/event-helper';
 import {dict} from '../../../src/utils/object';
 import {dispatchCustomEvent} from '../../../src/dom';
 import {isExperimentOn} from '../../../src/experiments';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /** @const {string} */
 const TAG = 'amp-base-carousel';
diff --git a/extensions/amp-bodymovin-animation/0.1/amp-bodymovin-animation.js b/extensions/amp-bodymovin-animation/0.1/amp-bodymovin-animation.js
index d19e1a1ef725..212dbd66a35b 100644
--- a/extensions/amp-bodymovin-animation/0.1/amp-bodymovin-animation.js
+++ b/extensions/amp-bodymovin-animation/0.1/amp-bodymovin-animation.js
@@ -27,7 +27,7 @@ import {isFiniteNumber, isObject} from '../../../src/types';
 import {isLayoutSizeDefined} from '../../../src/layout';
 import {parseJson} from '../../../src/json';
 import {removeElement} from '../../../src/dom';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 const TAG = 'amp-bodymovin-animation';
 
diff --git a/extensions/amp-carousel/0.1/base-slides.js b/extensions/amp-carousel/0.1/base-slides.js
index 1deeb0f19472..83883b56ebc2 100644
--- a/extensions/amp-carousel/0.1/base-slides.js
+++ b/extensions/amp-carousel/0.1/base-slides.js
@@ -18,7 +18,7 @@ import {ActionTrust} from '../../../src/action-constants';
 import {BaseCarousel} from './base-carousel';
 import {Services} from '../../../src/services';
 import {isFiniteNumber} from '../../../src/types';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 export class BaseSlides extends BaseCarousel {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-connatix-player/0.1/amp-connatix-player.js b/extensions/amp-connatix-player/0.1/amp-connatix-player.js
index deba334354eb..c41fe83bed37 100644
--- a/extensions/amp-connatix-player/0.1/amp-connatix-player.js
+++ b/extensions/amp-connatix-player/0.1/amp-connatix-player.js
@@ -37,7 +37,7 @@ import {
 import {removeElement} from '../../../src/dom';
 import {setIsMediaComponent} from '../../../src/video-interface';
 import {tryParseJson} from '../../../src/json';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /**
  * @param {!Array<T>} promises
diff --git a/extensions/amp-delight-player/0.1/amp-delight-player.js b/extensions/amp-delight-player/0.1/amp-delight-player.js
index e243c78c38c2..1e16a91529be 100644
--- a/extensions/amp-delight-player/0.1/amp-delight-player.js
+++ b/extensions/amp-delight-player/0.1/amp-delight-player.js
@@ -40,7 +40,7 @@ import {
   unobserveWithSharedInOb,
 } from '../../../src/viewport-observer';
 import {setStyle} from '../../../src/style';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /** @const */
 const TAG = 'amp-delight-player';
diff --git a/extensions/amp-embedly-card/0.1/amp-embedly-card-impl.js b/extensions/amp-embedly-card/0.1/amp-embedly-card-impl.js
index fb96b924d1d8..ebe9525a2872 100644
--- a/extensions/amp-embedly-card/0.1/amp-embedly-card-impl.js
+++ b/extensions/amp-embedly-card/0.1/amp-embedly-card-impl.js
@@ -20,7 +20,7 @@ import {Services} from '../../../src/services';
 import {getIframe} from '../../../src/3p-frame';
 import {listenFor} from '../../../src/iframe-helper';
 import {removeElement} from '../../../src/dom';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /**
  * Component tag identifier.
diff --git a/extensions/amp-embedly-card/0.1/amp-embedly-key.js b/extensions/amp-embedly-card/0.1/amp-embedly-key.js
index 4e67804690f7..793d4847d674 100644
--- a/extensions/amp-embedly-card/0.1/amp-embedly-key.js
+++ b/extensions/amp-embedly-card/0.1/amp-embedly-key.js
@@ -15,7 +15,7 @@
  */
 
 import {Layout} from '../../../src/layout';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /** @const {string} */
 export const TAG = 'amp-embedly-key';
diff --git a/extensions/amp-experiment/1.0/mutation-record.js b/extensions/amp-experiment/1.0/mutation-record.js
index cda6950ff033..268f3a84f484 100644
--- a/extensions/amp-experiment/1.0/mutation-record.js
+++ b/extensions/amp-experiment/1.0/mutation-record.js
@@ -15,7 +15,7 @@
  */
 
 import {isObject, toArray} from '../../../src/types';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /**
  * Types of possibile mutations
diff --git a/extensions/amp-experiment/1.0/mutation/mutation.js b/extensions/amp-experiment/1.0/mutation/mutation.js
index df0c2182d255..fa892ef7eff0 100644
--- a/extensions/amp-experiment/1.0/mutation/mutation.js
+++ b/extensions/amp-experiment/1.0/mutation/mutation.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {userAssert} from '../../../../src/log';
+import {pureUserAssert as userAssert} from '../../../../src/pure-assert';
 
 /**
  * Interface for amp-experiment mutations.
diff --git a/extensions/amp-fit-text/1.0/amp-fit-text.js b/extensions/amp-fit-text/1.0/amp-fit-text.js
index baf7d7338ce8..ac110d077c4e 100644
--- a/extensions/amp-fit-text/1.0/amp-fit-text.js
+++ b/extensions/amp-fit-text/1.0/amp-fit-text.js
@@ -17,7 +17,7 @@
 import {BaseElement} from './base-element';
 import {CSS} from '../../../build/amp-fit-text-1.0.css';
 import {isExperimentOn} from '../../../src/experiments';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /** @const {string} */
 const TAG = 'amp-fit-text';
diff --git a/extensions/amp-fx-collection/0.1/providers/amp-fx-presets-utils.js b/extensions/amp-fx-collection/0.1/providers/amp-fx-presets-utils.js
index a242d5858648..00630de3bf0a 100644
--- a/extensions/amp-fx-collection/0.1/providers/amp-fx-presets-utils.js
+++ b/extensions/amp-fx-collection/0.1/providers/amp-fx-presets-utils.js
@@ -22,7 +22,7 @@
 import {FxType} from '../fx-type';
 import {Services} from '../../../../src/services';
 import {mapRange} from '../../../../src/utils/math';
-import {userAssert} from '../../../../src/log';
+import {pureUserAssert as userAssert} from '../../../../src/pure-assert';
 
 const MAX_MOBILE_WIDTH = 480;
 const MAX_TABLET_WIDTH = 1000;
diff --git a/extensions/amp-gwd-animation/0.1/amp-gwd-animation.js b/extensions/amp-gwd-animation/0.1/amp-gwd-animation.js
index 1d074097085a..12d6b45840bd 100644
--- a/extensions/amp-gwd-animation/0.1/amp-gwd-animation.js
+++ b/extensions/amp-gwd-animation/0.1/amp-gwd-animation.js
@@ -27,7 +27,7 @@ import {
   getParentWindowFrameElement,
   getServiceForDocOrNull,
 } from '../../../src/service';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /**
  * Returns a value at any level in an object structure addressed by dot-notation
diff --git a/extensions/amp-imgur/0.1/amp-imgur.js b/extensions/amp-imgur/0.1/amp-imgur.js
index 251c0f892e9b..5c42f478f425 100644
--- a/extensions/amp-imgur/0.1/amp-imgur.js
+++ b/extensions/amp-imgur/0.1/amp-imgur.js
@@ -32,7 +32,7 @@ import {isLayoutSizeDefined} from '../../../src/layout';
 import {isObject} from '../../../src/types';
 import {removeElement} from '../../../src/dom';
 import {tryParseJson} from '../../../src/json';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 export class AmpImgur extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-inline-gallery/1.0/amp-inline-gallery-pagination.js b/extensions/amp-inline-gallery/1.0/amp-inline-gallery-pagination.js
index 706274f35260..78b197212043 100644
--- a/extensions/amp-inline-gallery/1.0/amp-inline-gallery-pagination.js
+++ b/extensions/amp-inline-gallery/1.0/amp-inline-gallery-pagination.js
@@ -19,7 +19,7 @@ import {CarouselContextProp} from '../../amp-base-carousel/1.0/carousel-props';
 import {Pagination} from './pagination';
 import {PreactBaseElement} from '../../../src/preact/base-element';
 import {isExperimentOn} from '../../../src/experiments';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /** @const {string} */
 export const TAG = 'amp-inline-gallery-pagination';
diff --git a/extensions/amp-inline-gallery/1.0/amp-inline-gallery-thumbnails.js b/extensions/amp-inline-gallery/1.0/amp-inline-gallery-thumbnails.js
index 08066e55d8c5..c1754602ca37 100644
--- a/extensions/amp-inline-gallery/1.0/amp-inline-gallery-thumbnails.js
+++ b/extensions/amp-inline-gallery/1.0/amp-inline-gallery-thumbnails.js
@@ -20,7 +20,7 @@ import {PreactBaseElement} from '../../../src/preact/base-element';
 import {CSS as THUMBNAIL_CSS} from './thumbnails.jss';
 import {Thumbnails} from './thumbnails';
 import {isExperimentOn} from '../../../src/experiments';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /** @const {string} */
 export const TAG = 'amp-inline-gallery-thumbnails';
diff --git a/extensions/amp-inline-gallery/1.0/amp-inline-gallery.js b/extensions/amp-inline-gallery/1.0/amp-inline-gallery.js
index a51401b508bf..e79322e829f9 100644
--- a/extensions/amp-inline-gallery/1.0/amp-inline-gallery.js
+++ b/extensions/amp-inline-gallery/1.0/amp-inline-gallery.js
@@ -32,7 +32,7 @@ import {dict} from '../../../src/utils/object';
 import {isExperimentOn} from '../../../src/experiments';
 import {setProp} from '../../../src/context';
 import {useContext, useLayoutEffect} from '../../../src/preact';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /** @const {string} */
 const TAG = 'amp-inline-gallery';
diff --git a/extensions/amp-inputmask/0.1/text-mask.js b/extensions/amp-inputmask/0.1/text-mask.js
index 4ab8464f5942..889c32cb9ae0 100644
--- a/extensions/amp-inputmask/0.1/text-mask.js
+++ b/extensions/amp-inputmask/0.1/text-mask.js
@@ -18,7 +18,7 @@ import {Mask} from './mask-impl';
 import {OutputMode} from './constants';
 import {Services} from '../../../src/services';
 import {iterateCursor, removeElement} from '../../../src/dom';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 const ELEMENT_MASK_PROPERTY = '__amp_inputmask_masked';
 const ELEMENT_MASK_OUTPUT_PROPERTY = '__amp_inputmask_hidden';
diff --git a/extensions/amp-instagram/0.1/amp-instagram.js b/extensions/amp-instagram/0.1/amp-instagram.js
index d5bc942ba689..849d939a50ea 100644
--- a/extensions/amp-instagram/0.1/amp-instagram.js
+++ b/extensions/amp-instagram/0.1/amp-instagram.js
@@ -43,7 +43,7 @@ import {isObject} from '../../../src/types';
 import {removeElement} from '../../../src/dom';
 import {setStyle} from '../../../src/style';
 import {tryParseJson} from '../../../src/json';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 export class AmpInstagram extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-instagram/1.0/amp-instagram.js b/extensions/amp-instagram/1.0/amp-instagram.js
index 45229c59287a..1346557662ac 100644
--- a/extensions/amp-instagram/1.0/amp-instagram.js
+++ b/extensions/amp-instagram/1.0/amp-instagram.js
@@ -18,7 +18,7 @@ import {BaseElement} from './base-element';
 import {CSS} from '../../../build/amp-instagram-1.0.css';
 import {dict} from '../../../src/utils/object';
 import {isExperimentOn} from '../../../src/experiments';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /** @const {string} */
 const TAG = 'amp-instagram';
diff --git a/extensions/amp-kaltura-player/0.1/amp-kaltura-player.js b/extensions/amp-kaltura-player/0.1/amp-kaltura-player.js
index a99915abd3a1..fc55a181745d 100644
--- a/extensions/amp-kaltura-player/0.1/amp-kaltura-player.js
+++ b/extensions/amp-kaltura-player/0.1/amp-kaltura-player.js
@@ -20,7 +20,7 @@ import {dict} from '../../../src/utils/object';
 import {getDataParamsFromAttributes} from '../../../src/dom';
 import {isLayoutSizeDefined} from '../../../src/layout';
 import {setIsMediaComponent} from '../../../src/video-interface';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 class AmpKaltura extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-lightbox/1.0/amp-lightbox.js b/extensions/amp-lightbox/1.0/amp-lightbox.js
index a74020a36abf..25075b0ba7bc 100644
--- a/extensions/amp-lightbox/1.0/amp-lightbox.js
+++ b/extensions/amp-lightbox/1.0/amp-lightbox.js
@@ -21,7 +21,7 @@ import {Services} from '../../../src/services';
 import {createCustomEvent} from '../../../src/event-helper';
 import {isExperimentOn} from '../../../src/experiments';
 import {toWin} from '../../../src/types';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /** @const {string} */
 const TAG = 'amp-lightbox';
diff --git a/extensions/amp-live-list/0.1/live-list-manager.js b/extensions/amp-live-list/0.1/live-list-manager.js
index d81d204a277e..b77d85d13c0a 100644
--- a/extensions/amp-live-list/0.1/live-list-manager.js
+++ b/extensions/amp-live-list/0.1/live-list-manager.js
@@ -21,7 +21,7 @@ import {fetchDocument} from '../../../src/document-fetcher';
 import {getMode} from '../../../src/mode';
 import {getServicePromiseForDoc} from '../../../src/service';
 import {toArray} from '../../../src/types';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /** @const {string} */
 export const SERVICE_ID = 'liveListManager';
diff --git a/extensions/amp-megaphone/0.1/amp-megaphone.js b/extensions/amp-megaphone/0.1/amp-megaphone.js
index ca99bf439157..43fe311c31f7 100644
--- a/extensions/amp-megaphone/0.1/amp-megaphone.js
+++ b/extensions/amp-megaphone/0.1/amp-megaphone.js
@@ -36,7 +36,7 @@ import {isObject} from '../../../src/types';
 import {removeElement} from '../../../src/dom';
 import {setIsMediaComponent} from '../../../src/video-interface';
 import {tryParseJson} from '../../../src/json';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 class AmpMegaphone extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-o2-player/0.1/amp-o2-player.js b/extensions/amp-o2-player/0.1/amp-o2-player.js
index d2fdeeb957e9..c87b4876004a 100644
--- a/extensions/amp-o2-player/0.1/amp-o2-player.js
+++ b/extensions/amp-o2-player/0.1/amp-o2-player.js
@@ -25,7 +25,7 @@ import {
 import {isLayoutSizeDefined} from '../../../src/layout';
 import {listenFor} from '../../../src/iframe-helper';
 import {setIsMediaComponent} from '../../../src/video-interface';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 class AmpO2Player extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-orientation-observer/0.1/amp-orientation-observer.js b/extensions/amp-orientation-observer/0.1/amp-orientation-observer.js
index 95ad712a5934..c273a93e40d9 100644
--- a/extensions/amp-orientation-observer/0.1/amp-orientation-observer.js
+++ b/extensions/amp-orientation-observer/0.1/amp-orientation-observer.js
@@ -19,7 +19,7 @@ import {Services} from '../../../src/services';
 import {clamp, sum} from '../../../src/utils/math';
 import {createCustomEvent} from '../../../src/event-helper';
 import {dict} from '../../../src/utils/object';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 const TAG = 'amp-orientation-observer';
 /**
diff --git a/extensions/amp-pinterest/0.1/follow-button.js b/extensions/amp-pinterest/0.1/follow-button.js
index 750ccb340748..e5d2fd4888da 100644
--- a/extensions/amp-pinterest/0.1/follow-button.js
+++ b/extensions/amp-pinterest/0.1/follow-button.js
@@ -19,7 +19,7 @@ import {assertHttpsUrl} from '../../../src/url';
 import {openWindowDialog} from '../../../src/dom';
 import {tryResolve} from '../../../src/utils/promise';
 
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 // Popup options
 const POP_FOLLOW = `status=no,resizable=yes,scrollbars=yes,
diff --git a/extensions/amp-recaptcha-input/0.1/amp-recaptcha-input.js b/extensions/amp-recaptcha-input/0.1/amp-recaptcha-input.js
index 5b21111b1273..e4d9b1cd5faf 100644
--- a/extensions/amp-recaptcha-input/0.1/amp-recaptcha-input.js
+++ b/extensions/amp-recaptcha-input/0.1/amp-recaptcha-input.js
@@ -31,7 +31,7 @@ import {
 import {CSS} from '../../../build/amp-recaptcha-input-0.1.css';
 import {Layout} from '../../../src/layout';
 import {setStyles, toggle} from '../../../src/style';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /** @const */
 const TAG = 'amp-recaptcha-input';
diff --git a/extensions/amp-redbull-player/0.1/amp-redbull-player.js b/extensions/amp-redbull-player/0.1/amp-redbull-player.js
index 87586214f15c..cae4ae6e60b6 100644
--- a/extensions/amp-redbull-player/0.1/amp-redbull-player.js
+++ b/extensions/amp-redbull-player/0.1/amp-redbull-player.js
@@ -33,7 +33,7 @@ import {
 import {getData, listen} from '../../../src/event-helper';
 import {installVideoManagerForDoc} from '../../../src/service/video-manager-impl';
 import {isLayoutSizeDefined} from '../../../src/layout';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /** @private @const */
 const TAG = 'amp-redbull-player';
diff --git a/extensions/amp-reddit/0.1/amp-reddit.js b/extensions/amp-reddit/0.1/amp-reddit.js
index 634a41bb8ab3..63e93faf2bc0 100644
--- a/extensions/amp-reddit/0.1/amp-reddit.js
+++ b/extensions/amp-reddit/0.1/amp-reddit.js
@@ -18,7 +18,7 @@ import {Services} from '../../../src/services';
 import {getIframe, preloadBootstrap} from '../../../src/3p-frame';
 import {isLayoutSizeDefined} from '../../../src/layout';
 import {listenFor} from '../../../src/iframe-helper';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 class AmpReddit extends AMP.BaseElement {
   /**
diff --git a/extensions/amp-riddle-quiz/0.1/amp-riddle-quiz.js b/extensions/amp-riddle-quiz/0.1/amp-riddle-quiz.js
index 0aec1871fbba..64c1b3275920 100644
--- a/extensions/amp-riddle-quiz/0.1/amp-riddle-quiz.js
+++ b/extensions/amp-riddle-quiz/0.1/amp-riddle-quiz.js
@@ -17,7 +17,7 @@ import {getData, listen} from './../../../src/event-helper';
 import {isFiniteNumber, isObject} from '../../../src/types';
 import {isLayoutSizeDefined} from '../../../src/layout';
 import {removeElement} from '../../../src/dom';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 export class AmpRiddleQuiz extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-selector/1.0/amp-selector.js b/extensions/amp-selector/1.0/amp-selector.js
index 877102ae4294..a6b3b5906efe 100644
--- a/extensions/amp-selector/1.0/amp-selector.js
+++ b/extensions/amp-selector/1.0/amp-selector.js
@@ -22,7 +22,7 @@ import {createCustomEvent} from '../../../src/event-helper';
 import {dict} from '../../../src/utils/object';
 import {isExperimentOn} from '../../../src/experiments';
 import {toWin} from '../../../src/types';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /** @const {string} */
 const TAG = 'amp-selector';
diff --git a/extensions/amp-sidebar/1.0/amp-sidebar.js b/extensions/amp-sidebar/1.0/amp-sidebar.js
index 4064b7fdcf40..b3725e5b4696 100644
--- a/extensions/amp-sidebar/1.0/amp-sidebar.js
+++ b/extensions/amp-sidebar/1.0/amp-sidebar.js
@@ -21,7 +21,7 @@ import {Sidebar} from './sidebar';
 import {dict} from '../../../src/utils/object';
 import {isExperimentOn} from '../../../src/experiments';
 import {toggle} from '../../../src/style';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /** @const {string} */
 const TAG = 'amp-sidebar';
diff --git a/extensions/amp-skimlinks/0.1/link-rewriter/link-rewriter.js b/extensions/amp-skimlinks/0.1/link-rewriter/link-rewriter.js
index f1ca64369fc8..86dff6348224 100644
--- a/extensions/amp-skimlinks/0.1/link-rewriter/link-rewriter.js
+++ b/extensions/amp-skimlinks/0.1/link-rewriter/link-rewriter.js
@@ -19,7 +19,7 @@ import {EVENTS, ORIGINAL_URL_ATTRIBUTE} from './constants';
 import {LinkReplacementCache} from './link-replacement-cache';
 import {Observable} from '../../../../src/observable';
 import {TwoStepsResponse} from './two-steps-response';
-import {userAssert} from '../../../../src/log';
+import {pureUserAssert as userAssert} from '../../../../src/pure-assert';
 
 /** @typedef {!Array<{anchor: !HTMLElement, replacementUrl: ?string}>}} */
 export let AnchorReplacementList;
diff --git a/extensions/amp-skimlinks/0.1/skim-options.js b/extensions/amp-skimlinks/0.1/skim-options.js
index 620ba552ffaa..64a1c4593686 100644
--- a/extensions/amp-skimlinks/0.1/skim-options.js
+++ b/extensions/amp-skimlinks/0.1/skim-options.js
@@ -16,7 +16,7 @@
 
 import {getChildJsonConfig} from '../../../src/json';
 import {getNormalizedHostnameFromUrl} from './utils';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 import {
   DEFAULT_CONFIG,
diff --git a/extensions/amp-social-share/1.0/amp-social-share.js b/extensions/amp-social-share/1.0/amp-social-share.js
index ef2f886bb9f0..342cfc89147a 100644
--- a/extensions/amp-social-share/1.0/amp-social-share.js
+++ b/extensions/amp-social-share/1.0/amp-social-share.js
@@ -26,7 +26,7 @@ import {getSocialConfig} from './social-share-config';
 import {isExperimentOn} from '../../../src/experiments';
 import {toWin} from '../../../src/types';
 import {toggle} from '../../../src/style';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /** @const {string} */
 const TAG = 'amp-social-share';
diff --git a/extensions/amp-soundcloud/0.1/amp-soundcloud.js b/extensions/amp-soundcloud/0.1/amp-soundcloud.js
index 69baf214bee5..85e13646c52e 100644
--- a/extensions/amp-soundcloud/0.1/amp-soundcloud.js
+++ b/extensions/amp-soundcloud/0.1/amp-soundcloud.js
@@ -31,7 +31,7 @@ import {Services} from '../../../src/services';
 import {dict} from '../../../src/utils/object';
 import {isLayoutSizeDefined} from '../../../src/layout';
 import {setIsMediaComponent} from '../../../src/video-interface';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 class AmpSoundcloud extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-springboard-player/0.1/amp-springboard-player.js b/extensions/amp-springboard-player/0.1/amp-springboard-player.js
index 10164511fce1..d6a591fe0eaf 100644
--- a/extensions/amp-springboard-player/0.1/amp-springboard-player.js
+++ b/extensions/amp-springboard-player/0.1/amp-springboard-player.js
@@ -17,7 +17,7 @@
 import {Services} from '../../../src/services';
 import {isLayoutSizeDefined} from '../../../src/layout';
 import {setIsMediaComponent} from '../../../src/video-interface';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 class AmpSpringboardPlayer extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-story/1.0/animation-presets.js b/extensions/amp-story/1.0/animation-presets.js
index ab6799df06f3..d6fa99607442 100644
--- a/extensions/amp-story/1.0/animation-presets.js
+++ b/extensions/amp-story/1.0/animation-presets.js
@@ -24,7 +24,7 @@ import {
   whooshIn,
 } from './animation-presets-utils';
 import {px} from '../../../src/style';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /** @const {string} */
 const FULL_BLEED_CATEGORY = 'full-bleed';
diff --git a/extensions/amp-story/1.0/bookend/components/article.js b/extensions/amp-story/1.0/bookend/components/article.js
index 09d0cf4e44dd..beedff817c52 100644
--- a/extensions/amp-story/1.0/bookend/components/article.js
+++ b/extensions/amp-story/1.0/bookend/components/article.js
@@ -28,7 +28,7 @@ import {
 } from '../../utils';
 import {getSourceUrl, resolveRelativeUrl} from '../../../../../src/url';
 import {htmlFor, htmlRefs} from '../../../../../src/static-template';
-import {userAssert} from '../../../../../src/log';
+import {pureUserAssert as userAssert} from '../../../../../src/pure-assert';
 
 /**
  * @typedef {{
diff --git a/extensions/amp-story/1.0/bookend/components/cta-link.js b/extensions/amp-story/1.0/bookend/components/cta-link.js
index 920880dc7432..1bd817f1c8c0 100644
--- a/extensions/amp-story/1.0/bookend/components/cta-link.js
+++ b/extensions/amp-story/1.0/bookend/components/cta-link.js
@@ -24,7 +24,7 @@ import {dict} from '../../../../../src/utils/object';
 import {getSourceUrl, resolveRelativeUrl} from '../../../../../src/url';
 import {htmlFor, htmlRefs} from '../../../../../src/static-template';
 import {isArray} from '../../../../../src/types';
-import {userAssert} from '../../../../../src/log';
+import {pureUserAssert as userAssert} from '../../../../../src/pure-assert';
 import {userAssertValidProtocol} from '../../utils';
 
 /**
diff --git a/extensions/amp-story/1.0/bookend/components/heading.js b/extensions/amp-story/1.0/bookend/components/heading.js
index 6440d1ce7807..22d060134581 100644
--- a/extensions/amp-story/1.0/bookend/components/heading.js
+++ b/extensions/amp-story/1.0/bookend/components/heading.js
@@ -20,7 +20,7 @@ import {
   BookendComponentInterface,
 } from './bookend-component-interface';
 import {htmlFor} from '../../../../../src/static-template';
-import {userAssert} from '../../../../../src/log';
+import {pureUserAssert as userAssert} from '../../../../../src/pure-assert';
 
 /**
  * @typedef {{
diff --git a/extensions/amp-story/1.0/bookend/components/landscape.js b/extensions/amp-story/1.0/bookend/components/landscape.js
index 4f4a75560450..eeb90bb99ddb 100644
--- a/extensions/amp-story/1.0/bookend/components/landscape.js
+++ b/extensions/amp-story/1.0/bookend/components/landscape.js
@@ -28,7 +28,7 @@ import {
 } from '../../utils';
 import {getSourceUrl, resolveRelativeUrl} from '../../../../../src/url';
 import {htmlFor, htmlRefs} from '../../../../../src/static-template';
-import {userAssert} from '../../../../../src/log';
+import {pureUserAssert as userAssert} from '../../../../../src/pure-assert';
 
 /**
  * @typedef {{
diff --git a/extensions/amp-story/1.0/bookend/components/portrait.js b/extensions/amp-story/1.0/bookend/components/portrait.js
index 1fa2591389c8..a161b6b1e756 100644
--- a/extensions/amp-story/1.0/bookend/components/portrait.js
+++ b/extensions/amp-story/1.0/bookend/components/portrait.js
@@ -28,7 +28,7 @@ import {
 } from '../../utils';
 import {getSourceUrl, resolveRelativeUrl} from '../../../../../src/url';
 import {htmlFor, htmlRefs} from '../../../../../src/static-template';
-import {userAssert} from '../../../../../src/log';
+import {pureUserAssert as userAssert} from '../../../../../src/pure-assert';
 
 /**
  * @typedef {{
diff --git a/extensions/amp-story/1.0/bookend/components/text-box.js b/extensions/amp-story/1.0/bookend/components/text-box.js
index 2e2c787c8b20..22e1b558965e 100644
--- a/extensions/amp-story/1.0/bookend/components/text-box.js
+++ b/extensions/amp-story/1.0/bookend/components/text-box.js
@@ -21,7 +21,7 @@ import {
 } from './bookend-component-interface';
 import {htmlFor} from '../../../../../src/static-template';
 import {isArray} from '../../../../../src/types';
-import {userAssert} from '../../../../../src/log';
+import {pureUserAssert as userAssert} from '../../../../../src/pure-assert';
 
 /**
  * @typedef {{
diff --git a/extensions/amp-story/1.0/live-story-manager.js b/extensions/amp-story/1.0/live-story-manager.js
index 1cbe43e9d871..7b3a07fcc4e1 100644
--- a/extensions/amp-story/1.0/live-story-manager.js
+++ b/extensions/amp-story/1.0/live-story-manager.js
@@ -19,7 +19,7 @@ import {CommonSignals} from '../../../src/common-signals';
 import {Services} from '../../../src/services';
 import {createElementWithAttributes, lastChildElement} from '../../../src/dom';
 import {dict} from '../../../src/utils/object';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /**
  * Property used for storing id of custom slot. This custom slot can be used to
diff --git a/extensions/amp-stream-gallery/1.0/amp-stream-gallery.js b/extensions/amp-stream-gallery/1.0/amp-stream-gallery.js
index 75a7c7cc69eb..ff595047e026 100644
--- a/extensions/amp-stream-gallery/1.0/amp-stream-gallery.js
+++ b/extensions/amp-stream-gallery/1.0/amp-stream-gallery.js
@@ -25,7 +25,7 @@ import {createCustomEvent} from '../../../src/event-helper';
 import {dict} from '../../../src/utils/object';
 import {dispatchCustomEvent} from '../../../src/dom';
 import {isExperimentOn} from '../../../src/experiments';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /** @const {string} */
 const TAG = 'amp-stream-gallery';
diff --git a/extensions/amp-timeago/0.1/amp-timeago.js b/extensions/amp-timeago/0.1/amp-timeago.js
index b22c28e30219..f3c98166a2dc 100644
--- a/extensions/amp-timeago/0.1/amp-timeago.js
+++ b/extensions/amp-timeago/0.1/amp-timeago.js
@@ -20,7 +20,7 @@ import {
   observeWithSharedInOb,
   unobserveWithSharedInOb,
 } from '../../../src/viewport-observer';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 export class AmpTimeAgo extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-timeago/1.0/amp-timeago.js b/extensions/amp-timeago/1.0/amp-timeago.js
index 37f726e80fa0..5262d21ee18d 100644
--- a/extensions/amp-timeago/1.0/amp-timeago.js
+++ b/extensions/amp-timeago/1.0/amp-timeago.js
@@ -16,7 +16,7 @@
 
 import {BaseElement} from './base-element';
 import {isExperimentOn} from '../../../src/experiments';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /** @const {string} */
 const TAG = 'amp-timeago';
diff --git a/extensions/amp-video/1.0/amp-video.js b/extensions/amp-video/1.0/amp-video.js
index 02a0b78ba7d9..292698890ba7 100644
--- a/extensions/amp-video/1.0/amp-video.js
+++ b/extensions/amp-video/1.0/amp-video.js
@@ -17,7 +17,7 @@
 import {CSS} from '../../../build/amp-video-1.0.css';
 import {VideoBaseElement} from './base-element';
 import {isExperimentOn} from '../../../src/experiments';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /** @const {string} */
 const TAG = 'amp-video';
diff --git a/extensions/amp-vimeo/0.1/amp-vimeo.js b/extensions/amp-vimeo/0.1/amp-vimeo.js
index 83bd4cde7740..47d04e101d12 100644
--- a/extensions/amp-vimeo/0.1/amp-vimeo.js
+++ b/extensions/amp-vimeo/0.1/amp-vimeo.js
@@ -32,7 +32,7 @@ import {getMode} from '../../../src/mode';
 import {installVideoManagerForDoc} from '../../../src/service/video-manager-impl';
 import {isLayoutSizeDefined} from '../../../src/layout';
 import {once} from '../../../src/utils/function';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 const TAG = 'amp-vimeo';
 
diff --git a/extensions/amp-vine/0.1/amp-vine.js b/extensions/amp-vine/0.1/amp-vine.js
index 95633d7056c9..3aa9cca4aae7 100644
--- a/extensions/amp-vine/0.1/amp-vine.js
+++ b/extensions/amp-vine/0.1/amp-vine.js
@@ -16,7 +16,7 @@
 
 import {Services} from '../../../src/services';
 import {isLayoutSizeDefined} from '../../../src/layout';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 class AmpVine extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-yotpo/0.1/amp-yotpo.js b/extensions/amp-yotpo/0.1/amp-yotpo.js
index 129861c19ac9..a516f4b150cc 100644
--- a/extensions/amp-yotpo/0.1/amp-yotpo.js
+++ b/extensions/amp-yotpo/0.1/amp-yotpo.js
@@ -19,7 +19,7 @@ import {getIframe} from '../../../src/3p-frame';
 import {isLayoutSizeDefined} from '../../../src/layout';
 import {listenFor} from '../../../src/iframe-helper';
 import {removeElement} from '../../../src/dom';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 export class AmpYotpo extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-youtube/1.0/amp-youtube.js b/extensions/amp-youtube/1.0/amp-youtube.js
index 283e0764b760..1617bca32e56 100644
--- a/extensions/amp-youtube/1.0/amp-youtube.js
+++ b/extensions/amp-youtube/1.0/amp-youtube.js
@@ -17,7 +17,7 @@
 import {BaseElement} from './base-element';
 import {CSS} from '../../../build/amp-youtube-1.0.css';
 import {isExperimentOn} from '../../../src/experiments';
-import {userAssert} from '../../../src/log';
+import {pureUserAssert as userAssert} from '../../../src/pure-assert';
 
 /** @const {string} */
 const TAG = 'amp-youtube';
diff --git a/src/cookies.js b/src/cookies.js
index bd4ea074654e..36b441c55243 100644
--- a/src/cookies.js
+++ b/src/cookies.js
@@ -22,7 +22,7 @@ import {
   tryDecodeUriComponent,
 } from './url';
 import {urls} from './config';
-import {userAssert} from './log';
+import {pureUserAssert as userAssert} from './pure-assert';
 
 const TEST_COOKIE_NAME = '-test-amp-cookie-tmp';
 
diff --git a/src/element-service.js b/src/element-service.js
index 47a40972fd8f..aa79a1761829 100644
--- a/src/element-service.js
+++ b/src/element-service.js
@@ -24,7 +24,7 @@ import {
   getServicePromiseOrNull,
   getServicePromiseOrNullForDoc,
 } from './service';
-import {userAssert} from './log';
+import {pureUserAssert as userAssert} from './pure-assert';
 
 /**
  * Returns a promise for a service for the given id and window. Also expects an
diff --git a/src/service/custom-element-registry.js b/src/service/custom-element-registry.js
index bf6b897346a9..43de2f2b9ef7 100644
--- a/src/service/custom-element-registry.js
+++ b/src/service/custom-element-registry.js
@@ -19,7 +19,7 @@ import {Services} from '../services';
 import {createCustomElementClass, stubbedElements} from '../custom-element';
 import {extensionScriptsInNode} from '../element-service';
 import {reportError} from '../error';
-import {userAssert} from '../log';
+import {pureUserAssert as userAssert} from '../pure-assert';
 
 /**
  * @param {!Window} win
diff --git a/src/service/template-impl.js b/src/service/template-impl.js
index a8dc2313cb88..dd19f77f1f92 100644
--- a/src/service/template-impl.js
+++ b/src/service/template-impl.js
@@ -17,7 +17,7 @@
 import {Deferred} from '../utils/promise';
 import {getService, registerServiceBuilder} from '../service';
 import {rootNodeFor, scopedQuerySelector} from '../dom';
-import {userAssert} from '../log';
+import {pureUserAssert as userAssert} from '../pure-assert';
 
 /**
  * @fileoverview
diff --git a/src/ssr-template-helper.js b/src/ssr-template-helper.js
index 1e9a1f63eb8f..5656f86bb6e7 100644
--- a/src/ssr-template-helper.js
+++ b/src/ssr-template-helper.js
@@ -17,7 +17,7 @@
 import {dict} from './utils/object';
 import {isArray} from './types';
 import {toStructuredCloneable} from './utils/xhr-utils';
-import {userAssert} from './log';
+import {pureUserAssert as userAssert} from './pure-assert';
 
 /**
  * @typedef {{
diff --git a/src/url.js b/src/url.js
index 6a84170e1d3b..4210325274a2 100644
--- a/src/url.js
+++ b/src/url.js
@@ -22,7 +22,7 @@ import {isArray} from './types';
 import {parseQueryString_} from './url-parse-query-string';
 import {tryDecodeUriComponent_} from './url-try-decode-uri-component';
 import {urls} from './config';
-import {userAssert} from './log';
+import {pureUserAssert as userAssert} from './pure-assert';
 
 /**
  * @type {!JsonObject}

From 520ccc4bce347b1cb0f8763a3713100b45ec79a6 Mon Sep 17 00:00:00 2001
From: Ryan Cebulko <ryan@cebulko.com>
Date: Tue, 23 Feb 2021 13:11:16 -0500
Subject: [PATCH 09/15] fix import path

---
 3p/facebook.js                                                  | 2 +-
 3p/github.js                                                    | 2 +-
 3p/mathml.js                                                    | 2 +-
 ads/vendors/csa.js                                              | 2 +-
 .../__component_version__/amp-__component_name_hyphenated__.js  | 2 +-
 contributing/building-a-bento-amp-extension.md                  | 2 +-
 contributing/building-an-amp-extension.md                       | 2 +-
 extensions/amp-a4a/0.1/amp-ad-template-helper.js                | 2 +-
 extensions/amp-a4a/0.1/friendly-frame-renderer.js               | 2 +-
 extensions/amp-a4a/0.1/template-renderer.js                     | 2 +-
 extensions/amp-access-scroll/0.1/scroll-component.js            | 2 +-
 extensions/amp-accordion/1.0/amp-accordion.js                   | 2 +-
 extensions/amp-action-macro/0.1/amp-action-macro.js             | 2 +-
 extensions/amp-ad-custom/0.1/amp-ad-custom.js                   | 2 +-
 extensions/amp-ad-exit/0.1/filters/click-location.js            | 2 +-
 .../amp-ad-network-adsense-impl/0.1/adsense-shared-state.js     | 2 +-
 .../0.1/test/test-doubleclick-sra.js                            | 2 +-
 extensions/amp-ad/0.1/amp-ad-custom.js                          | 2 +-
 extensions/amp-ad/0.1/amp-ad-ui.js                              | 2 +-
 extensions/amp-ad/0.1/amp-ad.js                                 | 2 +-
 extensions/amp-addthis/0.1/amp-addthis.js                       | 2 +-
 extensions/amp-analytics/0.1/scroll-manager.js                  | 2 +-
 extensions/amp-analytics/0.1/visibility-model.js                | 2 +-
 .../amp-animation/0.1/runners/native-web-animation-runner.js    | 2 +-
 extensions/amp-animation/0.1/runners/utils.js                   | 2 +-
 extensions/amp-auto-ads/0.1/amp-auto-ads.js                     | 2 +-
 extensions/amp-autocomplete/0.1/autocomplete-binding-inline.js  | 2 +-
 extensions/amp-base-carousel/1.0/amp-base-carousel.js           | 2 +-
 .../amp-bodymovin-animation/0.1/amp-bodymovin-animation.js      | 2 +-
 extensions/amp-carousel/0.1/base-slides.js                      | 2 +-
 extensions/amp-connatix-player/0.1/amp-connatix-player.js       | 2 +-
 extensions/amp-delight-player/0.1/amp-delight-player.js         | 2 +-
 extensions/amp-embedly-card/0.1/amp-embedly-card-impl.js        | 2 +-
 extensions/amp-embedly-card/0.1/amp-embedly-key.js              | 2 +-
 extensions/amp-experiment/1.0/mutation-record.js                | 2 +-
 extensions/amp-experiment/1.0/mutation/mutation.js              | 2 +-
 extensions/amp-fit-text/1.0/amp-fit-text.js                     | 2 +-
 .../amp-fx-collection/0.1/providers/amp-fx-presets-utils.js     | 2 +-
 extensions/amp-fx-collection/0.1/providers/fx-provider.js       | 2 +-
 extensions/amp-gwd-animation/0.1/amp-gwd-animation.js           | 2 +-
 extensions/amp-imgur/0.1/amp-imgur.js                           | 2 +-
 .../amp-inline-gallery/0.1/amp-inline-gallery-pagination.js     | 2 +-
 .../amp-inline-gallery/1.0/amp-inline-gallery-pagination.js     | 2 +-
 .../amp-inline-gallery/1.0/amp-inline-gallery-thumbnails.js     | 2 +-
 extensions/amp-inline-gallery/1.0/amp-inline-gallery.js         | 2 +-
 extensions/amp-inputmask/0.1/text-mask.js                       | 2 +-
 extensions/amp-instagram/0.1/amp-instagram.js                   | 2 +-
 extensions/amp-instagram/1.0/amp-instagram.js                   | 2 +-
 extensions/amp-kaltura-player/0.1/amp-kaltura-player.js         | 2 +-
 extensions/amp-lightbox-gallery/0.1/lightbox-controls.js        | 2 +-
 extensions/amp-lightbox/1.0/amp-lightbox.js                     | 2 +-
 extensions/amp-live-list/0.1/live-list-manager.js               | 2 +-
 extensions/amp-megaphone/0.1/amp-megaphone.js                   | 2 +-
 extensions/amp-next-page/1.0/page.js                            | 2 +-
 extensions/amp-next-page/1.0/visibility-observer.js             | 2 +-
 extensions/amp-o2-player/0.1/amp-o2-player.js                   | 2 +-
 .../amp-orientation-observer/0.1/amp-orientation-observer.js    | 2 +-
 extensions/amp-pinterest/0.1/follow-button.js                   | 2 +-
 extensions/amp-recaptcha-input/0.1/amp-recaptcha-input.js       | 2 +-
 extensions/amp-redbull-player/0.1/amp-redbull-player.js         | 2 +-
 extensions/amp-reddit/0.1/amp-reddit.js                         | 2 +-
 extensions/amp-riddle-quiz/0.1/amp-riddle-quiz.js               | 2 +-
 extensions/amp-selector/1.0/amp-selector.js                     | 2 +-
 extensions/amp-sidebar/1.0/amp-sidebar.js                       | 2 +-
 extensions/amp-skimlinks/0.1/link-rewriter/link-rewriter.js     | 2 +-
 extensions/amp-skimlinks/0.1/skim-options.js                    | 2 +-
 extensions/amp-social-share/1.0/amp-social-share.js             | 2 +-
 extensions/amp-soundcloud/0.1/amp-soundcloud.js                 | 2 +-
 extensions/amp-springboard-player/0.1/amp-springboard-player.js | 2 +-
 .../amp-story-auto-analytics/0.1/amp-story-auto-analytics.js    | 2 +-
 extensions/amp-story/1.0/animation-presets.js                   | 2 +-
 extensions/amp-story/1.0/bookend/components/article.js          | 2 +-
 extensions/amp-story/1.0/bookend/components/cta-link.js         | 2 +-
 extensions/amp-story/1.0/bookend/components/heading.js          | 2 +-
 extensions/amp-story/1.0/bookend/components/landscape.js        | 2 +-
 extensions/amp-story/1.0/bookend/components/portrait.js         | 2 +-
 extensions/amp-story/1.0/bookend/components/text-box.js         | 2 +-
 extensions/amp-story/1.0/live-story-manager.js                  | 2 +-
 extensions/amp-story/1.0/pagination-buttons.js                  | 2 +-
 extensions/amp-story/1.0/simple-template.js                     | 2 +-
 extensions/amp-stream-gallery/1.0/amp-stream-gallery.js         | 2 +-
 extensions/amp-timeago/0.1/amp-timeago.js                       | 2 +-
 extensions/amp-timeago/1.0/amp-timeago.js                       | 2 +-
 extensions/amp-truncate-text/0.1/binary-search.js               | 2 +-
 extensions/amp-video/1.0/amp-video.js                           | 2 +-
 extensions/amp-viewer-integration/0.1/findtext.js               | 2 +-
 extensions/amp-vimeo/0.1/amp-vimeo.js                           | 2 +-
 extensions/amp-vine/0.1/amp-vine.js                             | 2 +-
 extensions/amp-yotpo/0.1/amp-yotpo.js                           | 2 +-
 extensions/amp-youtube/1.0/amp-youtube.js                       | 2 +-
 src/action-constants.js                                         | 2 +-
 src/context/component-hooks.js                                  | 2 +-
 src/context/node.js                                             | 2 +-
 src/context/prop.js                                             | 2 +-
 src/cookies.js                                                  | 2 +-
 src/css.js                                                      | 2 +-
 src/element-service.js                                          | 2 +-
 src/extension-analytics.js                                      | 2 +-
 src/finite-state-machine.js                                     | 2 +-
 src/gesture.js                                                  | 2 +-
 src/modal.js                                                    | 2 +-
 src/preact/base-element.js                                      | 2 +-
 src/render-delaying-services.js                                 | 2 +-
 src/service/core-services.js                                    | 2 +-
 src/service/custom-element-registry.js                          | 2 +-
 src/service/hidden-observer-impl.js                             | 2 +-
 src/service/owners-impl.js                                      | 2 +-
 src/service/position-observer/position-observer-worker.js       | 2 +-
 src/service/task-queue.js                                       | 2 +-
 src/service/template-impl.js                                    | 2 +-
 src/service/variable-source.js                                  | 2 +-
 src/ssr-template-helper.js                                      | 2 +-
 src/static-template.js                                          | 2 +-
 src/url.js                                                      | 2 +-
 src/utils/bytes.js                                              | 2 +-
 src/utils/detached-dom-stream.js                                | 2 +-
 src/utils/math.js                                               | 2 +-
 src/viewport-observer.js                                        | 2 +-
 118 files changed, 118 insertions(+), 118 deletions(-)

diff --git a/3p/facebook.js b/3p/facebook.js
index 5afe609195bc..0590f15e693e 100644
--- a/3p/facebook.js
+++ b/3p/facebook.js
@@ -18,7 +18,7 @@ import {dashToUnderline} from '../src/string';
 import {dict} from '../src/utils/object';
 import {loadScript} from './3p';
 import {setStyle} from '../src/style';
-import {pureUserAssert as userAssert} from '../src/pure-assert';
+import {pureUserAssert as userAssert} from '../src/assert';
 
 /**
  * Produces the Facebook SDK object for the passed in callback.
diff --git a/3p/github.js b/3p/github.js
index 04931b887248..7b697106be88 100644
--- a/3p/github.js
+++ b/3p/github.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {pureUserAssert as userAssert} from '../src/pure-assert';
+import {pureUserAssert as userAssert} from '../src/assert';
 import {writeScript} from './3p';
 
 /**
diff --git a/3p/mathml.js b/3p/mathml.js
index 3792aab27062..23de90f355e1 100644
--- a/3p/mathml.js
+++ b/3p/mathml.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 import {setStyle} from '../src/style';
-import {pureUserAssert as userAssert} from '../src/pure-assert';
+import {pureUserAssert as userAssert} from '../src/assert';
 import {writeScript} from './3p';
 
 /**
diff --git a/ads/vendors/csa.js b/ads/vendors/csa.js
index d91bf42b0f70..3e9bb767219e 100644
--- a/ads/vendors/csa.js
+++ b/ads/vendors/csa.js
@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-import {pureDevAssert as devAssert} from '../../src/pure-assert';
+import {pureDevAssert as devAssert} from '../../src/assert';
 import {getStyle, setStyle, setStyles} from '../../src/style';
 import {loadScript, validateData} from '../../3p/3p';
 import {tryParseJson} from '../../src/json.js';
diff --git a/build-system/tasks/extension-generator/bento/amp-__component_name_hyphenated__/__component_version__/amp-__component_name_hyphenated__.js b/build-system/tasks/extension-generator/bento/amp-__component_name_hyphenated__/__component_version__/amp-__component_name_hyphenated__.js
index ed83d640a334..920ad6f2cfc1 100644
--- a/build-system/tasks/extension-generator/bento/amp-__component_name_hyphenated__/__component_version__/amp-__component_name_hyphenated__.js
+++ b/build-system/tasks/extension-generator/bento/amp-__component_name_hyphenated__/__component_version__/amp-__component_name_hyphenated__.js
@@ -18,7 +18,7 @@ import {BaseElement} from './base-element';
 import {CSS} from '../../../build/amp-__component_name_hyphenated__-__component_version__.css';
 import {dict} from '../../../src/utils/object';
 import {isExperimentOn} from '../../../src/experiments';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /** @const {string} */
 const TAG = 'amp-__component_name_hyphenated__';
diff --git a/contributing/building-a-bento-amp-extension.md b/contributing/building-a-bento-amp-extension.md
index 6bcded1259f5..bcd9a8eea92e 100644
--- a/contributing/building-a-bento-amp-extension.md
+++ b/contributing/building-a-bento-amp-extension.md
@@ -484,7 +484,7 @@ Then protect your code with a check for the component-specific flag `isExperimen
 ```javascript
 import {CSS} from '../../../build/amp-my-element-0.1.css';
 import {isExperimentOn} from '../../../src/experiments';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /** @const */
 const TAG = 'amp-my-element';
diff --git a/contributing/building-an-amp-extension.md b/contributing/building-an-amp-extension.md
index 1e0c10c66f29..47d5141aee5a 100644
--- a/contributing/building-an-amp-extension.md
+++ b/contributing/building-an-amp-extension.md
@@ -659,7 +659,7 @@ And then protecting your code with a check `isExperimentOn(win, 'amp-my-element'
 
 ```javascript
 import {isExperimentOn} from '../../../src/experiments';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /** @const */
 const EXPERIMENT = 'amp-my-element';
diff --git a/extensions/amp-a4a/0.1/amp-ad-template-helper.js b/extensions/amp-a4a/0.1/amp-ad-template-helper.js
index 4e9fe863d01c..ed3709b728e6 100644
--- a/extensions/amp-a4a/0.1/amp-ad-template-helper.js
+++ b/extensions/amp-a4a/0.1/amp-ad-template-helper.js
@@ -17,7 +17,7 @@
 import {LruCache} from '../../../src/utils/lru-cache';
 import {Services} from '../../../src/services';
 import {createElementWithAttributes} from '../../../src/dom';
-import {pureDevAssert as devAssert} from '../../../src/pure-assert';
+import {pureDevAssert as devAssert} from '../../../src/assert';
 import {dict} from '../../../src/utils/object';
 import {getMode} from '../../../src/mode';
 import {isArray} from '../../../src/types';
diff --git a/extensions/amp-a4a/0.1/friendly-frame-renderer.js b/extensions/amp-a4a/0.1/friendly-frame-renderer.js
index 1dfdcadc6fb5..feeb893598de 100644
--- a/extensions/amp-a4a/0.1/friendly-frame-renderer.js
+++ b/extensions/amp-a4a/0.1/friendly-frame-renderer.js
@@ -15,7 +15,7 @@
  */
 
 import {Renderer} from './amp-ad-type-defs';
-import {pureDevAssert as devAssert} from '../../../src/pure-assert';
+import {pureDevAssert as devAssert} from '../../../src/assert';
 import {renderCreativeIntoFriendlyFrame} from './friendly-frame-util';
 
 /**
diff --git a/extensions/amp-a4a/0.1/template-renderer.js b/extensions/amp-a4a/0.1/template-renderer.js
index 27a09d692b14..16fae91a075a 100644
--- a/extensions/amp-a4a/0.1/template-renderer.js
+++ b/extensions/amp-a4a/0.1/template-renderer.js
@@ -15,7 +15,7 @@
  */
 
 import {Renderer} from './amp-ad-type-defs';
-import {devAssert} from '../../../src/assert';
+import {puredevAssert as devAssert} from '../../../src/assert';
 import {getAmpAdTemplateHelper} from './template-validator';
 import {renderCreativeIntoFriendlyFrame} from './friendly-frame-util';
 
diff --git a/extensions/amp-access-scroll/0.1/scroll-component.js b/extensions/amp-access-scroll/0.1/scroll-component.js
index dbbe6e8b4695..e3f26e4a269a 100644
--- a/extensions/amp-access-scroll/0.1/scroll-component.js
+++ b/extensions/amp-access-scroll/0.1/scroll-component.js
@@ -17,7 +17,7 @@
 import {Services} from '../../../src/services';
 import {assertDoesNotContainDisplay, px, setStyles} from '../../../src/style';
 import {createElementWithAttributes} from '../../../src/dom';
-import {pureDevAssert as devAssert} from '../../../src/pure-assert';
+import {pureDevAssert as devAssert} from '../../../src/assert';
 import {hasOwn} from '../../../src/utils/object';
 
 /** @abstract */
diff --git a/extensions/amp-accordion/1.0/amp-accordion.js b/extensions/amp-accordion/1.0/amp-accordion.js
index 2a579bb7c428..db3a75cce999 100644
--- a/extensions/amp-accordion/1.0/amp-accordion.js
+++ b/extensions/amp-accordion/1.0/amp-accordion.js
@@ -21,7 +21,7 @@ import {Services} from '../../../src/services';
 import {createCustomEvent} from '../../../src/event-helper';
 import {isExperimentOn} from '../../../src/experiments';
 import {toWin} from '../../../src/types';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /** @const {string} */
 const TAG = 'amp-accordion';
diff --git a/extensions/amp-action-macro/0.1/amp-action-macro.js b/extensions/amp-action-macro/0.1/amp-action-macro.js
index 5870f88a2ae7..bc8a4427dcbd 100644
--- a/extensions/amp-action-macro/0.1/amp-action-macro.js
+++ b/extensions/amp-action-macro/0.1/amp-action-macro.js
@@ -15,7 +15,7 @@
  */
 import {LayoutPriority} from '../../../src/layout';
 import {Services} from '../../../src/services';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /** @const {string} */
 const TAG = 'amp-action-macro';
diff --git a/extensions/amp-ad-custom/0.1/amp-ad-custom.js b/extensions/amp-ad-custom/0.1/amp-ad-custom.js
index 09a76ce9fcf3..77a0086d4b85 100644
--- a/extensions/amp-ad-custom/0.1/amp-ad-custom.js
+++ b/extensions/amp-ad-custom/0.1/amp-ad-custom.js
@@ -24,7 +24,7 @@ import {Services} from '../../../src/services';
 import {TemplateRenderer} from '../../amp-a4a/0.1/template-renderer';
 import {TemplateValidator} from '../../amp-a4a/0.1/template-validator';
 import {addParamToUrl} from '../../../src/url';
-import {pureDevAssert as devAssert} from '../../../src/pure-assert';
+import {pureDevAssert as devAssert} from '../../../src/assert';
 
 // These have no side-effects, and so may be reused between all instances.
 const validator = new TemplateValidator();
diff --git a/extensions/amp-ad-exit/0.1/filters/click-location.js b/extensions/amp-ad-exit/0.1/filters/click-location.js
index 2ba5c31a7ebf..3132d1807337 100644
--- a/extensions/amp-ad-exit/0.1/filters/click-location.js
+++ b/extensions/amp-ad-exit/0.1/filters/click-location.js
@@ -15,7 +15,7 @@
  */
 
 import {Filter, FilterType} from './filter';
-import {pureUserAssert as userAssert} from '../../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../../src/assert';
 
 export class ClickLocationFilter extends Filter {
   /**
diff --git a/extensions/amp-ad-network-adsense-impl/0.1/adsense-shared-state.js b/extensions/amp-ad-network-adsense-impl/0.1/adsense-shared-state.js
index c83a14afe657..b38cd1da06e7 100644
--- a/extensions/amp-ad-network-adsense-impl/0.1/adsense-shared-state.js
+++ b/extensions/amp-ad-network-adsense-impl/0.1/adsense-shared-state.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {pureDevAssert as devAssert} from '../../../src/pure-assert';
+import {pureDevAssert as devAssert} from '../../../src/assert';
 
 /**
  * Maintains state in between different AdSense slots on the same page. This
diff --git a/extensions/amp-ad-network-doubleclick-impl/0.1/test/test-doubleclick-sra.js b/extensions/amp-ad-network-doubleclick-impl/0.1/test/test-doubleclick-sra.js
index fa50a90c1558..0c796bb776c1 100644
--- a/extensions/amp-ad-network-doubleclick-impl/0.1/test/test-doubleclick-sra.js
+++ b/extensions/amp-ad-network-doubleclick-impl/0.1/test/test-doubleclick-sra.js
@@ -50,7 +50,7 @@ import {
 } from '../sra-utils';
 import {Xhr} from '../../../../src/service/xhr-impl';
 import {createElementWithAttributes} from '../../../../src/dom';
-import {pureDevAssert as devAssert} from '../../../../src/pure-assert';
+import {pureDevAssert as devAssert} from '../../../../src/assert';
 import {layoutRectLtwh} from '../../../../src/layout-rect';
 import {utf8Decode, utf8Encode} from '../../../../src/utils/bytes';
 
diff --git a/extensions/amp-ad/0.1/amp-ad-custom.js b/extensions/amp-ad/0.1/amp-ad-custom.js
index b5dd6441bcf8..82901e99cd83 100644
--- a/extensions/amp-ad/0.1/amp-ad-custom.js
+++ b/extensions/amp-ad/0.1/amp-ad-custom.js
@@ -25,7 +25,7 @@ import {
   removeChildren,
 } from '../../../src/dom';
 import {hasOwn} from '../../../src/utils/object';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /** @const {string} Tag name for custom ad implementation. */
 export const TAG_AD_CUSTOM = 'amp-ad-custom';
diff --git a/extensions/amp-ad/0.1/amp-ad-ui.js b/extensions/amp-ad/0.1/amp-ad-ui.js
index 9626e0eb7246..6b264171896e 100644
--- a/extensions/amp-ad/0.1/amp-ad-ui.js
+++ b/extensions/amp-ad/0.1/amp-ad-ui.js
@@ -24,7 +24,7 @@ import {
   createElementWithAttributes,
   removeElement,
 } from '../../../src/dom';
-import {pureDevAssert as devAssert} from '../../../src/pure-assert';
+import {pureDevAssert as devAssert} from '../../../src/assert';
 import {dict} from '../../../src/utils/object';
 import {getExperimentBranch} from '../../../src/experiments';
 
diff --git a/extensions/amp-ad/0.1/amp-ad.js b/extensions/amp-ad/0.1/amp-ad.js
index 690930858c40..2c52e3a25433 100644
--- a/extensions/amp-ad/0.1/amp-ad.js
+++ b/extensions/amp-ad/0.1/amp-ad.js
@@ -20,7 +20,7 @@ import {Services} from '../../../src/services';
 import {adConfig} from '../../../ads/_config';
 import {getA4ARegistry} from '../../../ads/_a4a-config';
 import {hasOwn} from '../../../src/utils/object';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /**
  * Construct ad network type-specific tag and script name.  Note that this
diff --git a/extensions/amp-addthis/0.1/amp-addthis.js b/extensions/amp-addthis/0.1/amp-addthis.js
index 364df95ab3b8..717da8fd3291 100644
--- a/extensions/amp-addthis/0.1/amp-addthis.js
+++ b/extensions/amp-addthis/0.1/amp-addthis.js
@@ -70,7 +70,7 @@ import {isLayoutSizeDefined} from '../../../src/layout';
 import {listen} from '../../../src/event-helper';
 import {parseUrlDeprecated} from '../../../src/url';
 import {setStyle} from '../../../src/style';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 // The following items will be shared by all AmpAddThis elements on a page, to
 // prevent unnecessary HTTP requests, get accurate analytics, etc., and hence
diff --git a/extensions/amp-analytics/0.1/scroll-manager.js b/extensions/amp-analytics/0.1/scroll-manager.js
index 32184519736c..92e7100ab850 100644
--- a/extensions/amp-analytics/0.1/scroll-manager.js
+++ b/extensions/amp-analytics/0.1/scroll-manager.js
@@ -16,7 +16,7 @@
 
 import {Observable} from '../../../src/observable';
 import {Services} from '../../../src/services';
-import {pureDevAssert as devAssert} from '../../../src/pure-assert';
+import {pureDevAssert as devAssert} from '../../../src/assert';
 
 /**
  * @typedef {{
diff --git a/extensions/amp-analytics/0.1/visibility-model.js b/extensions/amp-analytics/0.1/visibility-model.js
index 825b3c2b916e..e038b40fb23b 100644
--- a/extensions/amp-analytics/0.1/visibility-model.js
+++ b/extensions/amp-analytics/0.1/visibility-model.js
@@ -16,7 +16,7 @@
 
 import {Deferred} from '../../../src/utils/promise';
 import {Observable} from '../../../src/observable';
-import {pureDevAssert as devAssert} from '../../../src/pure-assert';
+import {pureDevAssert as devAssert} from '../../../src/assert';
 import {dict} from '../../../src/utils/object';
 
 /**
diff --git a/extensions/amp-animation/0.1/runners/native-web-animation-runner.js b/extensions/amp-animation/0.1/runners/native-web-animation-runner.js
index 5ff363495599..e0172d33bd97 100644
--- a/extensions/amp-animation/0.1/runners/native-web-animation-runner.js
+++ b/extensions/amp-animation/0.1/runners/native-web-animation-runner.js
@@ -29,7 +29,7 @@ import {
   WebSwitchAnimationDef,
 } from '../web-animation-types';
 import {assertDoesNotContainDisplay, setStyles} from '../../../../src/style';
-import {pureDevAssert as devAssert} from '../../../../src/pure-assert';
+import {pureDevAssert as devAssert} from '../../../../src/assert';
 import {getTotalDuration} from './utils';
 
 /**
diff --git a/extensions/amp-animation/0.1/runners/utils.js b/extensions/amp-animation/0.1/runners/utils.js
index c618b3b50de3..18cbf914429b 100644
--- a/extensions/amp-animation/0.1/runners/utils.js
+++ b/extensions/amp-animation/0.1/runners/utils.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {pureUserAssert as userAssert} from '../../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../../src/assert';
 
 /**
  * @param {!Array<!../web-animation-types.InternalWebAnimationRequestDef>} requests
diff --git a/extensions/amp-auto-ads/0.1/amp-auto-ads.js b/extensions/amp-auto-ads/0.1/amp-auto-ads.js
index cc4c7ac035dd..9f0f14e646a7 100644
--- a/extensions/amp-auto-ads/0.1/amp-auto-ads.js
+++ b/extensions/amp-auto-ads/0.1/amp-auto-ads.js
@@ -27,7 +27,7 @@ import {dict} from '../../../src/utils/object';
 import {getAdNetworkConfig} from './ad-network-config';
 import {getPlacementsFromConfigObj} from './placement';
 import {isExperimentOn} from '../../../src/experiments';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /** @const */
 const TAG = 'amp-auto-ads';
diff --git a/extensions/amp-autocomplete/0.1/autocomplete-binding-inline.js b/extensions/amp-autocomplete/0.1/autocomplete-binding-inline.js
index 7626eb3fd91e..2dd8689f8d75 100644
--- a/extensions/amp-autocomplete/0.1/autocomplete-binding-inline.js
+++ b/extensions/amp-autocomplete/0.1/autocomplete-binding-inline.js
@@ -16,7 +16,7 @@
 
 import {ownProperty} from '../../../src/utils/object';
 import {tryFocus} from '../../../src/dom';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 const TAG = 'amp-autocomplete';
 
diff --git a/extensions/amp-base-carousel/1.0/amp-base-carousel.js b/extensions/amp-base-carousel/1.0/amp-base-carousel.js
index d58c28587afc..3799c865d785 100644
--- a/extensions/amp-base-carousel/1.0/amp-base-carousel.js
+++ b/extensions/amp-base-carousel/1.0/amp-base-carousel.js
@@ -25,7 +25,7 @@ import {createCustomEvent} from '../../../src/event-helper';
 import {dict} from '../../../src/utils/object';
 import {dispatchCustomEvent} from '../../../src/dom';
 import {isExperimentOn} from '../../../src/experiments';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /** @const {string} */
 const TAG = 'amp-base-carousel';
diff --git a/extensions/amp-bodymovin-animation/0.1/amp-bodymovin-animation.js b/extensions/amp-bodymovin-animation/0.1/amp-bodymovin-animation.js
index 212dbd66a35b..6b185409504e 100644
--- a/extensions/amp-bodymovin-animation/0.1/amp-bodymovin-animation.js
+++ b/extensions/amp-bodymovin-animation/0.1/amp-bodymovin-animation.js
@@ -27,7 +27,7 @@ import {isFiniteNumber, isObject} from '../../../src/types';
 import {isLayoutSizeDefined} from '../../../src/layout';
 import {parseJson} from '../../../src/json';
 import {removeElement} from '../../../src/dom';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 const TAG = 'amp-bodymovin-animation';
 
diff --git a/extensions/amp-carousel/0.1/base-slides.js b/extensions/amp-carousel/0.1/base-slides.js
index 83883b56ebc2..f310eb041cbc 100644
--- a/extensions/amp-carousel/0.1/base-slides.js
+++ b/extensions/amp-carousel/0.1/base-slides.js
@@ -18,7 +18,7 @@ import {ActionTrust} from '../../../src/action-constants';
 import {BaseCarousel} from './base-carousel';
 import {Services} from '../../../src/services';
 import {isFiniteNumber} from '../../../src/types';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 export class BaseSlides extends BaseCarousel {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-connatix-player/0.1/amp-connatix-player.js b/extensions/amp-connatix-player/0.1/amp-connatix-player.js
index c41fe83bed37..dd0347df1240 100644
--- a/extensions/amp-connatix-player/0.1/amp-connatix-player.js
+++ b/extensions/amp-connatix-player/0.1/amp-connatix-player.js
@@ -37,7 +37,7 @@ import {
 import {removeElement} from '../../../src/dom';
 import {setIsMediaComponent} from '../../../src/video-interface';
 import {tryParseJson} from '../../../src/json';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /**
  * @param {!Array<T>} promises
diff --git a/extensions/amp-delight-player/0.1/amp-delight-player.js b/extensions/amp-delight-player/0.1/amp-delight-player.js
index 1e16a91529be..f1ce7d0eafd2 100644
--- a/extensions/amp-delight-player/0.1/amp-delight-player.js
+++ b/extensions/amp-delight-player/0.1/amp-delight-player.js
@@ -40,7 +40,7 @@ import {
   unobserveWithSharedInOb,
 } from '../../../src/viewport-observer';
 import {setStyle} from '../../../src/style';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /** @const */
 const TAG = 'amp-delight-player';
diff --git a/extensions/amp-embedly-card/0.1/amp-embedly-card-impl.js b/extensions/amp-embedly-card/0.1/amp-embedly-card-impl.js
index ebe9525a2872..4c447fe2a57d 100644
--- a/extensions/amp-embedly-card/0.1/amp-embedly-card-impl.js
+++ b/extensions/amp-embedly-card/0.1/amp-embedly-card-impl.js
@@ -20,7 +20,7 @@ import {Services} from '../../../src/services';
 import {getIframe} from '../../../src/3p-frame';
 import {listenFor} from '../../../src/iframe-helper';
 import {removeElement} from '../../../src/dom';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /**
  * Component tag identifier.
diff --git a/extensions/amp-embedly-card/0.1/amp-embedly-key.js b/extensions/amp-embedly-card/0.1/amp-embedly-key.js
index 793d4847d674..b043ab7c4eba 100644
--- a/extensions/amp-embedly-card/0.1/amp-embedly-key.js
+++ b/extensions/amp-embedly-card/0.1/amp-embedly-key.js
@@ -15,7 +15,7 @@
  */
 
 import {Layout} from '../../../src/layout';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /** @const {string} */
 export const TAG = 'amp-embedly-key';
diff --git a/extensions/amp-experiment/1.0/mutation-record.js b/extensions/amp-experiment/1.0/mutation-record.js
index 268f3a84f484..a86add188e46 100644
--- a/extensions/amp-experiment/1.0/mutation-record.js
+++ b/extensions/amp-experiment/1.0/mutation-record.js
@@ -15,7 +15,7 @@
  */
 
 import {isObject, toArray} from '../../../src/types';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /**
  * Types of possibile mutations
diff --git a/extensions/amp-experiment/1.0/mutation/mutation.js b/extensions/amp-experiment/1.0/mutation/mutation.js
index fa892ef7eff0..48f23ce298b1 100644
--- a/extensions/amp-experiment/1.0/mutation/mutation.js
+++ b/extensions/amp-experiment/1.0/mutation/mutation.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {pureUserAssert as userAssert} from '../../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../../src/assert';
 
 /**
  * Interface for amp-experiment mutations.
diff --git a/extensions/amp-fit-text/1.0/amp-fit-text.js b/extensions/amp-fit-text/1.0/amp-fit-text.js
index ac110d077c4e..cec470bd08cc 100644
--- a/extensions/amp-fit-text/1.0/amp-fit-text.js
+++ b/extensions/amp-fit-text/1.0/amp-fit-text.js
@@ -17,7 +17,7 @@
 import {BaseElement} from './base-element';
 import {CSS} from '../../../build/amp-fit-text-1.0.css';
 import {isExperimentOn} from '../../../src/experiments';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /** @const {string} */
 const TAG = 'amp-fit-text';
diff --git a/extensions/amp-fx-collection/0.1/providers/amp-fx-presets-utils.js b/extensions/amp-fx-collection/0.1/providers/amp-fx-presets-utils.js
index 00630de3bf0a..025038b83dda 100644
--- a/extensions/amp-fx-collection/0.1/providers/amp-fx-presets-utils.js
+++ b/extensions/amp-fx-collection/0.1/providers/amp-fx-presets-utils.js
@@ -22,7 +22,7 @@
 import {FxType} from '../fx-type';
 import {Services} from '../../../../src/services';
 import {mapRange} from '../../../../src/utils/math';
-import {pureUserAssert as userAssert} from '../../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../../src/assert';
 
 const MAX_MOBILE_WIDTH = 480;
 const MAX_TABLET_WIDTH = 1000;
diff --git a/extensions/amp-fx-collection/0.1/providers/fx-provider.js b/extensions/amp-fx-collection/0.1/providers/fx-provider.js
index da350ffb6699..a009d1d9a934 100644
--- a/extensions/amp-fx-collection/0.1/providers/fx-provider.js
+++ b/extensions/amp-fx-collection/0.1/providers/fx-provider.js
@@ -41,7 +41,7 @@ import {
   installStyles,
   resolvePercentageToNumber,
 } from './amp-fx-presets-utils';
-import {pureDevAssert as devAssert} from '../../../../src/pure-assert';
+import {pureDevAssert as devAssert} from '../../../../src/assert';
 import {
   getServiceForDoc,
   registerServiceBuilderForDoc,
diff --git a/extensions/amp-gwd-animation/0.1/amp-gwd-animation.js b/extensions/amp-gwd-animation/0.1/amp-gwd-animation.js
index 12d6b45840bd..5faf41ba72e0 100644
--- a/extensions/amp-gwd-animation/0.1/amp-gwd-animation.js
+++ b/extensions/amp-gwd-animation/0.1/amp-gwd-animation.js
@@ -27,7 +27,7 @@ import {
   getParentWindowFrameElement,
   getServiceForDocOrNull,
 } from '../../../src/service';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /**
  * Returns a value at any level in an object structure addressed by dot-notation
diff --git a/extensions/amp-imgur/0.1/amp-imgur.js b/extensions/amp-imgur/0.1/amp-imgur.js
index 5c42f478f425..e685df5d52b7 100644
--- a/extensions/amp-imgur/0.1/amp-imgur.js
+++ b/extensions/amp-imgur/0.1/amp-imgur.js
@@ -32,7 +32,7 @@ import {isLayoutSizeDefined} from '../../../src/layout';
 import {isObject} from '../../../src/types';
 import {removeElement} from '../../../src/dom';
 import {tryParseJson} from '../../../src/json';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 export class AmpImgur extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-inline-gallery/0.1/amp-inline-gallery-pagination.js b/extensions/amp-inline-gallery/0.1/amp-inline-gallery-pagination.js
index a292406864b9..7823b44964ea 100644
--- a/extensions/amp-inline-gallery/0.1/amp-inline-gallery-pagination.js
+++ b/extensions/amp-inline-gallery/0.1/amp-inline-gallery-pagination.js
@@ -17,7 +17,7 @@
 import {InlineGalleryEvents} from './inline-gallery-events';
 import {Layout} from '../../../src/layout';
 import {createCustomEvent} from '../../../src/event-helper';
-import {pureDevAssert as devAssert} from '../../../src/pure-assert';
+import {pureDevAssert as devAssert} from '../../../src/assert';
 import {dict} from '../../../src/utils/object';
 import {htmlFor} from '../../../src/static-template';
 import {scopedQuerySelectorAll} from '../../../src/dom';
diff --git a/extensions/amp-inline-gallery/1.0/amp-inline-gallery-pagination.js b/extensions/amp-inline-gallery/1.0/amp-inline-gallery-pagination.js
index 78b197212043..d9ca19665fdd 100644
--- a/extensions/amp-inline-gallery/1.0/amp-inline-gallery-pagination.js
+++ b/extensions/amp-inline-gallery/1.0/amp-inline-gallery-pagination.js
@@ -19,7 +19,7 @@ import {CarouselContextProp} from '../../amp-base-carousel/1.0/carousel-props';
 import {Pagination} from './pagination';
 import {PreactBaseElement} from '../../../src/preact/base-element';
 import {isExperimentOn} from '../../../src/experiments';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /** @const {string} */
 export const TAG = 'amp-inline-gallery-pagination';
diff --git a/extensions/amp-inline-gallery/1.0/amp-inline-gallery-thumbnails.js b/extensions/amp-inline-gallery/1.0/amp-inline-gallery-thumbnails.js
index c1754602ca37..863fbda4201e 100644
--- a/extensions/amp-inline-gallery/1.0/amp-inline-gallery-thumbnails.js
+++ b/extensions/amp-inline-gallery/1.0/amp-inline-gallery-thumbnails.js
@@ -20,7 +20,7 @@ import {PreactBaseElement} from '../../../src/preact/base-element';
 import {CSS as THUMBNAIL_CSS} from './thumbnails.jss';
 import {Thumbnails} from './thumbnails';
 import {isExperimentOn} from '../../../src/experiments';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /** @const {string} */
 export const TAG = 'amp-inline-gallery-thumbnails';
diff --git a/extensions/amp-inline-gallery/1.0/amp-inline-gallery.js b/extensions/amp-inline-gallery/1.0/amp-inline-gallery.js
index e79322e829f9..cf0368f1d5ea 100644
--- a/extensions/amp-inline-gallery/1.0/amp-inline-gallery.js
+++ b/extensions/amp-inline-gallery/1.0/amp-inline-gallery.js
@@ -32,7 +32,7 @@ import {dict} from '../../../src/utils/object';
 import {isExperimentOn} from '../../../src/experiments';
 import {setProp} from '../../../src/context';
 import {useContext, useLayoutEffect} from '../../../src/preact';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /** @const {string} */
 const TAG = 'amp-inline-gallery';
diff --git a/extensions/amp-inputmask/0.1/text-mask.js b/extensions/amp-inputmask/0.1/text-mask.js
index 889c32cb9ae0..c9d72fb1712c 100644
--- a/extensions/amp-inputmask/0.1/text-mask.js
+++ b/extensions/amp-inputmask/0.1/text-mask.js
@@ -18,7 +18,7 @@ import {Mask} from './mask-impl';
 import {OutputMode} from './constants';
 import {Services} from '../../../src/services';
 import {iterateCursor, removeElement} from '../../../src/dom';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 const ELEMENT_MASK_PROPERTY = '__amp_inputmask_masked';
 const ELEMENT_MASK_OUTPUT_PROPERTY = '__amp_inputmask_hidden';
diff --git a/extensions/amp-instagram/0.1/amp-instagram.js b/extensions/amp-instagram/0.1/amp-instagram.js
index 849d939a50ea..5b8b19fc2c0a 100644
--- a/extensions/amp-instagram/0.1/amp-instagram.js
+++ b/extensions/amp-instagram/0.1/amp-instagram.js
@@ -43,7 +43,7 @@ import {isObject} from '../../../src/types';
 import {removeElement} from '../../../src/dom';
 import {setStyle} from '../../../src/style';
 import {tryParseJson} from '../../../src/json';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 export class AmpInstagram extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-instagram/1.0/amp-instagram.js b/extensions/amp-instagram/1.0/amp-instagram.js
index 1346557662ac..c14fa53c880b 100644
--- a/extensions/amp-instagram/1.0/amp-instagram.js
+++ b/extensions/amp-instagram/1.0/amp-instagram.js
@@ -18,7 +18,7 @@ import {BaseElement} from './base-element';
 import {CSS} from '../../../build/amp-instagram-1.0.css';
 import {dict} from '../../../src/utils/object';
 import {isExperimentOn} from '../../../src/experiments';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /** @const {string} */
 const TAG = 'amp-instagram';
diff --git a/extensions/amp-kaltura-player/0.1/amp-kaltura-player.js b/extensions/amp-kaltura-player/0.1/amp-kaltura-player.js
index fc55a181745d..b34d28716654 100644
--- a/extensions/amp-kaltura-player/0.1/amp-kaltura-player.js
+++ b/extensions/amp-kaltura-player/0.1/amp-kaltura-player.js
@@ -20,7 +20,7 @@ import {dict} from '../../../src/utils/object';
 import {getDataParamsFromAttributes} from '../../../src/dom';
 import {isLayoutSizeDefined} from '../../../src/layout';
 import {setIsMediaComponent} from '../../../src/video-interface';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 class AmpKaltura extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-lightbox-gallery/0.1/lightbox-controls.js b/extensions/amp-lightbox-gallery/0.1/lightbox-controls.js
index 68e203c6c030..12ba4354fedf 100644
--- a/extensions/amp-lightbox-gallery/0.1/lightbox-controls.js
+++ b/extensions/amp-lightbox-gallery/0.1/lightbox-controls.js
@@ -16,7 +16,7 @@
 
 import {Services} from '../../../src/services';
 import {createCustomEvent} from '../../../src/event-helper';
-import {pureDevAssert as devAssert} from '../../../src/pure-assert';
+import {pureDevAssert as devAssert} from '../../../src/assert';
 import {dict} from '../../../src/utils/object';
 import {htmlFor} from '../../../src/static-template';
 import {toArray} from '../../../src/types';
diff --git a/extensions/amp-lightbox/1.0/amp-lightbox.js b/extensions/amp-lightbox/1.0/amp-lightbox.js
index 25075b0ba7bc..2685d638a910 100644
--- a/extensions/amp-lightbox/1.0/amp-lightbox.js
+++ b/extensions/amp-lightbox/1.0/amp-lightbox.js
@@ -21,7 +21,7 @@ import {Services} from '../../../src/services';
 import {createCustomEvent} from '../../../src/event-helper';
 import {isExperimentOn} from '../../../src/experiments';
 import {toWin} from '../../../src/types';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /** @const {string} */
 const TAG = 'amp-lightbox';
diff --git a/extensions/amp-live-list/0.1/live-list-manager.js b/extensions/amp-live-list/0.1/live-list-manager.js
index b77d85d13c0a..8d7ee299eb56 100644
--- a/extensions/amp-live-list/0.1/live-list-manager.js
+++ b/extensions/amp-live-list/0.1/live-list-manager.js
@@ -21,7 +21,7 @@ import {fetchDocument} from '../../../src/document-fetcher';
 import {getMode} from '../../../src/mode';
 import {getServicePromiseForDoc} from '../../../src/service';
 import {toArray} from '../../../src/types';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /** @const {string} */
 export const SERVICE_ID = 'liveListManager';
diff --git a/extensions/amp-megaphone/0.1/amp-megaphone.js b/extensions/amp-megaphone/0.1/amp-megaphone.js
index 43fe311c31f7..426be01447be 100644
--- a/extensions/amp-megaphone/0.1/amp-megaphone.js
+++ b/extensions/amp-megaphone/0.1/amp-megaphone.js
@@ -36,7 +36,7 @@ import {isObject} from '../../../src/types';
 import {removeElement} from '../../../src/dom';
 import {setIsMediaComponent} from '../../../src/video-interface';
 import {tryParseJson} from '../../../src/json';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 class AmpMegaphone extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-next-page/1.0/page.js b/extensions/amp-next-page/1.0/page.js
index 53f70fc768a3..e39c558ffd6f 100644
--- a/extensions/amp-next-page/1.0/page.js
+++ b/extensions/amp-next-page/1.0/page.js
@@ -16,7 +16,7 @@
 
 import {ViewportRelativePos} from './visibility-observer';
 import {VisibilityState} from '../../../src/visibility-state';
-import {pureDevAssert as devAssert} from '../../../src/pure-assert';
+import {pureDevAssert as devAssert} from '../../../src/assert';
 
 /** @enum {number} */
 export const PageState = {
diff --git a/extensions/amp-next-page/1.0/visibility-observer.js b/extensions/amp-next-page/1.0/visibility-observer.js
index 82679fa3205c..c35ea56d4b0a 100644
--- a/extensions/amp-next-page/1.0/visibility-observer.js
+++ b/extensions/amp-next-page/1.0/visibility-observer.js
@@ -24,7 +24,7 @@ import {
 } from '../../../src/service/position-observer/position-observer-impl';
 import {RelativePositions} from '../../../src/layout-rect';
 import {Services} from '../../../src/services';
-import {pureDevAssert as devAssert} from '../../../src/pure-assert';
+import {pureDevAssert as devAssert} from '../../../src/assert';
 import {throttle} from '../../../src/utils/rate-limit';
 
 /** @enum {number} */
diff --git a/extensions/amp-o2-player/0.1/amp-o2-player.js b/extensions/amp-o2-player/0.1/amp-o2-player.js
index c87b4876004a..6a73261f09f0 100644
--- a/extensions/amp-o2-player/0.1/amp-o2-player.js
+++ b/extensions/amp-o2-player/0.1/amp-o2-player.js
@@ -25,7 +25,7 @@ import {
 import {isLayoutSizeDefined} from '../../../src/layout';
 import {listenFor} from '../../../src/iframe-helper';
 import {setIsMediaComponent} from '../../../src/video-interface';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 class AmpO2Player extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-orientation-observer/0.1/amp-orientation-observer.js b/extensions/amp-orientation-observer/0.1/amp-orientation-observer.js
index c273a93e40d9..5a847c41eb8d 100644
--- a/extensions/amp-orientation-observer/0.1/amp-orientation-observer.js
+++ b/extensions/amp-orientation-observer/0.1/amp-orientation-observer.js
@@ -19,7 +19,7 @@ import {Services} from '../../../src/services';
 import {clamp, sum} from '../../../src/utils/math';
 import {createCustomEvent} from '../../../src/event-helper';
 import {dict} from '../../../src/utils/object';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 const TAG = 'amp-orientation-observer';
 /**
diff --git a/extensions/amp-pinterest/0.1/follow-button.js b/extensions/amp-pinterest/0.1/follow-button.js
index e5d2fd4888da..ae852e1f803b 100644
--- a/extensions/amp-pinterest/0.1/follow-button.js
+++ b/extensions/amp-pinterest/0.1/follow-button.js
@@ -19,7 +19,7 @@ import {assertHttpsUrl} from '../../../src/url';
 import {openWindowDialog} from '../../../src/dom';
 import {tryResolve} from '../../../src/utils/promise';
 
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 // Popup options
 const POP_FOLLOW = `status=no,resizable=yes,scrollbars=yes,
diff --git a/extensions/amp-recaptcha-input/0.1/amp-recaptcha-input.js b/extensions/amp-recaptcha-input/0.1/amp-recaptcha-input.js
index e4d9b1cd5faf..dd4fcd1a85da 100644
--- a/extensions/amp-recaptcha-input/0.1/amp-recaptcha-input.js
+++ b/extensions/amp-recaptcha-input/0.1/amp-recaptcha-input.js
@@ -31,7 +31,7 @@ import {
 import {CSS} from '../../../build/amp-recaptcha-input-0.1.css';
 import {Layout} from '../../../src/layout';
 import {setStyles, toggle} from '../../../src/style';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /** @const */
 const TAG = 'amp-recaptcha-input';
diff --git a/extensions/amp-redbull-player/0.1/amp-redbull-player.js b/extensions/amp-redbull-player/0.1/amp-redbull-player.js
index cae4ae6e60b6..740ccdd34499 100644
--- a/extensions/amp-redbull-player/0.1/amp-redbull-player.js
+++ b/extensions/amp-redbull-player/0.1/amp-redbull-player.js
@@ -33,7 +33,7 @@ import {
 import {getData, listen} from '../../../src/event-helper';
 import {installVideoManagerForDoc} from '../../../src/service/video-manager-impl';
 import {isLayoutSizeDefined} from '../../../src/layout';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /** @private @const */
 const TAG = 'amp-redbull-player';
diff --git a/extensions/amp-reddit/0.1/amp-reddit.js b/extensions/amp-reddit/0.1/amp-reddit.js
index 63e93faf2bc0..f9f281bf6337 100644
--- a/extensions/amp-reddit/0.1/amp-reddit.js
+++ b/extensions/amp-reddit/0.1/amp-reddit.js
@@ -18,7 +18,7 @@ import {Services} from '../../../src/services';
 import {getIframe, preloadBootstrap} from '../../../src/3p-frame';
 import {isLayoutSizeDefined} from '../../../src/layout';
 import {listenFor} from '../../../src/iframe-helper';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 class AmpReddit extends AMP.BaseElement {
   /**
diff --git a/extensions/amp-riddle-quiz/0.1/amp-riddle-quiz.js b/extensions/amp-riddle-quiz/0.1/amp-riddle-quiz.js
index 64c1b3275920..8a97e9b94906 100644
--- a/extensions/amp-riddle-quiz/0.1/amp-riddle-quiz.js
+++ b/extensions/amp-riddle-quiz/0.1/amp-riddle-quiz.js
@@ -17,7 +17,7 @@ import {getData, listen} from './../../../src/event-helper';
 import {isFiniteNumber, isObject} from '../../../src/types';
 import {isLayoutSizeDefined} from '../../../src/layout';
 import {removeElement} from '../../../src/dom';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 export class AmpRiddleQuiz extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-selector/1.0/amp-selector.js b/extensions/amp-selector/1.0/amp-selector.js
index a6b3b5906efe..18822bbc7af2 100644
--- a/extensions/amp-selector/1.0/amp-selector.js
+++ b/extensions/amp-selector/1.0/amp-selector.js
@@ -22,7 +22,7 @@ import {createCustomEvent} from '../../../src/event-helper';
 import {dict} from '../../../src/utils/object';
 import {isExperimentOn} from '../../../src/experiments';
 import {toWin} from '../../../src/types';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /** @const {string} */
 const TAG = 'amp-selector';
diff --git a/extensions/amp-sidebar/1.0/amp-sidebar.js b/extensions/amp-sidebar/1.0/amp-sidebar.js
index b3725e5b4696..26a63073497a 100644
--- a/extensions/amp-sidebar/1.0/amp-sidebar.js
+++ b/extensions/amp-sidebar/1.0/amp-sidebar.js
@@ -21,7 +21,7 @@ import {Sidebar} from './sidebar';
 import {dict} from '../../../src/utils/object';
 import {isExperimentOn} from '../../../src/experiments';
 import {toggle} from '../../../src/style';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /** @const {string} */
 const TAG = 'amp-sidebar';
diff --git a/extensions/amp-skimlinks/0.1/link-rewriter/link-rewriter.js b/extensions/amp-skimlinks/0.1/link-rewriter/link-rewriter.js
index 86dff6348224..3a5beae5fd8e 100644
--- a/extensions/amp-skimlinks/0.1/link-rewriter/link-rewriter.js
+++ b/extensions/amp-skimlinks/0.1/link-rewriter/link-rewriter.js
@@ -19,7 +19,7 @@ import {EVENTS, ORIGINAL_URL_ATTRIBUTE} from './constants';
 import {LinkReplacementCache} from './link-replacement-cache';
 import {Observable} from '../../../../src/observable';
 import {TwoStepsResponse} from './two-steps-response';
-import {pureUserAssert as userAssert} from '../../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../../src/assert';
 
 /** @typedef {!Array<{anchor: !HTMLElement, replacementUrl: ?string}>}} */
 export let AnchorReplacementList;
diff --git a/extensions/amp-skimlinks/0.1/skim-options.js b/extensions/amp-skimlinks/0.1/skim-options.js
index 64a1c4593686..84ff78d4b453 100644
--- a/extensions/amp-skimlinks/0.1/skim-options.js
+++ b/extensions/amp-skimlinks/0.1/skim-options.js
@@ -16,7 +16,7 @@
 
 import {getChildJsonConfig} from '../../../src/json';
 import {getNormalizedHostnameFromUrl} from './utils';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 import {
   DEFAULT_CONFIG,
diff --git a/extensions/amp-social-share/1.0/amp-social-share.js b/extensions/amp-social-share/1.0/amp-social-share.js
index 342cfc89147a..9e81e06be343 100644
--- a/extensions/amp-social-share/1.0/amp-social-share.js
+++ b/extensions/amp-social-share/1.0/amp-social-share.js
@@ -26,7 +26,7 @@ import {getSocialConfig} from './social-share-config';
 import {isExperimentOn} from '../../../src/experiments';
 import {toWin} from '../../../src/types';
 import {toggle} from '../../../src/style';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /** @const {string} */
 const TAG = 'amp-social-share';
diff --git a/extensions/amp-soundcloud/0.1/amp-soundcloud.js b/extensions/amp-soundcloud/0.1/amp-soundcloud.js
index 85e13646c52e..4ca42ca338db 100644
--- a/extensions/amp-soundcloud/0.1/amp-soundcloud.js
+++ b/extensions/amp-soundcloud/0.1/amp-soundcloud.js
@@ -31,7 +31,7 @@ import {Services} from '../../../src/services';
 import {dict} from '../../../src/utils/object';
 import {isLayoutSizeDefined} from '../../../src/layout';
 import {setIsMediaComponent} from '../../../src/video-interface';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 class AmpSoundcloud extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-springboard-player/0.1/amp-springboard-player.js b/extensions/amp-springboard-player/0.1/amp-springboard-player.js
index d6a591fe0eaf..1c7eefcd90a9 100644
--- a/extensions/amp-springboard-player/0.1/amp-springboard-player.js
+++ b/extensions/amp-springboard-player/0.1/amp-springboard-player.js
@@ -17,7 +17,7 @@
 import {Services} from '../../../src/services';
 import {isLayoutSizeDefined} from '../../../src/layout';
 import {setIsMediaComponent} from '../../../src/video-interface';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 class AmpSpringboardPlayer extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-story-auto-analytics/0.1/amp-story-auto-analytics.js b/extensions/amp-story-auto-analytics/0.1/amp-story-auto-analytics.js
index 56954c2b35da..3306e3baca0d 100644
--- a/extensions/amp-story-auto-analytics/0.1/amp-story-auto-analytics.js
+++ b/extensions/amp-story-auto-analytics/0.1/amp-story-auto-analytics.js
@@ -16,7 +16,7 @@
 
 import {Services} from '../../../src/services';
 import {buildGtagConfig} from './auto-analytics-configs.js';
-import {pureDevAssert as devAssert} from '../../../src/pure-assert';
+import {pureDevAssert as devAssert} from '../../../src/assert';
 import {htmlFor} from '../../../src/static-template';
 
 const buildAutoAnalyticsTemplate = (element) => {
diff --git a/extensions/amp-story/1.0/animation-presets.js b/extensions/amp-story/1.0/animation-presets.js
index d6fa99607442..1babbb8e21f4 100644
--- a/extensions/amp-story/1.0/animation-presets.js
+++ b/extensions/amp-story/1.0/animation-presets.js
@@ -24,7 +24,7 @@ import {
   whooshIn,
 } from './animation-presets-utils';
 import {px} from '../../../src/style';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /** @const {string} */
 const FULL_BLEED_CATEGORY = 'full-bleed';
diff --git a/extensions/amp-story/1.0/bookend/components/article.js b/extensions/amp-story/1.0/bookend/components/article.js
index beedff817c52..9e43259cc636 100644
--- a/extensions/amp-story/1.0/bookend/components/article.js
+++ b/extensions/amp-story/1.0/bookend/components/article.js
@@ -28,7 +28,7 @@ import {
 } from '../../utils';
 import {getSourceUrl, resolveRelativeUrl} from '../../../../../src/url';
 import {htmlFor, htmlRefs} from '../../../../../src/static-template';
-import {pureUserAssert as userAssert} from '../../../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../../../src/assert';
 
 /**
  * @typedef {{
diff --git a/extensions/amp-story/1.0/bookend/components/cta-link.js b/extensions/amp-story/1.0/bookend/components/cta-link.js
index 1bd817f1c8c0..49c59dc66e31 100644
--- a/extensions/amp-story/1.0/bookend/components/cta-link.js
+++ b/extensions/amp-story/1.0/bookend/components/cta-link.js
@@ -24,7 +24,7 @@ import {dict} from '../../../../../src/utils/object';
 import {getSourceUrl, resolveRelativeUrl} from '../../../../../src/url';
 import {htmlFor, htmlRefs} from '../../../../../src/static-template';
 import {isArray} from '../../../../../src/types';
-import {pureUserAssert as userAssert} from '../../../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../../../src/assert';
 import {userAssertValidProtocol} from '../../utils';
 
 /**
diff --git a/extensions/amp-story/1.0/bookend/components/heading.js b/extensions/amp-story/1.0/bookend/components/heading.js
index 22d060134581..fd777d14397f 100644
--- a/extensions/amp-story/1.0/bookend/components/heading.js
+++ b/extensions/amp-story/1.0/bookend/components/heading.js
@@ -20,7 +20,7 @@ import {
   BookendComponentInterface,
 } from './bookend-component-interface';
 import {htmlFor} from '../../../../../src/static-template';
-import {pureUserAssert as userAssert} from '../../../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../../../src/assert';
 
 /**
  * @typedef {{
diff --git a/extensions/amp-story/1.0/bookend/components/landscape.js b/extensions/amp-story/1.0/bookend/components/landscape.js
index eeb90bb99ddb..b9fe162f8a91 100644
--- a/extensions/amp-story/1.0/bookend/components/landscape.js
+++ b/extensions/amp-story/1.0/bookend/components/landscape.js
@@ -28,7 +28,7 @@ import {
 } from '../../utils';
 import {getSourceUrl, resolveRelativeUrl} from '../../../../../src/url';
 import {htmlFor, htmlRefs} from '../../../../../src/static-template';
-import {pureUserAssert as userAssert} from '../../../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../../../src/assert';
 
 /**
  * @typedef {{
diff --git a/extensions/amp-story/1.0/bookend/components/portrait.js b/extensions/amp-story/1.0/bookend/components/portrait.js
index a161b6b1e756..d8be6ee1b0d7 100644
--- a/extensions/amp-story/1.0/bookend/components/portrait.js
+++ b/extensions/amp-story/1.0/bookend/components/portrait.js
@@ -28,7 +28,7 @@ import {
 } from '../../utils';
 import {getSourceUrl, resolveRelativeUrl} from '../../../../../src/url';
 import {htmlFor, htmlRefs} from '../../../../../src/static-template';
-import {pureUserAssert as userAssert} from '../../../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../../../src/assert';
 
 /**
  * @typedef {{
diff --git a/extensions/amp-story/1.0/bookend/components/text-box.js b/extensions/amp-story/1.0/bookend/components/text-box.js
index 22e1b558965e..4e576579d106 100644
--- a/extensions/amp-story/1.0/bookend/components/text-box.js
+++ b/extensions/amp-story/1.0/bookend/components/text-box.js
@@ -21,7 +21,7 @@ import {
 } from './bookend-component-interface';
 import {htmlFor} from '../../../../../src/static-template';
 import {isArray} from '../../../../../src/types';
-import {pureUserAssert as userAssert} from '../../../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../../../src/assert';
 
 /**
  * @typedef {{
diff --git a/extensions/amp-story/1.0/live-story-manager.js b/extensions/amp-story/1.0/live-story-manager.js
index 7b3a07fcc4e1..52425294ee79 100644
--- a/extensions/amp-story/1.0/live-story-manager.js
+++ b/extensions/amp-story/1.0/live-story-manager.js
@@ -19,7 +19,7 @@ import {CommonSignals} from '../../../src/common-signals';
 import {Services} from '../../../src/services';
 import {createElementWithAttributes, lastChildElement} from '../../../src/dom';
 import {dict} from '../../../src/utils/object';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /**
  * Property used for storing id of custom slot. This custom slot can be used to
diff --git a/extensions/amp-story/1.0/pagination-buttons.js b/extensions/amp-story/1.0/pagination-buttons.js
index 2c2305890dd0..6eea2756b2ca 100644
--- a/extensions/amp-story/1.0/pagination-buttons.js
+++ b/extensions/amp-story/1.0/pagination-buttons.js
@@ -24,7 +24,7 @@ import {CommonSignals} from '../../../src/common-signals';
 import {EventType, dispatch} from './events';
 import {Services} from '../../../src/services';
 import {dev} from '../../../src/log';
-import {pureDevAssert as devAssert} from '../../../src/pure-assert';
+import {pureDevAssert as devAssert} from '../../../src/assert';
 import {htmlFor} from '../../../src/static-template';
 
 /** @struct @typedef {{className: string, triggers: (string|undefined)}} */
diff --git a/extensions/amp-story/1.0/simple-template.js b/extensions/amp-story/1.0/simple-template.js
index d825ed23faa2..62fcd9619946 100644
--- a/extensions/amp-story/1.0/simple-template.js
+++ b/extensions/amp-story/1.0/simple-template.js
@@ -15,7 +15,7 @@
  */
 import {LocalizedStringId} from '../../../src/localized-strings'; // eslint-disable-line no-unused-vars
 import {createElementWithAttributes} from '../../../src/dom';
-import {pureDevAssert as devAssert} from '../../../src/pure-assert';
+import {pureDevAssert as devAssert} from '../../../src/assert';
 import {getLocalizationService} from './amp-story-localization-service';
 import {hasOwn} from '../../../src/utils/object';
 import {isArray} from '../../../src/types';
diff --git a/extensions/amp-stream-gallery/1.0/amp-stream-gallery.js b/extensions/amp-stream-gallery/1.0/amp-stream-gallery.js
index ff595047e026..c363b3525204 100644
--- a/extensions/amp-stream-gallery/1.0/amp-stream-gallery.js
+++ b/extensions/amp-stream-gallery/1.0/amp-stream-gallery.js
@@ -25,7 +25,7 @@ import {createCustomEvent} from '../../../src/event-helper';
 import {dict} from '../../../src/utils/object';
 import {dispatchCustomEvent} from '../../../src/dom';
 import {isExperimentOn} from '../../../src/experiments';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /** @const {string} */
 const TAG = 'amp-stream-gallery';
diff --git a/extensions/amp-timeago/0.1/amp-timeago.js b/extensions/amp-timeago/0.1/amp-timeago.js
index f3c98166a2dc..a034d97f3563 100644
--- a/extensions/amp-timeago/0.1/amp-timeago.js
+++ b/extensions/amp-timeago/0.1/amp-timeago.js
@@ -20,7 +20,7 @@ import {
   observeWithSharedInOb,
   unobserveWithSharedInOb,
 } from '../../../src/viewport-observer';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 export class AmpTimeAgo extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-timeago/1.0/amp-timeago.js b/extensions/amp-timeago/1.0/amp-timeago.js
index 5262d21ee18d..c2d91d086ea7 100644
--- a/extensions/amp-timeago/1.0/amp-timeago.js
+++ b/extensions/amp-timeago/1.0/amp-timeago.js
@@ -16,7 +16,7 @@
 
 import {BaseElement} from './base-element';
 import {isExperimentOn} from '../../../src/experiments';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /** @const {string} */
 const TAG = 'amp-timeago';
diff --git a/extensions/amp-truncate-text/0.1/binary-search.js b/extensions/amp-truncate-text/0.1/binary-search.js
index 861dffc608b7..c1d3b3dd4afd 100644
--- a/extensions/amp-truncate-text/0.1/binary-search.js
+++ b/extensions/amp-truncate-text/0.1/binary-search.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {pureDevAssert as devAssert} from '../../../src/pure-assert';
+import {pureDevAssert as devAssert} from '../../../src/assert';
 
 /**
  * When no matching index is found, whether to stop on the next or previous
diff --git a/extensions/amp-video/1.0/amp-video.js b/extensions/amp-video/1.0/amp-video.js
index 292698890ba7..8dc0b7d98eb1 100644
--- a/extensions/amp-video/1.0/amp-video.js
+++ b/extensions/amp-video/1.0/amp-video.js
@@ -17,7 +17,7 @@
 import {CSS} from '../../../build/amp-video-1.0.css';
 import {VideoBaseElement} from './base-element';
 import {isExperimentOn} from '../../../src/experiments';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /** @const {string} */
 const TAG = 'amp-video';
diff --git a/extensions/amp-viewer-integration/0.1/findtext.js b/extensions/amp-viewer-integration/0.1/findtext.js
index 637d16bf80b1..6cb3542f2826 100644
--- a/extensions/amp-viewer-integration/0.1/findtext.js
+++ b/extensions/amp-viewer-integration/0.1/findtext.js
@@ -15,7 +15,7 @@
  */
 
 import {computedStyle} from '../../../src/style';
-import {pureDevAssert as devAssert} from '../../../src/pure-assert';
+import {pureDevAssert as devAssert} from '../../../src/assert';
 
 /**
  * Simple implementation of CircularBuffer.
diff --git a/extensions/amp-vimeo/0.1/amp-vimeo.js b/extensions/amp-vimeo/0.1/amp-vimeo.js
index 47d04e101d12..251bf08b7617 100644
--- a/extensions/amp-vimeo/0.1/amp-vimeo.js
+++ b/extensions/amp-vimeo/0.1/amp-vimeo.js
@@ -32,7 +32,7 @@ import {getMode} from '../../../src/mode';
 import {installVideoManagerForDoc} from '../../../src/service/video-manager-impl';
 import {isLayoutSizeDefined} from '../../../src/layout';
 import {once} from '../../../src/utils/function';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 const TAG = 'amp-vimeo';
 
diff --git a/extensions/amp-vine/0.1/amp-vine.js b/extensions/amp-vine/0.1/amp-vine.js
index 3aa9cca4aae7..e31a14ea1b94 100644
--- a/extensions/amp-vine/0.1/amp-vine.js
+++ b/extensions/amp-vine/0.1/amp-vine.js
@@ -16,7 +16,7 @@
 
 import {Services} from '../../../src/services';
 import {isLayoutSizeDefined} from '../../../src/layout';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 class AmpVine extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-yotpo/0.1/amp-yotpo.js b/extensions/amp-yotpo/0.1/amp-yotpo.js
index a516f4b150cc..8b8ec4287376 100644
--- a/extensions/amp-yotpo/0.1/amp-yotpo.js
+++ b/extensions/amp-yotpo/0.1/amp-yotpo.js
@@ -19,7 +19,7 @@ import {getIframe} from '../../../src/3p-frame';
 import {isLayoutSizeDefined} from '../../../src/layout';
 import {listenFor} from '../../../src/iframe-helper';
 import {removeElement} from '../../../src/dom';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 export class AmpYotpo extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-youtube/1.0/amp-youtube.js b/extensions/amp-youtube/1.0/amp-youtube.js
index 1617bca32e56..7ff9b7ccd544 100644
--- a/extensions/amp-youtube/1.0/amp-youtube.js
+++ b/extensions/amp-youtube/1.0/amp-youtube.js
@@ -17,7 +17,7 @@
 import {BaseElement} from './base-element';
 import {CSS} from '../../../build/amp-youtube-1.0.css';
 import {isExperimentOn} from '../../../src/experiments';
-import {pureUserAssert as userAssert} from '../../../src/pure-assert';
+import {pureUserAssert as userAssert} from '../../../src/assert';
 
 /** @const {string} */
 const TAG = 'amp-youtube';
diff --git a/src/action-constants.js b/src/action-constants.js
index 452d353e998d..58b2aad23c7b 100644
--- a/src/action-constants.js
+++ b/src/action-constants.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {pureDevAssert as devAssert} from './pure-assert';
+import {pureDevAssert as devAssert} from './assert';
 
 /**
  * Key string in an action arguments map for an unparsed object literal string.
diff --git a/src/context/component-hooks.js b/src/context/component-hooks.js
index 0f71e6e89336..c4fd533b8626 100644
--- a/src/context/component-hooks.js
+++ b/src/context/component-hooks.js
@@ -15,7 +15,7 @@
  */
 
 import {areEqualOrdered} from '../utils/array';
-import {pureDevAssert as devAssert} from '../pure-assert';
+import {pureDevAssert as devAssert} from '../assert';
 import {tryCallback} from './scheduler';
 
 const EMPTY_DEPS = [];
diff --git a/src/context/node.js b/src/context/node.js
index d81a31f8b1af..db8ea3e230eb 100644
--- a/src/context/node.js
+++ b/src/context/node.js
@@ -15,7 +15,7 @@
  */
 
 import {Values} from './values';
-import {pureDevAssert as devAssert} from '../pure-assert';
+import {pureDevAssert as devAssert} from '../assert';
 import {getMode} from '../mode';
 import {pushIfNotExist, removeItem} from '../utils/array';
 import {throttleTail} from './scheduler';
diff --git a/src/context/prop.js b/src/context/prop.js
index a579c64380f8..7a0a65ec1011 100644
--- a/src/context/prop.js
+++ b/src/context/prop.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {pureDevAssert as devAssert} from '../pure-assert';
+import {pureDevAssert as devAssert} from '../assert';
 
 const EMPTY_DEPS = [];
 
diff --git a/src/cookies.js b/src/cookies.js
index 36b441c55243..97a7de791621 100644
--- a/src/cookies.js
+++ b/src/cookies.js
@@ -22,7 +22,7 @@ import {
   tryDecodeUriComponent,
 } from './url';
 import {urls} from './config';
-import {pureUserAssert as userAssert} from './pure-assert';
+import {pureUserAssert as userAssert} from './assert';
 
 const TEST_COOKIE_NAME = '-test-amp-cookie-tmp';
 
diff --git a/src/css.js b/src/css.js
index 083a23015a8f..2be4ebb30af9 100644
--- a/src/css.js
+++ b/src/css.js
@@ -15,7 +15,7 @@
  */
 
 import {cssEscape} from '../third_party/css-escape/css-escape';
-import {pureDevAssert as devAssert} from './pure-assert';
+import {pureDevAssert as devAssert} from './assert';
 
 /**
  * Asserts that name is just an alphanumeric word, and does not contain
diff --git a/src/element-service.js b/src/element-service.js
index aa79a1761829..e998eaa3d4d7 100644
--- a/src/element-service.js
+++ b/src/element-service.js
@@ -24,7 +24,7 @@ import {
   getServicePromiseOrNull,
   getServicePromiseOrNullForDoc,
 } from './service';
-import {pureUserAssert as userAssert} from './pure-assert';
+import {pureUserAssert as userAssert} from './assert';
 
 /**
  * Returns a promise for a service for the given id and window. Also expects an
diff --git a/src/extension-analytics.js b/src/extension-analytics.js
index 9fc182a4b259..b2fb74841b57 100644
--- a/src/extension-analytics.js
+++ b/src/extension-analytics.js
@@ -17,7 +17,7 @@
 import {CommonSignals} from './common-signals';
 import {Services} from './services';
 import {createElementWithAttributes, removeElement} from './dom';
-import {pureDevAssert as devAssert} from './pure-assert';
+import {pureDevAssert as devAssert} from './assert';
 import {dict} from './utils/object';
 import {isArray, toWin} from './types';
 import {triggerAnalyticsEvent} from './analytics';
diff --git a/src/finite-state-machine.js b/src/finite-state-machine.js
index ce33ba51c75d..f54a4041be3e 100644
--- a/src/finite-state-machine.js
+++ b/src/finite-state-machine.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {pureDevAssert as devAssert} from './pure-assert';
+import {pureDevAssert as devAssert} from './assert';
 
 /**
  * @template STATE
diff --git a/src/gesture.js b/src/gesture.js
index 860b5d189fdb..de067e04b6a0 100644
--- a/src/gesture.js
+++ b/src/gesture.js
@@ -16,7 +16,7 @@
 
 import {Observable} from './observable';
 import {Pass} from './pass';
-import {pureDevAssert as devAssert} from './pure-assert';
+import {pureDevAssert as devAssert} from './assert';
 import {findIndex} from './utils/array';
 import {supportsPassiveEventListener} from './event-helper-listen';
 import {toWin} from './types';
diff --git a/src/modal.js b/src/modal.js
index 8e7e30a9810c..af65ef1278a2 100644
--- a/src/modal.js
+++ b/src/modal.js
@@ -1,4 +1,4 @@
-import {pureDevAssert as devAssert} from './pure-assert';
+import {pureDevAssert as devAssert} from './assert';
 import {isConnectedNode, rootNodeFor} from './dom';
 import {toArray} from './types';
 
diff --git a/src/preact/base-element.js b/src/preact/base-element.js
index 248a7d5d148f..391c607a4bbc 100644
--- a/src/preact/base-element.js
+++ b/src/preact/base-element.js
@@ -40,7 +40,7 @@ import {
   parseBooleanAttribute,
 } from '../dom';
 import {dashToCamelCase} from '../string';
-import {pureDevAssert as devAssert} from '../pure-assert';
+import {pureDevAssert as devAssert} from '../assert';
 import {dict, hasOwn, map} from '../utils/object';
 import {getDate} from '../utils/date';
 import {getMode} from '../mode';
diff --git a/src/render-delaying-services.js b/src/render-delaying-services.js
index 8b4b912614ae..cf7ebf6325b6 100644
--- a/src/render-delaying-services.js
+++ b/src/render-delaying-services.js
@@ -15,7 +15,7 @@
  */
 
 import {Services} from './services';
-import {pureDevAssert as devAssert} from './pure-assert';
+import {pureDevAssert as devAssert} from './assert';
 import {getServicePromise} from './service';
 
 /**
diff --git a/src/service/core-services.js b/src/service/core-services.js
index e581d0d4cfec..7dff1350a3e9 100644
--- a/src/service/core-services.js
+++ b/src/service/core-services.js
@@ -15,7 +15,7 @@
  */
 
 import {adoptServiceForEmbedDoc} from '../service';
-import {pureDevAssert as devAssert} from '../pure-assert';
+import {pureDevAssert as devAssert} from '../assert';
 import {installActionServiceForDoc} from './action-impl';
 import {installBatchedXhrService} from './batched-xhr-impl';
 import {installCidService} from './cid-impl';
diff --git a/src/service/custom-element-registry.js b/src/service/custom-element-registry.js
index 43de2f2b9ef7..8a3142f7d113 100644
--- a/src/service/custom-element-registry.js
+++ b/src/service/custom-element-registry.js
@@ -19,7 +19,7 @@ import {Services} from '../services';
 import {createCustomElementClass, stubbedElements} from '../custom-element';
 import {extensionScriptsInNode} from '../element-service';
 import {reportError} from '../error';
-import {pureUserAssert as userAssert} from '../pure-assert';
+import {pureUserAssert as userAssert} from '../assert';
 
 /**
  * @param {!Window} win
diff --git a/src/service/hidden-observer-impl.js b/src/service/hidden-observer-impl.js
index 8c37adaa9ae5..b4e7c16d89a8 100644
--- a/src/service/hidden-observer-impl.js
+++ b/src/service/hidden-observer-impl.js
@@ -15,7 +15,7 @@
  */
 
 import {Observable} from '../observable';
-import {pureDevAssert as devAssert} from '../pure-assert';
+import {pureDevAssert as devAssert} from '../assert';
 import {registerServiceBuilderForDoc} from '../service';
 
 /**
diff --git a/src/service/owners-impl.js b/src/service/owners-impl.js
index 96d154208a77..da654b18791f 100644
--- a/src/service/owners-impl.js
+++ b/src/service/owners-impl.js
@@ -17,7 +17,7 @@
 import {OwnersInterface} from './owners-interface';
 import {Resource} from './resource';
 import {Services} from '../services';
-import {pureDevAssert as devAssert} from '../pure-assert';
+import {pureDevAssert as devAssert} from '../assert';
 import {isArray} from '../types';
 import {registerServiceBuilderForDoc} from '../service';
 
diff --git a/src/service/position-observer/position-observer-worker.js b/src/service/position-observer/position-observer-worker.js
index 9d3e2b332cff..89dca611678e 100644
--- a/src/service/position-observer/position-observer-worker.js
+++ b/src/service/position-observer/position-observer-worker.js
@@ -15,7 +15,7 @@
  */
 
 import {Services} from '../../services';
-import {pureDevAssert as devAssert} from '../../pure-assert';
+import {pureDevAssert as devAssert} from '../../assert';
 import {
   layoutRectEquals,
   layoutRectLtwh,
diff --git a/src/service/task-queue.js b/src/service/task-queue.js
index feb2a9a37eac..b70a5488c8b0 100644
--- a/src/service/task-queue.js
+++ b/src/service/task-queue.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {pureDevAssert as devAssert} from '../pure-assert';
+import {pureDevAssert as devAssert} from '../assert';
 
 /**
  * The internal structure for the task.
diff --git a/src/service/template-impl.js b/src/service/template-impl.js
index dd19f77f1f92..e31e938e403e 100644
--- a/src/service/template-impl.js
+++ b/src/service/template-impl.js
@@ -17,7 +17,7 @@
 import {Deferred} from '../utils/promise';
 import {getService, registerServiceBuilder} from '../service';
 import {rootNodeFor, scopedQuerySelector} from '../dom';
-import {pureUserAssert as userAssert} from '../pure-assert';
+import {pureUserAssert as userAssert} from '../assert';
 
 /**
  * @fileoverview
diff --git a/src/service/variable-source.js b/src/service/variable-source.js
index 3602faadc8be..d8a41df78bb9 100644
--- a/src/service/variable-source.js
+++ b/src/service/variable-source.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 import {Services} from '../services';
-import {pureDevAssert as devAssert} from '../pure-assert';
+import {pureDevAssert as devAssert} from '../assert';
 import {isAmp4Email} from '../format';
 import {isFiniteNumber} from '../types';
 import {loadPromise} from '../event-helper';
diff --git a/src/ssr-template-helper.js b/src/ssr-template-helper.js
index 5656f86bb6e7..41bf47c99946 100644
--- a/src/ssr-template-helper.js
+++ b/src/ssr-template-helper.js
@@ -17,7 +17,7 @@
 import {dict} from './utils/object';
 import {isArray} from './types';
 import {toStructuredCloneable} from './utils/xhr-utils';
-import {pureUserAssert as userAssert} from './pure-assert';
+import {pureUserAssert as userAssert} from './assert';
 
 /**
  * @typedef {{
diff --git a/src/static-template.js b/src/static-template.js
index 69ca1d5e2600..e6b8422274a7 100644
--- a/src/static-template.js
+++ b/src/static-template.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {pureDevAssert as devAssert} from './pure-assert';
+import {pureDevAssert as devAssert} from './assert';
 import {map} from './utils/object.js';
 
 let htmlContainer;
diff --git a/src/url.js b/src/url.js
index 4210325274a2..27182c446ed0 100644
--- a/src/url.js
+++ b/src/url.js
@@ -22,7 +22,7 @@ import {isArray} from './types';
 import {parseQueryString_} from './url-parse-query-string';
 import {tryDecodeUriComponent_} from './url-try-decode-uri-component';
 import {urls} from './config';
-import {pureUserAssert as userAssert} from './pure-assert';
+import {pureUserAssert as userAssert} from './assert';
 
 /**
  * @type {!JsonObject}
diff --git a/src/utils/bytes.js b/src/utils/bytes.js
index e38ce5ffb244..a137d5872d80 100644
--- a/src/utils/bytes.js
+++ b/src/utils/bytes.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {pureDevAssert as devAssert} from '../pure-assert';
+import {pureDevAssert as devAssert} from '../assert';
 
 /**
  * Interpret a byte array as a UTF-8 string.
diff --git a/src/utils/detached-dom-stream.js b/src/utils/detached-dom-stream.js
index de0c3ecf76a9..1e25e985eb9a 100644
--- a/src/utils/detached-dom-stream.js
+++ b/src/utils/detached-dom-stream.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {pureDevAssert as devAssert} from '../pure-assert';
+import {pureDevAssert as devAssert} from '../assert';
 
 export class DetachedDomStream {
   /**
diff --git a/src/utils/math.js b/src/utils/math.js
index 3b9953066482..3623e881519c 100644
--- a/src/utils/math.js
+++ b/src/utils/math.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {pureDevAssert as devAssert} from '../pure-assert';
+import {pureDevAssert as devAssert} from '../assert';
 
 /**
  * Maps a value in a first range to its equivalent in a second range
diff --git a/src/viewport-observer.js b/src/viewport-observer.js
index d8db36e01194..f81385673e5d 100644
--- a/src/viewport-observer.js
+++ b/src/viewport-observer.js
@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-import {pureDevAssert as devAssert} from '../src/pure-assert';
+import {pureDevAssert as devAssert} from '../src/assert';
 import {getMode} from './mode';
 import {isIframed} from './dom';
 import {toWin} from './types';

From 2e67505afbc46e2eadbbfe85816b1c3afa02c959 Mon Sep 17 00:00:00 2001
From: Ryan Cebulko <ryan@cebulko.com>
Date: Tue, 23 Feb 2021 13:47:16 -0500
Subject: [PATCH 10/15] allow deps

---
 build-system/test-configs/dep-check-config.js | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/build-system/test-configs/dep-check-config.js b/build-system/test-configs/dep-check-config.js
index 28f83d44ba29..23cfbe1a44e8 100644
--- a/build-system/test-configs/dep-check-config.js
+++ b/build-system/test-configs/dep-check-config.js
@@ -100,6 +100,7 @@ exports.rules = [
       '3p/**->src/utils/function.js',
       '3p/**->src/utils/object.js',
       '3p/**->src/utils/promise.js',
+      '3p/**->src/assert.js',
       '3p/**->src/log.js',
       '3p/**->src/types.js',
       '3p/**->src/string.js',
@@ -135,6 +136,7 @@ exports.rules = [
       'ads/**->src/utils/dom-fingerprint.js',
       'ads/**->src/utils/object.js',
       'ads/**->src/utils/rate-limit.js',
+      'ads/**->src/assert.js',
       'ads/**->src/log.js',
       'ads/**->src/mode.js',
       'ads/**->src/url.js',

From 7da0ef9699ecb84d49d381bea2c0ad3d90af5317 Mon Sep 17 00:00:00 2001
From: Ryan Cebulko <ryan@cebulko.com>
Date: Thu, 25 Feb 2021 12:00:22 -0500
Subject: [PATCH 11/15] Update references to core dir

---
 3p/facebook.js                                                  | 2 +-
 3p/github.js                                                    | 2 +-
 3p/mathml.js                                                    | 2 +-
 ads/vendors/csa.js                                              | 2 +-
 .../__component_version__/amp-__component_name_hyphenated__.js  | 2 +-
 contributing/building-a-bento-amp-extension.md                  | 2 +-
 contributing/building-an-amp-extension.md                       | 2 +-
 extensions/amp-a4a/0.1/amp-ad-template-helper.js                | 2 +-
 extensions/amp-a4a/0.1/friendly-frame-renderer.js               | 2 +-
 extensions/amp-a4a/0.1/template-renderer.js                     | 2 +-
 extensions/amp-access-scroll/0.1/scroll-component.js            | 2 +-
 extensions/amp-accordion/1.0/amp-accordion.js                   | 2 +-
 extensions/amp-accordion/1.0/base-element.js                    | 2 +-
 extensions/amp-action-macro/0.1/amp-action-macro.js             | 2 +-
 extensions/amp-ad-custom/0.1/amp-ad-custom.js                   | 2 +-
 extensions/amp-ad-exit/0.1/filters/click-location.js            | 2 +-
 .../amp-ad-network-adsense-impl/0.1/adsense-shared-state.js     | 2 +-
 .../0.1/test/test-doubleclick-sra.js                            | 2 +-
 extensions/amp-ad/0.1/amp-ad-custom.js                          | 2 +-
 extensions/amp-ad/0.1/amp-ad-ui.js                              | 2 +-
 extensions/amp-ad/0.1/amp-ad.js                                 | 2 +-
 extensions/amp-addthis/0.1/amp-addthis.js                       | 2 +-
 extensions/amp-analytics/0.1/scroll-manager.js                  | 2 +-
 extensions/amp-analytics/0.1/visibility-model.js                | 2 +-
 .../amp-animation/0.1/runners/native-web-animation-runner.js    | 2 +-
 extensions/amp-animation/0.1/runners/utils.js                   | 2 +-
 extensions/amp-auto-ads/0.1/amp-auto-ads.js                     | 2 +-
 extensions/amp-autocomplete/0.1/autocomplete-binding-inline.js  | 2 +-
 extensions/amp-base-carousel/1.0/amp-base-carousel.js           | 2 +-
 .../amp-bodymovin-animation/0.1/amp-bodymovin-animation.js      | 2 +-
 extensions/amp-carousel/0.1/base-slides.js                      | 2 +-
 extensions/amp-connatix-player/0.1/amp-connatix-player.js       | 2 +-
 extensions/amp-delight-player/0.1/amp-delight-player.js         | 2 +-
 extensions/amp-embedly-card/0.1/amp-embedly-card-impl.js        | 2 +-
 extensions/amp-embedly-card/0.1/amp-embedly-key.js              | 2 +-
 extensions/amp-experiment/1.0/mutation-record.js                | 2 +-
 extensions/amp-experiment/1.0/mutation/mutation.js              | 2 +-
 extensions/amp-fit-text/1.0/amp-fit-text.js                     | 2 +-
 .../amp-fx-collection/0.1/providers/amp-fx-presets-utils.js     | 2 +-
 extensions/amp-fx-collection/0.1/providers/fx-provider.js       | 2 +-
 extensions/amp-gwd-animation/0.1/amp-gwd-animation.js           | 2 +-
 extensions/amp-imgur/0.1/amp-imgur.js                           | 2 +-
 .../amp-inline-gallery/0.1/amp-inline-gallery-pagination.js     | 2 +-
 .../amp-inline-gallery/1.0/amp-inline-gallery-pagination.js     | 2 +-
 .../amp-inline-gallery/1.0/amp-inline-gallery-thumbnails.js     | 2 +-
 extensions/amp-inline-gallery/1.0/amp-inline-gallery.js         | 2 +-
 extensions/amp-inputmask/0.1/text-mask.js                       | 2 +-
 extensions/amp-instagram/0.1/amp-instagram.js                   | 2 +-
 extensions/amp-instagram/1.0/amp-instagram.js                   | 2 +-
 extensions/amp-kaltura-player/0.1/amp-kaltura-player.js         | 2 +-
 extensions/amp-lightbox-gallery/0.1/lightbox-controls.js        | 2 +-
 extensions/amp-lightbox/1.0/amp-lightbox.js                     | 2 +-
 extensions/amp-live-list/0.1/live-list-manager.js               | 2 +-
 extensions/amp-megaphone/0.1/amp-megaphone.js                   | 2 +-
 extensions/amp-next-page/1.0/page.js                            | 2 +-
 extensions/amp-next-page/1.0/visibility-observer.js             | 2 +-
 extensions/amp-o2-player/0.1/amp-o2-player.js                   | 2 +-
 .../amp-orientation-observer/0.1/amp-orientation-observer.js    | 2 +-
 extensions/amp-pinterest/0.1/follow-button.js                   | 2 +-
 extensions/amp-recaptcha-input/0.1/amp-recaptcha-input.js       | 2 +-
 extensions/amp-redbull-player/0.1/amp-redbull-player.js         | 2 +-
 extensions/amp-reddit/0.1/amp-reddit.js                         | 2 +-
 extensions/amp-riddle-quiz/0.1/amp-riddle-quiz.js               | 2 +-
 extensions/amp-selector/1.0/amp-selector.js                     | 2 +-
 extensions/amp-selector/1.0/base-element.js                     | 2 +-
 extensions/amp-sidebar/1.0/amp-sidebar.js                       | 2 +-
 extensions/amp-skimlinks/0.1/link-rewriter/link-rewriter.js     | 2 +-
 extensions/amp-skimlinks/0.1/skim-options.js                    | 2 +-
 extensions/amp-social-share/1.0/amp-social-share.js             | 2 +-
 extensions/amp-soundcloud/0.1/amp-soundcloud.js                 | 2 +-
 extensions/amp-springboard-player/0.1/amp-springboard-player.js | 2 +-
 .../amp-story-auto-analytics/0.1/amp-story-auto-analytics.js    | 2 +-
 extensions/amp-story/1.0/animation-presets.js                   | 2 +-
 extensions/amp-story/1.0/bookend/components/article.js          | 2 +-
 extensions/amp-story/1.0/bookend/components/cta-link.js         | 2 +-
 extensions/amp-story/1.0/bookend/components/heading.js          | 2 +-
 extensions/amp-story/1.0/bookend/components/landscape.js        | 2 +-
 extensions/amp-story/1.0/bookend/components/portrait.js         | 2 +-
 extensions/amp-story/1.0/bookend/components/text-box.js         | 2 +-
 extensions/amp-story/1.0/live-story-manager.js                  | 2 +-
 extensions/amp-story/1.0/pagination-buttons.js                  | 2 +-
 extensions/amp-story/1.0/simple-template.js                     | 2 +-
 extensions/amp-stream-gallery/1.0/amp-stream-gallery.js         | 2 +-
 extensions/amp-timeago/0.1/amp-timeago.js                       | 2 +-
 extensions/amp-timeago/1.0/amp-timeago.js                       | 2 +-
 extensions/amp-truncate-text/0.1/binary-search.js               | 2 +-
 extensions/amp-video/1.0/amp-video.js                           | 2 +-
 extensions/amp-viewer-integration/0.1/findtext.js               | 2 +-
 extensions/amp-vimeo/0.1/amp-vimeo.js                           | 2 +-
 extensions/amp-vine/0.1/amp-vine.js                             | 2 +-
 extensions/amp-yotpo/0.1/amp-yotpo.js                           | 2 +-
 extensions/amp-youtube/1.0/amp-youtube.js                       | 2 +-
 src/action-constants.js                                         | 2 +-
 src/context/component-hooks.js                                  | 2 +-
 src/context/node.js                                             | 2 +-
 src/context/prop.js                                             | 2 +-
 src/cookies.js                                                  | 2 +-
 src/css.js                                                      | 2 +-
 src/element-service.js                                          | 2 +-
 src/extension-analytics.js                                      | 2 +-
 src/finite-state-machine.js                                     | 2 +-
 src/gesture.js                                                  | 2 +-
 src/modal.js                                                    | 2 +-
 src/preact/base-element.js                                      | 2 +-
 src/render-delaying-services.js                                 | 2 +-
 src/service/core-services.js                                    | 2 +-
 src/service/custom-element-registry.js                          | 2 +-
 src/service/hidden-observer-impl.js                             | 2 +-
 src/service/owners-impl.js                                      | 2 +-
 src/service/position-observer/position-observer-worker.js       | 2 +-
 src/service/task-queue.js                                       | 2 +-
 src/service/template-impl.js                                    | 2 +-
 src/service/variable-source.js                                  | 2 +-
 src/ssr-template-helper.js                                      | 2 +-
 src/static-template.js                                          | 2 +-
 src/url.js                                                      | 2 +-
 src/utils/bytes.js                                              | 2 +-
 src/utils/detached-dom-stream.js                                | 2 +-
 src/utils/math.js                                               | 2 +-
 src/viewport-observer.js                                        | 2 +-
 120 files changed, 120 insertions(+), 120 deletions(-)

diff --git a/3p/facebook.js b/3p/facebook.js
index 0590f15e693e..50e1067c3878 100644
--- a/3p/facebook.js
+++ b/3p/facebook.js
@@ -18,7 +18,7 @@ import {dashToUnderline} from '../src/string';
 import {dict} from '../src/utils/object';
 import {loadScript} from './3p';
 import {setStyle} from '../src/style';
-import {pureUserAssert as userAssert} from '../src/assert';
+import {pureUserAssert as userAssert} from '../src/core/assert';
 
 /**
  * Produces the Facebook SDK object for the passed in callback.
diff --git a/3p/github.js b/3p/github.js
index 7b697106be88..9fc2a7a6d676 100644
--- a/3p/github.js
+++ b/3p/github.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {pureUserAssert as userAssert} from '../src/assert';
+import {pureUserAssert as userAssert} from '../src/core/assert';
 import {writeScript} from './3p';
 
 /**
diff --git a/3p/mathml.js b/3p/mathml.js
index 23de90f355e1..db3da04e0869 100644
--- a/3p/mathml.js
+++ b/3p/mathml.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 import {setStyle} from '../src/style';
-import {pureUserAssert as userAssert} from '../src/assert';
+import {pureUserAssert as userAssert} from '../src/core/assert';
 import {writeScript} from './3p';
 
 /**
diff --git a/ads/vendors/csa.js b/ads/vendors/csa.js
index 3e9bb767219e..b6ea448bb04b 100644
--- a/ads/vendors/csa.js
+++ b/ads/vendors/csa.js
@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-import {pureDevAssert as devAssert} from '../../src/assert';
+import {pureDevAssert as devAssert} from '../../src/core/assert';
 import {getStyle, setStyle, setStyles} from '../../src/style';
 import {loadScript, validateData} from '../../3p/3p';
 import {tryParseJson} from '../../src/json.js';
diff --git a/build-system/tasks/extension-generator/bento/amp-__component_name_hyphenated__/__component_version__/amp-__component_name_hyphenated__.js b/build-system/tasks/extension-generator/bento/amp-__component_name_hyphenated__/__component_version__/amp-__component_name_hyphenated__.js
index 920ad6f2cfc1..46a71564afcc 100644
--- a/build-system/tasks/extension-generator/bento/amp-__component_name_hyphenated__/__component_version__/amp-__component_name_hyphenated__.js
+++ b/build-system/tasks/extension-generator/bento/amp-__component_name_hyphenated__/__component_version__/amp-__component_name_hyphenated__.js
@@ -18,7 +18,7 @@ import {BaseElement} from './base-element';
 import {CSS} from '../../../build/amp-__component_name_hyphenated__-__component_version__.css';
 import {dict} from '../../../src/utils/object';
 import {isExperimentOn} from '../../../src/experiments';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /** @const {string} */
 const TAG = 'amp-__component_name_hyphenated__';
diff --git a/contributing/building-a-bento-amp-extension.md b/contributing/building-a-bento-amp-extension.md
index bcd9a8eea92e..c0496228f824 100644
--- a/contributing/building-a-bento-amp-extension.md
+++ b/contributing/building-a-bento-amp-extension.md
@@ -484,7 +484,7 @@ Then protect your code with a check for the component-specific flag `isExperimen
 ```javascript
 import {CSS} from '../../../build/amp-my-element-0.1.css';
 import {isExperimentOn} from '../../../src/experiments';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /** @const */
 const TAG = 'amp-my-element';
diff --git a/contributing/building-an-amp-extension.md b/contributing/building-an-amp-extension.md
index 47d5141aee5a..4e9cac36bce8 100644
--- a/contributing/building-an-amp-extension.md
+++ b/contributing/building-an-amp-extension.md
@@ -659,7 +659,7 @@ And then protecting your code with a check `isExperimentOn(win, 'amp-my-element'
 
 ```javascript
 import {isExperimentOn} from '../../../src/experiments';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /** @const */
 const EXPERIMENT = 'amp-my-element';
diff --git a/extensions/amp-a4a/0.1/amp-ad-template-helper.js b/extensions/amp-a4a/0.1/amp-ad-template-helper.js
index ed3709b728e6..c71453034a58 100644
--- a/extensions/amp-a4a/0.1/amp-ad-template-helper.js
+++ b/extensions/amp-a4a/0.1/amp-ad-template-helper.js
@@ -17,7 +17,7 @@
 import {LruCache} from '../../../src/utils/lru-cache';
 import {Services} from '../../../src/services';
 import {createElementWithAttributes} from '../../../src/dom';
-import {pureDevAssert as devAssert} from '../../../src/assert';
+import {pureDevAssert as devAssert} from '../../../src/core/assert';
 import {dict} from '../../../src/utils/object';
 import {getMode} from '../../../src/mode';
 import {isArray} from '../../../src/types';
diff --git a/extensions/amp-a4a/0.1/friendly-frame-renderer.js b/extensions/amp-a4a/0.1/friendly-frame-renderer.js
index feeb893598de..197b417758d3 100644
--- a/extensions/amp-a4a/0.1/friendly-frame-renderer.js
+++ b/extensions/amp-a4a/0.1/friendly-frame-renderer.js
@@ -15,7 +15,7 @@
  */
 
 import {Renderer} from './amp-ad-type-defs';
-import {pureDevAssert as devAssert} from '../../../src/assert';
+import {pureDevAssert as devAssert} from '../../../src/core/assert';
 import {renderCreativeIntoFriendlyFrame} from './friendly-frame-util';
 
 /**
diff --git a/extensions/amp-a4a/0.1/template-renderer.js b/extensions/amp-a4a/0.1/template-renderer.js
index 16fae91a075a..2d84dd5cdd9e 100644
--- a/extensions/amp-a4a/0.1/template-renderer.js
+++ b/extensions/amp-a4a/0.1/template-renderer.js
@@ -15,7 +15,7 @@
  */
 
 import {Renderer} from './amp-ad-type-defs';
-import {puredevAssert as devAssert} from '../../../src/assert';
+import {pureDevAssert as devAssert} from '../../../src/core/assert';
 import {getAmpAdTemplateHelper} from './template-validator';
 import {renderCreativeIntoFriendlyFrame} from './friendly-frame-util';
 
diff --git a/extensions/amp-access-scroll/0.1/scroll-component.js b/extensions/amp-access-scroll/0.1/scroll-component.js
index e3f26e4a269a..160ae5a9958e 100644
--- a/extensions/amp-access-scroll/0.1/scroll-component.js
+++ b/extensions/amp-access-scroll/0.1/scroll-component.js
@@ -17,7 +17,7 @@
 import {Services} from '../../../src/services';
 import {assertDoesNotContainDisplay, px, setStyles} from '../../../src/style';
 import {createElementWithAttributes} from '../../../src/dom';
-import {pureDevAssert as devAssert} from '../../../src/assert';
+import {pureDevAssert as devAssert} from '../../../src/core/assert';
 import {hasOwn} from '../../../src/utils/object';
 
 /** @abstract */
diff --git a/extensions/amp-accordion/1.0/amp-accordion.js b/extensions/amp-accordion/1.0/amp-accordion.js
index db3a75cce999..3e7c190bba5f 100644
--- a/extensions/amp-accordion/1.0/amp-accordion.js
+++ b/extensions/amp-accordion/1.0/amp-accordion.js
@@ -21,7 +21,7 @@ import {Services} from '../../../src/services';
 import {createCustomEvent} from '../../../src/event-helper';
 import {isExperimentOn} from '../../../src/experiments';
 import {toWin} from '../../../src/types';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /** @const {string} */
 const TAG = 'amp-accordion';
diff --git a/extensions/amp-accordion/1.0/base-element.js b/extensions/amp-accordion/1.0/base-element.js
index 278386181065..1652bdf974bc 100644
--- a/extensions/amp-accordion/1.0/base-element.js
+++ b/extensions/amp-accordion/1.0/base-element.js
@@ -23,7 +23,7 @@ import {
 } from './component';
 import {PreactBaseElement} from '../../../src/preact/base-element';
 import {childElementsByTag, toggleAttribute} from '../../../src/dom';
-import {pureDevAssert as devAssert} from '../../../src/core/assert';
+import {pureDevAssert as devAssert} from '../../../src/core/core/assert';
 import {dict, memo} from '../../../src/utils/object';
 import {forwardRef} from '../../../src/preact/compat';
 import {toArray} from '../../../src/types';
diff --git a/extensions/amp-action-macro/0.1/amp-action-macro.js b/extensions/amp-action-macro/0.1/amp-action-macro.js
index bc8a4427dcbd..9080a669f78f 100644
--- a/extensions/amp-action-macro/0.1/amp-action-macro.js
+++ b/extensions/amp-action-macro/0.1/amp-action-macro.js
@@ -15,7 +15,7 @@
  */
 import {LayoutPriority} from '../../../src/layout';
 import {Services} from '../../../src/services';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /** @const {string} */
 const TAG = 'amp-action-macro';
diff --git a/extensions/amp-ad-custom/0.1/amp-ad-custom.js b/extensions/amp-ad-custom/0.1/amp-ad-custom.js
index 77a0086d4b85..ba143a72faff 100644
--- a/extensions/amp-ad-custom/0.1/amp-ad-custom.js
+++ b/extensions/amp-ad-custom/0.1/amp-ad-custom.js
@@ -24,7 +24,7 @@ import {Services} from '../../../src/services';
 import {TemplateRenderer} from '../../amp-a4a/0.1/template-renderer';
 import {TemplateValidator} from '../../amp-a4a/0.1/template-validator';
 import {addParamToUrl} from '../../../src/url';
-import {pureDevAssert as devAssert} from '../../../src/assert';
+import {pureDevAssert as devAssert} from '../../../src/core/assert';
 
 // These have no side-effects, and so may be reused between all instances.
 const validator = new TemplateValidator();
diff --git a/extensions/amp-ad-exit/0.1/filters/click-location.js b/extensions/amp-ad-exit/0.1/filters/click-location.js
index 3132d1807337..b9b4c4a018c7 100644
--- a/extensions/amp-ad-exit/0.1/filters/click-location.js
+++ b/extensions/amp-ad-exit/0.1/filters/click-location.js
@@ -15,7 +15,7 @@
  */
 
 import {Filter, FilterType} from './filter';
-import {pureUserAssert as userAssert} from '../../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../../src/core/assert';
 
 export class ClickLocationFilter extends Filter {
   /**
diff --git a/extensions/amp-ad-network-adsense-impl/0.1/adsense-shared-state.js b/extensions/amp-ad-network-adsense-impl/0.1/adsense-shared-state.js
index b38cd1da06e7..52643b6d36f6 100644
--- a/extensions/amp-ad-network-adsense-impl/0.1/adsense-shared-state.js
+++ b/extensions/amp-ad-network-adsense-impl/0.1/adsense-shared-state.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {pureDevAssert as devAssert} from '../../../src/assert';
+import {pureDevAssert as devAssert} from '../../../src/core/assert';
 
 /**
  * Maintains state in between different AdSense slots on the same page. This
diff --git a/extensions/amp-ad-network-doubleclick-impl/0.1/test/test-doubleclick-sra.js b/extensions/amp-ad-network-doubleclick-impl/0.1/test/test-doubleclick-sra.js
index 0c796bb776c1..df4f9c614971 100644
--- a/extensions/amp-ad-network-doubleclick-impl/0.1/test/test-doubleclick-sra.js
+++ b/extensions/amp-ad-network-doubleclick-impl/0.1/test/test-doubleclick-sra.js
@@ -50,7 +50,7 @@ import {
 } from '../sra-utils';
 import {Xhr} from '../../../../src/service/xhr-impl';
 import {createElementWithAttributes} from '../../../../src/dom';
-import {pureDevAssert as devAssert} from '../../../../src/assert';
+import {pureDevAssert as devAssert} from '../../../../src/core/assert';
 import {layoutRectLtwh} from '../../../../src/layout-rect';
 import {utf8Decode, utf8Encode} from '../../../../src/utils/bytes';
 
diff --git a/extensions/amp-ad/0.1/amp-ad-custom.js b/extensions/amp-ad/0.1/amp-ad-custom.js
index 82901e99cd83..dc12bf78c1bf 100644
--- a/extensions/amp-ad/0.1/amp-ad-custom.js
+++ b/extensions/amp-ad/0.1/amp-ad-custom.js
@@ -25,7 +25,7 @@ import {
   removeChildren,
 } from '../../../src/dom';
 import {hasOwn} from '../../../src/utils/object';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /** @const {string} Tag name for custom ad implementation. */
 export const TAG_AD_CUSTOM = 'amp-ad-custom';
diff --git a/extensions/amp-ad/0.1/amp-ad-ui.js b/extensions/amp-ad/0.1/amp-ad-ui.js
index 6b264171896e..1bef0c337ddb 100644
--- a/extensions/amp-ad/0.1/amp-ad-ui.js
+++ b/extensions/amp-ad/0.1/amp-ad-ui.js
@@ -24,7 +24,7 @@ import {
   createElementWithAttributes,
   removeElement,
 } from '../../../src/dom';
-import {pureDevAssert as devAssert} from '../../../src/assert';
+import {pureDevAssert as devAssert} from '../../../src/core/assert';
 import {dict} from '../../../src/utils/object';
 import {getExperimentBranch} from '../../../src/experiments';
 
diff --git a/extensions/amp-ad/0.1/amp-ad.js b/extensions/amp-ad/0.1/amp-ad.js
index 2c52e3a25433..d14b814e0f90 100644
--- a/extensions/amp-ad/0.1/amp-ad.js
+++ b/extensions/amp-ad/0.1/amp-ad.js
@@ -20,7 +20,7 @@ import {Services} from '../../../src/services';
 import {adConfig} from '../../../ads/_config';
 import {getA4ARegistry} from '../../../ads/_a4a-config';
 import {hasOwn} from '../../../src/utils/object';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /**
  * Construct ad network type-specific tag and script name.  Note that this
diff --git a/extensions/amp-addthis/0.1/amp-addthis.js b/extensions/amp-addthis/0.1/amp-addthis.js
index 717da8fd3291..bc63e848e39f 100644
--- a/extensions/amp-addthis/0.1/amp-addthis.js
+++ b/extensions/amp-addthis/0.1/amp-addthis.js
@@ -70,7 +70,7 @@ import {isLayoutSizeDefined} from '../../../src/layout';
 import {listen} from '../../../src/event-helper';
 import {parseUrlDeprecated} from '../../../src/url';
 import {setStyle} from '../../../src/style';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 // The following items will be shared by all AmpAddThis elements on a page, to
 // prevent unnecessary HTTP requests, get accurate analytics, etc., and hence
diff --git a/extensions/amp-analytics/0.1/scroll-manager.js b/extensions/amp-analytics/0.1/scroll-manager.js
index 92e7100ab850..42e0809bd1cb 100644
--- a/extensions/amp-analytics/0.1/scroll-manager.js
+++ b/extensions/amp-analytics/0.1/scroll-manager.js
@@ -16,7 +16,7 @@
 
 import {Observable} from '../../../src/observable';
 import {Services} from '../../../src/services';
-import {pureDevAssert as devAssert} from '../../../src/assert';
+import {pureDevAssert as devAssert} from '../../../src/core/assert';
 
 /**
  * @typedef {{
diff --git a/extensions/amp-analytics/0.1/visibility-model.js b/extensions/amp-analytics/0.1/visibility-model.js
index e038b40fb23b..f58ea3ab9e59 100644
--- a/extensions/amp-analytics/0.1/visibility-model.js
+++ b/extensions/amp-analytics/0.1/visibility-model.js
@@ -16,7 +16,7 @@
 
 import {Deferred} from '../../../src/utils/promise';
 import {Observable} from '../../../src/observable';
-import {pureDevAssert as devAssert} from '../../../src/assert';
+import {pureDevAssert as devAssert} from '../../../src/core/assert';
 import {dict} from '../../../src/utils/object';
 
 /**
diff --git a/extensions/amp-animation/0.1/runners/native-web-animation-runner.js b/extensions/amp-animation/0.1/runners/native-web-animation-runner.js
index e0172d33bd97..526639503c6c 100644
--- a/extensions/amp-animation/0.1/runners/native-web-animation-runner.js
+++ b/extensions/amp-animation/0.1/runners/native-web-animation-runner.js
@@ -29,7 +29,7 @@ import {
   WebSwitchAnimationDef,
 } from '../web-animation-types';
 import {assertDoesNotContainDisplay, setStyles} from '../../../../src/style';
-import {pureDevAssert as devAssert} from '../../../../src/assert';
+import {pureDevAssert as devAssert} from '../../../../src/core/assert';
 import {getTotalDuration} from './utils';
 
 /**
diff --git a/extensions/amp-animation/0.1/runners/utils.js b/extensions/amp-animation/0.1/runners/utils.js
index 18cbf914429b..60691a21d7bb 100644
--- a/extensions/amp-animation/0.1/runners/utils.js
+++ b/extensions/amp-animation/0.1/runners/utils.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {pureUserAssert as userAssert} from '../../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../../src/core/assert';
 
 /**
  * @param {!Array<!../web-animation-types.InternalWebAnimationRequestDef>} requests
diff --git a/extensions/amp-auto-ads/0.1/amp-auto-ads.js b/extensions/amp-auto-ads/0.1/amp-auto-ads.js
index 9f0f14e646a7..46b5e410533f 100644
--- a/extensions/amp-auto-ads/0.1/amp-auto-ads.js
+++ b/extensions/amp-auto-ads/0.1/amp-auto-ads.js
@@ -27,7 +27,7 @@ import {dict} from '../../../src/utils/object';
 import {getAdNetworkConfig} from './ad-network-config';
 import {getPlacementsFromConfigObj} from './placement';
 import {isExperimentOn} from '../../../src/experiments';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /** @const */
 const TAG = 'amp-auto-ads';
diff --git a/extensions/amp-autocomplete/0.1/autocomplete-binding-inline.js b/extensions/amp-autocomplete/0.1/autocomplete-binding-inline.js
index 2dd8689f8d75..a4fc8fb1a144 100644
--- a/extensions/amp-autocomplete/0.1/autocomplete-binding-inline.js
+++ b/extensions/amp-autocomplete/0.1/autocomplete-binding-inline.js
@@ -16,7 +16,7 @@
 
 import {ownProperty} from '../../../src/utils/object';
 import {tryFocus} from '../../../src/dom';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 const TAG = 'amp-autocomplete';
 
diff --git a/extensions/amp-base-carousel/1.0/amp-base-carousel.js b/extensions/amp-base-carousel/1.0/amp-base-carousel.js
index 3799c865d785..59b3e7a8f831 100644
--- a/extensions/amp-base-carousel/1.0/amp-base-carousel.js
+++ b/extensions/amp-base-carousel/1.0/amp-base-carousel.js
@@ -25,7 +25,7 @@ import {createCustomEvent} from '../../../src/event-helper';
 import {dict} from '../../../src/utils/object';
 import {dispatchCustomEvent} from '../../../src/dom';
 import {isExperimentOn} from '../../../src/experiments';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /** @const {string} */
 const TAG = 'amp-base-carousel';
diff --git a/extensions/amp-bodymovin-animation/0.1/amp-bodymovin-animation.js b/extensions/amp-bodymovin-animation/0.1/amp-bodymovin-animation.js
index 6b185409504e..a37dbc98f7c5 100644
--- a/extensions/amp-bodymovin-animation/0.1/amp-bodymovin-animation.js
+++ b/extensions/amp-bodymovin-animation/0.1/amp-bodymovin-animation.js
@@ -27,7 +27,7 @@ import {isFiniteNumber, isObject} from '../../../src/types';
 import {isLayoutSizeDefined} from '../../../src/layout';
 import {parseJson} from '../../../src/json';
 import {removeElement} from '../../../src/dom';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 const TAG = 'amp-bodymovin-animation';
 
diff --git a/extensions/amp-carousel/0.1/base-slides.js b/extensions/amp-carousel/0.1/base-slides.js
index f310eb041cbc..af7349903c0e 100644
--- a/extensions/amp-carousel/0.1/base-slides.js
+++ b/extensions/amp-carousel/0.1/base-slides.js
@@ -18,7 +18,7 @@ import {ActionTrust} from '../../../src/action-constants';
 import {BaseCarousel} from './base-carousel';
 import {Services} from '../../../src/services';
 import {isFiniteNumber} from '../../../src/types';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 export class BaseSlides extends BaseCarousel {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-connatix-player/0.1/amp-connatix-player.js b/extensions/amp-connatix-player/0.1/amp-connatix-player.js
index dd0347df1240..2db565329400 100644
--- a/extensions/amp-connatix-player/0.1/amp-connatix-player.js
+++ b/extensions/amp-connatix-player/0.1/amp-connatix-player.js
@@ -37,7 +37,7 @@ import {
 import {removeElement} from '../../../src/dom';
 import {setIsMediaComponent} from '../../../src/video-interface';
 import {tryParseJson} from '../../../src/json';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /**
  * @param {!Array<T>} promises
diff --git a/extensions/amp-delight-player/0.1/amp-delight-player.js b/extensions/amp-delight-player/0.1/amp-delight-player.js
index f1ce7d0eafd2..b339ebcc0e4a 100644
--- a/extensions/amp-delight-player/0.1/amp-delight-player.js
+++ b/extensions/amp-delight-player/0.1/amp-delight-player.js
@@ -40,7 +40,7 @@ import {
   unobserveWithSharedInOb,
 } from '../../../src/viewport-observer';
 import {setStyle} from '../../../src/style';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /** @const */
 const TAG = 'amp-delight-player';
diff --git a/extensions/amp-embedly-card/0.1/amp-embedly-card-impl.js b/extensions/amp-embedly-card/0.1/amp-embedly-card-impl.js
index 4c447fe2a57d..b0debeb212cd 100644
--- a/extensions/amp-embedly-card/0.1/amp-embedly-card-impl.js
+++ b/extensions/amp-embedly-card/0.1/amp-embedly-card-impl.js
@@ -20,7 +20,7 @@ import {Services} from '../../../src/services';
 import {getIframe} from '../../../src/3p-frame';
 import {listenFor} from '../../../src/iframe-helper';
 import {removeElement} from '../../../src/dom';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /**
  * Component tag identifier.
diff --git a/extensions/amp-embedly-card/0.1/amp-embedly-key.js b/extensions/amp-embedly-card/0.1/amp-embedly-key.js
index b043ab7c4eba..342d6cb9a27b 100644
--- a/extensions/amp-embedly-card/0.1/amp-embedly-key.js
+++ b/extensions/amp-embedly-card/0.1/amp-embedly-key.js
@@ -15,7 +15,7 @@
  */
 
 import {Layout} from '../../../src/layout';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /** @const {string} */
 export const TAG = 'amp-embedly-key';
diff --git a/extensions/amp-experiment/1.0/mutation-record.js b/extensions/amp-experiment/1.0/mutation-record.js
index a86add188e46..5c289a40d05c 100644
--- a/extensions/amp-experiment/1.0/mutation-record.js
+++ b/extensions/amp-experiment/1.0/mutation-record.js
@@ -15,7 +15,7 @@
  */
 
 import {isObject, toArray} from '../../../src/types';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /**
  * Types of possibile mutations
diff --git a/extensions/amp-experiment/1.0/mutation/mutation.js b/extensions/amp-experiment/1.0/mutation/mutation.js
index 48f23ce298b1..38856b3dc6ed 100644
--- a/extensions/amp-experiment/1.0/mutation/mutation.js
+++ b/extensions/amp-experiment/1.0/mutation/mutation.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {pureUserAssert as userAssert} from '../../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../../src/core/assert';
 
 /**
  * Interface for amp-experiment mutations.
diff --git a/extensions/amp-fit-text/1.0/amp-fit-text.js b/extensions/amp-fit-text/1.0/amp-fit-text.js
index cec470bd08cc..788867cf0d32 100644
--- a/extensions/amp-fit-text/1.0/amp-fit-text.js
+++ b/extensions/amp-fit-text/1.0/amp-fit-text.js
@@ -17,7 +17,7 @@
 import {BaseElement} from './base-element';
 import {CSS} from '../../../build/amp-fit-text-1.0.css';
 import {isExperimentOn} from '../../../src/experiments';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /** @const {string} */
 const TAG = 'amp-fit-text';
diff --git a/extensions/amp-fx-collection/0.1/providers/amp-fx-presets-utils.js b/extensions/amp-fx-collection/0.1/providers/amp-fx-presets-utils.js
index 025038b83dda..e7224b4dfa92 100644
--- a/extensions/amp-fx-collection/0.1/providers/amp-fx-presets-utils.js
+++ b/extensions/amp-fx-collection/0.1/providers/amp-fx-presets-utils.js
@@ -22,7 +22,7 @@
 import {FxType} from '../fx-type';
 import {Services} from '../../../../src/services';
 import {mapRange} from '../../../../src/utils/math';
-import {pureUserAssert as userAssert} from '../../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../../src/core/assert';
 
 const MAX_MOBILE_WIDTH = 480;
 const MAX_TABLET_WIDTH = 1000;
diff --git a/extensions/amp-fx-collection/0.1/providers/fx-provider.js b/extensions/amp-fx-collection/0.1/providers/fx-provider.js
index a009d1d9a934..e4168cbb6a5b 100644
--- a/extensions/amp-fx-collection/0.1/providers/fx-provider.js
+++ b/extensions/amp-fx-collection/0.1/providers/fx-provider.js
@@ -41,7 +41,7 @@ import {
   installStyles,
   resolvePercentageToNumber,
 } from './amp-fx-presets-utils';
-import {pureDevAssert as devAssert} from '../../../../src/assert';
+import {pureDevAssert as devAssert} from '../../../../src/core/assert';
 import {
   getServiceForDoc,
   registerServiceBuilderForDoc,
diff --git a/extensions/amp-gwd-animation/0.1/amp-gwd-animation.js b/extensions/amp-gwd-animation/0.1/amp-gwd-animation.js
index 5faf41ba72e0..7f29821f5713 100644
--- a/extensions/amp-gwd-animation/0.1/amp-gwd-animation.js
+++ b/extensions/amp-gwd-animation/0.1/amp-gwd-animation.js
@@ -27,7 +27,7 @@ import {
   getParentWindowFrameElement,
   getServiceForDocOrNull,
 } from '../../../src/service';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /**
  * Returns a value at any level in an object structure addressed by dot-notation
diff --git a/extensions/amp-imgur/0.1/amp-imgur.js b/extensions/amp-imgur/0.1/amp-imgur.js
index e685df5d52b7..e237e8cfbb6e 100644
--- a/extensions/amp-imgur/0.1/amp-imgur.js
+++ b/extensions/amp-imgur/0.1/amp-imgur.js
@@ -32,7 +32,7 @@ import {isLayoutSizeDefined} from '../../../src/layout';
 import {isObject} from '../../../src/types';
 import {removeElement} from '../../../src/dom';
 import {tryParseJson} from '../../../src/json';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 export class AmpImgur extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-inline-gallery/0.1/amp-inline-gallery-pagination.js b/extensions/amp-inline-gallery/0.1/amp-inline-gallery-pagination.js
index 7823b44964ea..ad3725086214 100644
--- a/extensions/amp-inline-gallery/0.1/amp-inline-gallery-pagination.js
+++ b/extensions/amp-inline-gallery/0.1/amp-inline-gallery-pagination.js
@@ -17,7 +17,7 @@
 import {InlineGalleryEvents} from './inline-gallery-events';
 import {Layout} from '../../../src/layout';
 import {createCustomEvent} from '../../../src/event-helper';
-import {pureDevAssert as devAssert} from '../../../src/assert';
+import {pureDevAssert as devAssert} from '../../../src/core/assert';
 import {dict} from '../../../src/utils/object';
 import {htmlFor} from '../../../src/static-template';
 import {scopedQuerySelectorAll} from '../../../src/dom';
diff --git a/extensions/amp-inline-gallery/1.0/amp-inline-gallery-pagination.js b/extensions/amp-inline-gallery/1.0/amp-inline-gallery-pagination.js
index d9ca19665fdd..d77c75e2a6e4 100644
--- a/extensions/amp-inline-gallery/1.0/amp-inline-gallery-pagination.js
+++ b/extensions/amp-inline-gallery/1.0/amp-inline-gallery-pagination.js
@@ -19,7 +19,7 @@ import {CarouselContextProp} from '../../amp-base-carousel/1.0/carousel-props';
 import {Pagination} from './pagination';
 import {PreactBaseElement} from '../../../src/preact/base-element';
 import {isExperimentOn} from '../../../src/experiments';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /** @const {string} */
 export const TAG = 'amp-inline-gallery-pagination';
diff --git a/extensions/amp-inline-gallery/1.0/amp-inline-gallery-thumbnails.js b/extensions/amp-inline-gallery/1.0/amp-inline-gallery-thumbnails.js
index 863fbda4201e..09c67bdd0d45 100644
--- a/extensions/amp-inline-gallery/1.0/amp-inline-gallery-thumbnails.js
+++ b/extensions/amp-inline-gallery/1.0/amp-inline-gallery-thumbnails.js
@@ -20,7 +20,7 @@ import {PreactBaseElement} from '../../../src/preact/base-element';
 import {CSS as THUMBNAIL_CSS} from './thumbnails.jss';
 import {Thumbnails} from './thumbnails';
 import {isExperimentOn} from '../../../src/experiments';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /** @const {string} */
 export const TAG = 'amp-inline-gallery-thumbnails';
diff --git a/extensions/amp-inline-gallery/1.0/amp-inline-gallery.js b/extensions/amp-inline-gallery/1.0/amp-inline-gallery.js
index cf0368f1d5ea..fd5a8eba88bb 100644
--- a/extensions/amp-inline-gallery/1.0/amp-inline-gallery.js
+++ b/extensions/amp-inline-gallery/1.0/amp-inline-gallery.js
@@ -32,7 +32,7 @@ import {dict} from '../../../src/utils/object';
 import {isExperimentOn} from '../../../src/experiments';
 import {setProp} from '../../../src/context';
 import {useContext, useLayoutEffect} from '../../../src/preact';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /** @const {string} */
 const TAG = 'amp-inline-gallery';
diff --git a/extensions/amp-inputmask/0.1/text-mask.js b/extensions/amp-inputmask/0.1/text-mask.js
index c9d72fb1712c..4ed28b829f63 100644
--- a/extensions/amp-inputmask/0.1/text-mask.js
+++ b/extensions/amp-inputmask/0.1/text-mask.js
@@ -18,7 +18,7 @@ import {Mask} from './mask-impl';
 import {OutputMode} from './constants';
 import {Services} from '../../../src/services';
 import {iterateCursor, removeElement} from '../../../src/dom';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 const ELEMENT_MASK_PROPERTY = '__amp_inputmask_masked';
 const ELEMENT_MASK_OUTPUT_PROPERTY = '__amp_inputmask_hidden';
diff --git a/extensions/amp-instagram/0.1/amp-instagram.js b/extensions/amp-instagram/0.1/amp-instagram.js
index 5b8b19fc2c0a..6e191c5736b6 100644
--- a/extensions/amp-instagram/0.1/amp-instagram.js
+++ b/extensions/amp-instagram/0.1/amp-instagram.js
@@ -43,7 +43,7 @@ import {isObject} from '../../../src/types';
 import {removeElement} from '../../../src/dom';
 import {setStyle} from '../../../src/style';
 import {tryParseJson} from '../../../src/json';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 export class AmpInstagram extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-instagram/1.0/amp-instagram.js b/extensions/amp-instagram/1.0/amp-instagram.js
index c14fa53c880b..7b491259782d 100644
--- a/extensions/amp-instagram/1.0/amp-instagram.js
+++ b/extensions/amp-instagram/1.0/amp-instagram.js
@@ -18,7 +18,7 @@ import {BaseElement} from './base-element';
 import {CSS} from '../../../build/amp-instagram-1.0.css';
 import {dict} from '../../../src/utils/object';
 import {isExperimentOn} from '../../../src/experiments';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /** @const {string} */
 const TAG = 'amp-instagram';
diff --git a/extensions/amp-kaltura-player/0.1/amp-kaltura-player.js b/extensions/amp-kaltura-player/0.1/amp-kaltura-player.js
index b34d28716654..8e68dca6d52f 100644
--- a/extensions/amp-kaltura-player/0.1/amp-kaltura-player.js
+++ b/extensions/amp-kaltura-player/0.1/amp-kaltura-player.js
@@ -20,7 +20,7 @@ import {dict} from '../../../src/utils/object';
 import {getDataParamsFromAttributes} from '../../../src/dom';
 import {isLayoutSizeDefined} from '../../../src/layout';
 import {setIsMediaComponent} from '../../../src/video-interface';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 class AmpKaltura extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-lightbox-gallery/0.1/lightbox-controls.js b/extensions/amp-lightbox-gallery/0.1/lightbox-controls.js
index 12ba4354fedf..ba4df5d7693f 100644
--- a/extensions/amp-lightbox-gallery/0.1/lightbox-controls.js
+++ b/extensions/amp-lightbox-gallery/0.1/lightbox-controls.js
@@ -16,7 +16,7 @@
 
 import {Services} from '../../../src/services';
 import {createCustomEvent} from '../../../src/event-helper';
-import {pureDevAssert as devAssert} from '../../../src/assert';
+import {pureDevAssert as devAssert} from '../../../src/core/assert';
 import {dict} from '../../../src/utils/object';
 import {htmlFor} from '../../../src/static-template';
 import {toArray} from '../../../src/types';
diff --git a/extensions/amp-lightbox/1.0/amp-lightbox.js b/extensions/amp-lightbox/1.0/amp-lightbox.js
index 2685d638a910..4cd60e0370b1 100644
--- a/extensions/amp-lightbox/1.0/amp-lightbox.js
+++ b/extensions/amp-lightbox/1.0/amp-lightbox.js
@@ -21,7 +21,7 @@ import {Services} from '../../../src/services';
 import {createCustomEvent} from '../../../src/event-helper';
 import {isExperimentOn} from '../../../src/experiments';
 import {toWin} from '../../../src/types';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /** @const {string} */
 const TAG = 'amp-lightbox';
diff --git a/extensions/amp-live-list/0.1/live-list-manager.js b/extensions/amp-live-list/0.1/live-list-manager.js
index 8d7ee299eb56..6303bba05544 100644
--- a/extensions/amp-live-list/0.1/live-list-manager.js
+++ b/extensions/amp-live-list/0.1/live-list-manager.js
@@ -21,7 +21,7 @@ import {fetchDocument} from '../../../src/document-fetcher';
 import {getMode} from '../../../src/mode';
 import {getServicePromiseForDoc} from '../../../src/service';
 import {toArray} from '../../../src/types';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /** @const {string} */
 export const SERVICE_ID = 'liveListManager';
diff --git a/extensions/amp-megaphone/0.1/amp-megaphone.js b/extensions/amp-megaphone/0.1/amp-megaphone.js
index 426be01447be..eca3d890ca17 100644
--- a/extensions/amp-megaphone/0.1/amp-megaphone.js
+++ b/extensions/amp-megaphone/0.1/amp-megaphone.js
@@ -36,7 +36,7 @@ import {isObject} from '../../../src/types';
 import {removeElement} from '../../../src/dom';
 import {setIsMediaComponent} from '../../../src/video-interface';
 import {tryParseJson} from '../../../src/json';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 class AmpMegaphone extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-next-page/1.0/page.js b/extensions/amp-next-page/1.0/page.js
index e39c558ffd6f..4639bed79b6f 100644
--- a/extensions/amp-next-page/1.0/page.js
+++ b/extensions/amp-next-page/1.0/page.js
@@ -16,7 +16,7 @@
 
 import {ViewportRelativePos} from './visibility-observer';
 import {VisibilityState} from '../../../src/visibility-state';
-import {pureDevAssert as devAssert} from '../../../src/assert';
+import {pureDevAssert as devAssert} from '../../../src/core/assert';
 
 /** @enum {number} */
 export const PageState = {
diff --git a/extensions/amp-next-page/1.0/visibility-observer.js b/extensions/amp-next-page/1.0/visibility-observer.js
index c35ea56d4b0a..232207355eb9 100644
--- a/extensions/amp-next-page/1.0/visibility-observer.js
+++ b/extensions/amp-next-page/1.0/visibility-observer.js
@@ -24,7 +24,7 @@ import {
 } from '../../../src/service/position-observer/position-observer-impl';
 import {RelativePositions} from '../../../src/layout-rect';
 import {Services} from '../../../src/services';
-import {pureDevAssert as devAssert} from '../../../src/assert';
+import {pureDevAssert as devAssert} from '../../../src/core/assert';
 import {throttle} from '../../../src/utils/rate-limit';
 
 /** @enum {number} */
diff --git a/extensions/amp-o2-player/0.1/amp-o2-player.js b/extensions/amp-o2-player/0.1/amp-o2-player.js
index 6a73261f09f0..3b6238a812fb 100644
--- a/extensions/amp-o2-player/0.1/amp-o2-player.js
+++ b/extensions/amp-o2-player/0.1/amp-o2-player.js
@@ -25,7 +25,7 @@ import {
 import {isLayoutSizeDefined} from '../../../src/layout';
 import {listenFor} from '../../../src/iframe-helper';
 import {setIsMediaComponent} from '../../../src/video-interface';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 class AmpO2Player extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-orientation-observer/0.1/amp-orientation-observer.js b/extensions/amp-orientation-observer/0.1/amp-orientation-observer.js
index 5a847c41eb8d..a61da07facca 100644
--- a/extensions/amp-orientation-observer/0.1/amp-orientation-observer.js
+++ b/extensions/amp-orientation-observer/0.1/amp-orientation-observer.js
@@ -19,7 +19,7 @@ import {Services} from '../../../src/services';
 import {clamp, sum} from '../../../src/utils/math';
 import {createCustomEvent} from '../../../src/event-helper';
 import {dict} from '../../../src/utils/object';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 const TAG = 'amp-orientation-observer';
 /**
diff --git a/extensions/amp-pinterest/0.1/follow-button.js b/extensions/amp-pinterest/0.1/follow-button.js
index ae852e1f803b..98f7263b4f38 100644
--- a/extensions/amp-pinterest/0.1/follow-button.js
+++ b/extensions/amp-pinterest/0.1/follow-button.js
@@ -19,7 +19,7 @@ import {assertHttpsUrl} from '../../../src/url';
 import {openWindowDialog} from '../../../src/dom';
 import {tryResolve} from '../../../src/utils/promise';
 
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 // Popup options
 const POP_FOLLOW = `status=no,resizable=yes,scrollbars=yes,
diff --git a/extensions/amp-recaptcha-input/0.1/amp-recaptcha-input.js b/extensions/amp-recaptcha-input/0.1/amp-recaptcha-input.js
index dd4fcd1a85da..68d87ee86a7e 100644
--- a/extensions/amp-recaptcha-input/0.1/amp-recaptcha-input.js
+++ b/extensions/amp-recaptcha-input/0.1/amp-recaptcha-input.js
@@ -31,7 +31,7 @@ import {
 import {CSS} from '../../../build/amp-recaptcha-input-0.1.css';
 import {Layout} from '../../../src/layout';
 import {setStyles, toggle} from '../../../src/style';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /** @const */
 const TAG = 'amp-recaptcha-input';
diff --git a/extensions/amp-redbull-player/0.1/amp-redbull-player.js b/extensions/amp-redbull-player/0.1/amp-redbull-player.js
index 740ccdd34499..72ba27c0ced9 100644
--- a/extensions/amp-redbull-player/0.1/amp-redbull-player.js
+++ b/extensions/amp-redbull-player/0.1/amp-redbull-player.js
@@ -33,7 +33,7 @@ import {
 import {getData, listen} from '../../../src/event-helper';
 import {installVideoManagerForDoc} from '../../../src/service/video-manager-impl';
 import {isLayoutSizeDefined} from '../../../src/layout';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /** @private @const */
 const TAG = 'amp-redbull-player';
diff --git a/extensions/amp-reddit/0.1/amp-reddit.js b/extensions/amp-reddit/0.1/amp-reddit.js
index f9f281bf6337..f22fa142a969 100644
--- a/extensions/amp-reddit/0.1/amp-reddit.js
+++ b/extensions/amp-reddit/0.1/amp-reddit.js
@@ -18,7 +18,7 @@ import {Services} from '../../../src/services';
 import {getIframe, preloadBootstrap} from '../../../src/3p-frame';
 import {isLayoutSizeDefined} from '../../../src/layout';
 import {listenFor} from '../../../src/iframe-helper';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 class AmpReddit extends AMP.BaseElement {
   /**
diff --git a/extensions/amp-riddle-quiz/0.1/amp-riddle-quiz.js b/extensions/amp-riddle-quiz/0.1/amp-riddle-quiz.js
index 8a97e9b94906..99c449e2711a 100644
--- a/extensions/amp-riddle-quiz/0.1/amp-riddle-quiz.js
+++ b/extensions/amp-riddle-quiz/0.1/amp-riddle-quiz.js
@@ -17,7 +17,7 @@ import {getData, listen} from './../../../src/event-helper';
 import {isFiniteNumber, isObject} from '../../../src/types';
 import {isLayoutSizeDefined} from '../../../src/layout';
 import {removeElement} from '../../../src/dom';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 export class AmpRiddleQuiz extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-selector/1.0/amp-selector.js b/extensions/amp-selector/1.0/amp-selector.js
index 18822bbc7af2..e1e5bf4c3904 100644
--- a/extensions/amp-selector/1.0/amp-selector.js
+++ b/extensions/amp-selector/1.0/amp-selector.js
@@ -22,7 +22,7 @@ import {createCustomEvent} from '../../../src/event-helper';
 import {dict} from '../../../src/utils/object';
 import {isExperimentOn} from '../../../src/experiments';
 import {toWin} from '../../../src/types';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /** @const {string} */
 const TAG = 'amp-selector';
diff --git a/extensions/amp-selector/1.0/base-element.js b/extensions/amp-selector/1.0/base-element.js
index 01dfba651546..27caa3a1999f 100644
--- a/extensions/amp-selector/1.0/base-element.js
+++ b/extensions/amp-selector/1.0/base-element.js
@@ -23,7 +23,7 @@ import {
   toggleAttribute,
   tryFocus,
 } from '../../../src/dom';
-import {pureDevAssert as devAssert} from '../../../src/core/assert';
+import {pureDevAssert as devAssert} from '../../../src/core/core/assert';
 import {dict} from '../../../src/utils/object';
 import {toArray} from '../../../src/types';
 import {useCallback, useLayoutEffect, useRef} from '../../../src/preact';
diff --git a/extensions/amp-sidebar/1.0/amp-sidebar.js b/extensions/amp-sidebar/1.0/amp-sidebar.js
index 26a63073497a..f47d64882fe0 100644
--- a/extensions/amp-sidebar/1.0/amp-sidebar.js
+++ b/extensions/amp-sidebar/1.0/amp-sidebar.js
@@ -21,7 +21,7 @@ import {Sidebar} from './sidebar';
 import {dict} from '../../../src/utils/object';
 import {isExperimentOn} from '../../../src/experiments';
 import {toggle} from '../../../src/style';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /** @const {string} */
 const TAG = 'amp-sidebar';
diff --git a/extensions/amp-skimlinks/0.1/link-rewriter/link-rewriter.js b/extensions/amp-skimlinks/0.1/link-rewriter/link-rewriter.js
index 3a5beae5fd8e..0c31db424242 100644
--- a/extensions/amp-skimlinks/0.1/link-rewriter/link-rewriter.js
+++ b/extensions/amp-skimlinks/0.1/link-rewriter/link-rewriter.js
@@ -19,7 +19,7 @@ import {EVENTS, ORIGINAL_URL_ATTRIBUTE} from './constants';
 import {LinkReplacementCache} from './link-replacement-cache';
 import {Observable} from '../../../../src/observable';
 import {TwoStepsResponse} from './two-steps-response';
-import {pureUserAssert as userAssert} from '../../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../../src/core/assert';
 
 /** @typedef {!Array<{anchor: !HTMLElement, replacementUrl: ?string}>}} */
 export let AnchorReplacementList;
diff --git a/extensions/amp-skimlinks/0.1/skim-options.js b/extensions/amp-skimlinks/0.1/skim-options.js
index 84ff78d4b453..2d94361e549d 100644
--- a/extensions/amp-skimlinks/0.1/skim-options.js
+++ b/extensions/amp-skimlinks/0.1/skim-options.js
@@ -16,7 +16,7 @@
 
 import {getChildJsonConfig} from '../../../src/json';
 import {getNormalizedHostnameFromUrl} from './utils';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 import {
   DEFAULT_CONFIG,
diff --git a/extensions/amp-social-share/1.0/amp-social-share.js b/extensions/amp-social-share/1.0/amp-social-share.js
index 9e81e06be343..9d923efd7ac5 100644
--- a/extensions/amp-social-share/1.0/amp-social-share.js
+++ b/extensions/amp-social-share/1.0/amp-social-share.js
@@ -26,7 +26,7 @@ import {getSocialConfig} from './social-share-config';
 import {isExperimentOn} from '../../../src/experiments';
 import {toWin} from '../../../src/types';
 import {toggle} from '../../../src/style';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /** @const {string} */
 const TAG = 'amp-social-share';
diff --git a/extensions/amp-soundcloud/0.1/amp-soundcloud.js b/extensions/amp-soundcloud/0.1/amp-soundcloud.js
index 4ca42ca338db..a11e87e42c2c 100644
--- a/extensions/amp-soundcloud/0.1/amp-soundcloud.js
+++ b/extensions/amp-soundcloud/0.1/amp-soundcloud.js
@@ -31,7 +31,7 @@ import {Services} from '../../../src/services';
 import {dict} from '../../../src/utils/object';
 import {isLayoutSizeDefined} from '../../../src/layout';
 import {setIsMediaComponent} from '../../../src/video-interface';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 class AmpSoundcloud extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-springboard-player/0.1/amp-springboard-player.js b/extensions/amp-springboard-player/0.1/amp-springboard-player.js
index 1c7eefcd90a9..783cd465fbb9 100644
--- a/extensions/amp-springboard-player/0.1/amp-springboard-player.js
+++ b/extensions/amp-springboard-player/0.1/amp-springboard-player.js
@@ -17,7 +17,7 @@
 import {Services} from '../../../src/services';
 import {isLayoutSizeDefined} from '../../../src/layout';
 import {setIsMediaComponent} from '../../../src/video-interface';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 class AmpSpringboardPlayer extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-story-auto-analytics/0.1/amp-story-auto-analytics.js b/extensions/amp-story-auto-analytics/0.1/amp-story-auto-analytics.js
index 3306e3baca0d..0bb6695e246f 100644
--- a/extensions/amp-story-auto-analytics/0.1/amp-story-auto-analytics.js
+++ b/extensions/amp-story-auto-analytics/0.1/amp-story-auto-analytics.js
@@ -16,7 +16,7 @@
 
 import {Services} from '../../../src/services';
 import {buildGtagConfig} from './auto-analytics-configs.js';
-import {pureDevAssert as devAssert} from '../../../src/assert';
+import {pureDevAssert as devAssert} from '../../../src/core/assert';
 import {htmlFor} from '../../../src/static-template';
 
 const buildAutoAnalyticsTemplate = (element) => {
diff --git a/extensions/amp-story/1.0/animation-presets.js b/extensions/amp-story/1.0/animation-presets.js
index 1babbb8e21f4..7e426fef60d4 100644
--- a/extensions/amp-story/1.0/animation-presets.js
+++ b/extensions/amp-story/1.0/animation-presets.js
@@ -24,7 +24,7 @@ import {
   whooshIn,
 } from './animation-presets-utils';
 import {px} from '../../../src/style';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /** @const {string} */
 const FULL_BLEED_CATEGORY = 'full-bleed';
diff --git a/extensions/amp-story/1.0/bookend/components/article.js b/extensions/amp-story/1.0/bookend/components/article.js
index 9e43259cc636..2ba93a58fd4a 100644
--- a/extensions/amp-story/1.0/bookend/components/article.js
+++ b/extensions/amp-story/1.0/bookend/components/article.js
@@ -28,7 +28,7 @@ import {
 } from '../../utils';
 import {getSourceUrl, resolveRelativeUrl} from '../../../../../src/url';
 import {htmlFor, htmlRefs} from '../../../../../src/static-template';
-import {pureUserAssert as userAssert} from '../../../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../../../src/core/assert';
 
 /**
  * @typedef {{
diff --git a/extensions/amp-story/1.0/bookend/components/cta-link.js b/extensions/amp-story/1.0/bookend/components/cta-link.js
index 49c59dc66e31..8d4f0e5154d2 100644
--- a/extensions/amp-story/1.0/bookend/components/cta-link.js
+++ b/extensions/amp-story/1.0/bookend/components/cta-link.js
@@ -24,7 +24,7 @@ import {dict} from '../../../../../src/utils/object';
 import {getSourceUrl, resolveRelativeUrl} from '../../../../../src/url';
 import {htmlFor, htmlRefs} from '../../../../../src/static-template';
 import {isArray} from '../../../../../src/types';
-import {pureUserAssert as userAssert} from '../../../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../../../src/core/assert';
 import {userAssertValidProtocol} from '../../utils';
 
 /**
diff --git a/extensions/amp-story/1.0/bookend/components/heading.js b/extensions/amp-story/1.0/bookend/components/heading.js
index fd777d14397f..ce7a9cb6a834 100644
--- a/extensions/amp-story/1.0/bookend/components/heading.js
+++ b/extensions/amp-story/1.0/bookend/components/heading.js
@@ -20,7 +20,7 @@ import {
   BookendComponentInterface,
 } from './bookend-component-interface';
 import {htmlFor} from '../../../../../src/static-template';
-import {pureUserAssert as userAssert} from '../../../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../../../src/core/assert';
 
 /**
  * @typedef {{
diff --git a/extensions/amp-story/1.0/bookend/components/landscape.js b/extensions/amp-story/1.0/bookend/components/landscape.js
index b9fe162f8a91..056714b38834 100644
--- a/extensions/amp-story/1.0/bookend/components/landscape.js
+++ b/extensions/amp-story/1.0/bookend/components/landscape.js
@@ -28,7 +28,7 @@ import {
 } from '../../utils';
 import {getSourceUrl, resolveRelativeUrl} from '../../../../../src/url';
 import {htmlFor, htmlRefs} from '../../../../../src/static-template';
-import {pureUserAssert as userAssert} from '../../../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../../../src/core/assert';
 
 /**
  * @typedef {{
diff --git a/extensions/amp-story/1.0/bookend/components/portrait.js b/extensions/amp-story/1.0/bookend/components/portrait.js
index d8be6ee1b0d7..31da5e662576 100644
--- a/extensions/amp-story/1.0/bookend/components/portrait.js
+++ b/extensions/amp-story/1.0/bookend/components/portrait.js
@@ -28,7 +28,7 @@ import {
 } from '../../utils';
 import {getSourceUrl, resolveRelativeUrl} from '../../../../../src/url';
 import {htmlFor, htmlRefs} from '../../../../../src/static-template';
-import {pureUserAssert as userAssert} from '../../../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../../../src/core/assert';
 
 /**
  * @typedef {{
diff --git a/extensions/amp-story/1.0/bookend/components/text-box.js b/extensions/amp-story/1.0/bookend/components/text-box.js
index 4e576579d106..55606ff4fd64 100644
--- a/extensions/amp-story/1.0/bookend/components/text-box.js
+++ b/extensions/amp-story/1.0/bookend/components/text-box.js
@@ -21,7 +21,7 @@ import {
 } from './bookend-component-interface';
 import {htmlFor} from '../../../../../src/static-template';
 import {isArray} from '../../../../../src/types';
-import {pureUserAssert as userAssert} from '../../../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../../../src/core/assert';
 
 /**
  * @typedef {{
diff --git a/extensions/amp-story/1.0/live-story-manager.js b/extensions/amp-story/1.0/live-story-manager.js
index 52425294ee79..6526463fa137 100644
--- a/extensions/amp-story/1.0/live-story-manager.js
+++ b/extensions/amp-story/1.0/live-story-manager.js
@@ -19,7 +19,7 @@ import {CommonSignals} from '../../../src/common-signals';
 import {Services} from '../../../src/services';
 import {createElementWithAttributes, lastChildElement} from '../../../src/dom';
 import {dict} from '../../../src/utils/object';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /**
  * Property used for storing id of custom slot. This custom slot can be used to
diff --git a/extensions/amp-story/1.0/pagination-buttons.js b/extensions/amp-story/1.0/pagination-buttons.js
index 6eea2756b2ca..877f0c34f9f8 100644
--- a/extensions/amp-story/1.0/pagination-buttons.js
+++ b/extensions/amp-story/1.0/pagination-buttons.js
@@ -24,7 +24,7 @@ import {CommonSignals} from '../../../src/common-signals';
 import {EventType, dispatch} from './events';
 import {Services} from '../../../src/services';
 import {dev} from '../../../src/log';
-import {pureDevAssert as devAssert} from '../../../src/assert';
+import {pureDevAssert as devAssert} from '../../../src/core/assert';
 import {htmlFor} from '../../../src/static-template';
 
 /** @struct @typedef {{className: string, triggers: (string|undefined)}} */
diff --git a/extensions/amp-story/1.0/simple-template.js b/extensions/amp-story/1.0/simple-template.js
index 62fcd9619946..45aabd19fac5 100644
--- a/extensions/amp-story/1.0/simple-template.js
+++ b/extensions/amp-story/1.0/simple-template.js
@@ -15,7 +15,7 @@
  */
 import {LocalizedStringId} from '../../../src/localized-strings'; // eslint-disable-line no-unused-vars
 import {createElementWithAttributes} from '../../../src/dom';
-import {pureDevAssert as devAssert} from '../../../src/assert';
+import {pureDevAssert as devAssert} from '../../../src/core/assert';
 import {getLocalizationService} from './amp-story-localization-service';
 import {hasOwn} from '../../../src/utils/object';
 import {isArray} from '../../../src/types';
diff --git a/extensions/amp-stream-gallery/1.0/amp-stream-gallery.js b/extensions/amp-stream-gallery/1.0/amp-stream-gallery.js
index c363b3525204..82825ae68000 100644
--- a/extensions/amp-stream-gallery/1.0/amp-stream-gallery.js
+++ b/extensions/amp-stream-gallery/1.0/amp-stream-gallery.js
@@ -25,7 +25,7 @@ import {createCustomEvent} from '../../../src/event-helper';
 import {dict} from '../../../src/utils/object';
 import {dispatchCustomEvent} from '../../../src/dom';
 import {isExperimentOn} from '../../../src/experiments';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /** @const {string} */
 const TAG = 'amp-stream-gallery';
diff --git a/extensions/amp-timeago/0.1/amp-timeago.js b/extensions/amp-timeago/0.1/amp-timeago.js
index a034d97f3563..ebe7e1c1f0dc 100644
--- a/extensions/amp-timeago/0.1/amp-timeago.js
+++ b/extensions/amp-timeago/0.1/amp-timeago.js
@@ -20,7 +20,7 @@ import {
   observeWithSharedInOb,
   unobserveWithSharedInOb,
 } from '../../../src/viewport-observer';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 export class AmpTimeAgo extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-timeago/1.0/amp-timeago.js b/extensions/amp-timeago/1.0/amp-timeago.js
index c2d91d086ea7..b45bc3d93481 100644
--- a/extensions/amp-timeago/1.0/amp-timeago.js
+++ b/extensions/amp-timeago/1.0/amp-timeago.js
@@ -16,7 +16,7 @@
 
 import {BaseElement} from './base-element';
 import {isExperimentOn} from '../../../src/experiments';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /** @const {string} */
 const TAG = 'amp-timeago';
diff --git a/extensions/amp-truncate-text/0.1/binary-search.js b/extensions/amp-truncate-text/0.1/binary-search.js
index c1d3b3dd4afd..08a3f4356610 100644
--- a/extensions/amp-truncate-text/0.1/binary-search.js
+++ b/extensions/amp-truncate-text/0.1/binary-search.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {pureDevAssert as devAssert} from '../../../src/assert';
+import {pureDevAssert as devAssert} from '../../../src/core/assert';
 
 /**
  * When no matching index is found, whether to stop on the next or previous
diff --git a/extensions/amp-video/1.0/amp-video.js b/extensions/amp-video/1.0/amp-video.js
index 8dc0b7d98eb1..0c533363145c 100644
--- a/extensions/amp-video/1.0/amp-video.js
+++ b/extensions/amp-video/1.0/amp-video.js
@@ -17,7 +17,7 @@
 import {CSS} from '../../../build/amp-video-1.0.css';
 import {VideoBaseElement} from './base-element';
 import {isExperimentOn} from '../../../src/experiments';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /** @const {string} */
 const TAG = 'amp-video';
diff --git a/extensions/amp-viewer-integration/0.1/findtext.js b/extensions/amp-viewer-integration/0.1/findtext.js
index 6cb3542f2826..4a20710e36a1 100644
--- a/extensions/amp-viewer-integration/0.1/findtext.js
+++ b/extensions/amp-viewer-integration/0.1/findtext.js
@@ -15,7 +15,7 @@
  */
 
 import {computedStyle} from '../../../src/style';
-import {pureDevAssert as devAssert} from '../../../src/assert';
+import {pureDevAssert as devAssert} from '../../../src/core/assert';
 
 /**
  * Simple implementation of CircularBuffer.
diff --git a/extensions/amp-vimeo/0.1/amp-vimeo.js b/extensions/amp-vimeo/0.1/amp-vimeo.js
index 251bf08b7617..f55ac4f208de 100644
--- a/extensions/amp-vimeo/0.1/amp-vimeo.js
+++ b/extensions/amp-vimeo/0.1/amp-vimeo.js
@@ -32,7 +32,7 @@ import {getMode} from '../../../src/mode';
 import {installVideoManagerForDoc} from '../../../src/service/video-manager-impl';
 import {isLayoutSizeDefined} from '../../../src/layout';
 import {once} from '../../../src/utils/function';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 const TAG = 'amp-vimeo';
 
diff --git a/extensions/amp-vine/0.1/amp-vine.js b/extensions/amp-vine/0.1/amp-vine.js
index e31a14ea1b94..fc4e057e585b 100644
--- a/extensions/amp-vine/0.1/amp-vine.js
+++ b/extensions/amp-vine/0.1/amp-vine.js
@@ -16,7 +16,7 @@
 
 import {Services} from '../../../src/services';
 import {isLayoutSizeDefined} from '../../../src/layout';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 class AmpVine extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-yotpo/0.1/amp-yotpo.js b/extensions/amp-yotpo/0.1/amp-yotpo.js
index 8b8ec4287376..9a5e34ed0237 100644
--- a/extensions/amp-yotpo/0.1/amp-yotpo.js
+++ b/extensions/amp-yotpo/0.1/amp-yotpo.js
@@ -19,7 +19,7 @@ import {getIframe} from '../../../src/3p-frame';
 import {isLayoutSizeDefined} from '../../../src/layout';
 import {listenFor} from '../../../src/iframe-helper';
 import {removeElement} from '../../../src/dom';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 export class AmpYotpo extends AMP.BaseElement {
   /** @param {!AmpElement} element */
diff --git a/extensions/amp-youtube/1.0/amp-youtube.js b/extensions/amp-youtube/1.0/amp-youtube.js
index 7ff9b7ccd544..bf85f262ed29 100644
--- a/extensions/amp-youtube/1.0/amp-youtube.js
+++ b/extensions/amp-youtube/1.0/amp-youtube.js
@@ -17,7 +17,7 @@
 import {BaseElement} from './base-element';
 import {CSS} from '../../../build/amp-youtube-1.0.css';
 import {isExperimentOn} from '../../../src/experiments';
-import {pureUserAssert as userAssert} from '../../../src/assert';
+import {pureUserAssert as userAssert} from '../../../src/core/assert';
 
 /** @const {string} */
 const TAG = 'amp-youtube';
diff --git a/src/action-constants.js b/src/action-constants.js
index 58b2aad23c7b..ef76030a5bd1 100644
--- a/src/action-constants.js
+++ b/src/action-constants.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {pureDevAssert as devAssert} from './assert';
+import {pureDevAssert as devAssert} from './core/assert';
 
 /**
  * Key string in an action arguments map for an unparsed object literal string.
diff --git a/src/context/component-hooks.js b/src/context/component-hooks.js
index c4fd533b8626..ead46dadf17d 100644
--- a/src/context/component-hooks.js
+++ b/src/context/component-hooks.js
@@ -15,7 +15,7 @@
  */
 
 import {areEqualOrdered} from '../utils/array';
-import {pureDevAssert as devAssert} from '../assert';
+import {pureDevAssert as devAssert} from '../core/assert';
 import {tryCallback} from './scheduler';
 
 const EMPTY_DEPS = [];
diff --git a/src/context/node.js b/src/context/node.js
index db8ea3e230eb..c613aac4bfb6 100644
--- a/src/context/node.js
+++ b/src/context/node.js
@@ -15,7 +15,7 @@
  */
 
 import {Values} from './values';
-import {pureDevAssert as devAssert} from '../assert';
+import {pureDevAssert as devAssert} from '../core/assert';
 import {getMode} from '../mode';
 import {pushIfNotExist, removeItem} from '../utils/array';
 import {throttleTail} from './scheduler';
diff --git a/src/context/prop.js b/src/context/prop.js
index 7a0a65ec1011..c1ea7916adc0 100644
--- a/src/context/prop.js
+++ b/src/context/prop.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {pureDevAssert as devAssert} from '../assert';
+import {pureDevAssert as devAssert} from '../core/assert';
 
 const EMPTY_DEPS = [];
 
diff --git a/src/cookies.js b/src/cookies.js
index 97a7de791621..fc00d017fd24 100644
--- a/src/cookies.js
+++ b/src/cookies.js
@@ -22,7 +22,7 @@ import {
   tryDecodeUriComponent,
 } from './url';
 import {urls} from './config';
-import {pureUserAssert as userAssert} from './assert';
+import {pureUserAssert as userAssert} from './core/assert';
 
 const TEST_COOKIE_NAME = '-test-amp-cookie-tmp';
 
diff --git a/src/css.js b/src/css.js
index 2be4ebb30af9..cda23a49e663 100644
--- a/src/css.js
+++ b/src/css.js
@@ -15,7 +15,7 @@
  */
 
 import {cssEscape} from '../third_party/css-escape/css-escape';
-import {pureDevAssert as devAssert} from './assert';
+import {pureDevAssert as devAssert} from './core/assert';
 
 /**
  * Asserts that name is just an alphanumeric word, and does not contain
diff --git a/src/element-service.js b/src/element-service.js
index e998eaa3d4d7..137954d2fb65 100644
--- a/src/element-service.js
+++ b/src/element-service.js
@@ -24,7 +24,7 @@ import {
   getServicePromiseOrNull,
   getServicePromiseOrNullForDoc,
 } from './service';
-import {pureUserAssert as userAssert} from './assert';
+import {pureUserAssert as userAssert} from './core/assert';
 
 /**
  * Returns a promise for a service for the given id and window. Also expects an
diff --git a/src/extension-analytics.js b/src/extension-analytics.js
index b2fb74841b57..2b6ce602aacc 100644
--- a/src/extension-analytics.js
+++ b/src/extension-analytics.js
@@ -17,7 +17,7 @@
 import {CommonSignals} from './common-signals';
 import {Services} from './services';
 import {createElementWithAttributes, removeElement} from './dom';
-import {pureDevAssert as devAssert} from './assert';
+import {pureDevAssert as devAssert} from './core/assert';
 import {dict} from './utils/object';
 import {isArray, toWin} from './types';
 import {triggerAnalyticsEvent} from './analytics';
diff --git a/src/finite-state-machine.js b/src/finite-state-machine.js
index f54a4041be3e..3a301e3178a8 100644
--- a/src/finite-state-machine.js
+++ b/src/finite-state-machine.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {pureDevAssert as devAssert} from './assert';
+import {pureDevAssert as devAssert} from './core/assert';
 
 /**
  * @template STATE
diff --git a/src/gesture.js b/src/gesture.js
index de067e04b6a0..d47aceadca5d 100644
--- a/src/gesture.js
+++ b/src/gesture.js
@@ -16,7 +16,7 @@
 
 import {Observable} from './observable';
 import {Pass} from './pass';
-import {pureDevAssert as devAssert} from './assert';
+import {pureDevAssert as devAssert} from './core/assert';
 import {findIndex} from './utils/array';
 import {supportsPassiveEventListener} from './event-helper-listen';
 import {toWin} from './types';
diff --git a/src/modal.js b/src/modal.js
index af65ef1278a2..a825a79b25e0 100644
--- a/src/modal.js
+++ b/src/modal.js
@@ -1,4 +1,4 @@
-import {pureDevAssert as devAssert} from './assert';
+import {pureDevAssert as devAssert} from './core/assert';
 import {isConnectedNode, rootNodeFor} from './dom';
 import {toArray} from './types';
 
diff --git a/src/preact/base-element.js b/src/preact/base-element.js
index 391c607a4bbc..0e38c5e1aa53 100644
--- a/src/preact/base-element.js
+++ b/src/preact/base-element.js
@@ -40,7 +40,7 @@ import {
   parseBooleanAttribute,
 } from '../dom';
 import {dashToCamelCase} from '../string';
-import {pureDevAssert as devAssert} from '../assert';
+import {pureDevAssert as devAssert} from '../core/assert';
 import {dict, hasOwn, map} from '../utils/object';
 import {getDate} from '../utils/date';
 import {getMode} from '../mode';
diff --git a/src/render-delaying-services.js b/src/render-delaying-services.js
index cf7ebf6325b6..81d59b143362 100644
--- a/src/render-delaying-services.js
+++ b/src/render-delaying-services.js
@@ -15,7 +15,7 @@
  */
 
 import {Services} from './services';
-import {pureDevAssert as devAssert} from './assert';
+import {pureDevAssert as devAssert} from './core/assert';
 import {getServicePromise} from './service';
 
 /**
diff --git a/src/service/core-services.js b/src/service/core-services.js
index 7dff1350a3e9..06a360dd1a5a 100644
--- a/src/service/core-services.js
+++ b/src/service/core-services.js
@@ -15,7 +15,7 @@
  */
 
 import {adoptServiceForEmbedDoc} from '../service';
-import {pureDevAssert as devAssert} from '../assert';
+import {pureDevAssert as devAssert} from '../core/assert';
 import {installActionServiceForDoc} from './action-impl';
 import {installBatchedXhrService} from './batched-xhr-impl';
 import {installCidService} from './cid-impl';
diff --git a/src/service/custom-element-registry.js b/src/service/custom-element-registry.js
index 8a3142f7d113..5e69f75a7fd4 100644
--- a/src/service/custom-element-registry.js
+++ b/src/service/custom-element-registry.js
@@ -19,7 +19,7 @@ import {Services} from '../services';
 import {createCustomElementClass, stubbedElements} from '../custom-element';
 import {extensionScriptsInNode} from '../element-service';
 import {reportError} from '../error';
-import {pureUserAssert as userAssert} from '../assert';
+import {pureUserAssert as userAssert} from '../core/assert';
 
 /**
  * @param {!Window} win
diff --git a/src/service/hidden-observer-impl.js b/src/service/hidden-observer-impl.js
index b4e7c16d89a8..d59dffa2554b 100644
--- a/src/service/hidden-observer-impl.js
+++ b/src/service/hidden-observer-impl.js
@@ -15,7 +15,7 @@
  */
 
 import {Observable} from '../observable';
-import {pureDevAssert as devAssert} from '../assert';
+import {pureDevAssert as devAssert} from '../core/assert';
 import {registerServiceBuilderForDoc} from '../service';
 
 /**
diff --git a/src/service/owners-impl.js b/src/service/owners-impl.js
index da654b18791f..d1daa1674702 100644
--- a/src/service/owners-impl.js
+++ b/src/service/owners-impl.js
@@ -17,7 +17,7 @@
 import {OwnersInterface} from './owners-interface';
 import {Resource} from './resource';
 import {Services} from '../services';
-import {pureDevAssert as devAssert} from '../assert';
+import {pureDevAssert as devAssert} from '../core/assert';
 import {isArray} from '../types';
 import {registerServiceBuilderForDoc} from '../service';
 
diff --git a/src/service/position-observer/position-observer-worker.js b/src/service/position-observer/position-observer-worker.js
index 89dca611678e..a4cd57a8dc86 100644
--- a/src/service/position-observer/position-observer-worker.js
+++ b/src/service/position-observer/position-observer-worker.js
@@ -15,7 +15,7 @@
  */
 
 import {Services} from '../../services';
-import {pureDevAssert as devAssert} from '../../assert';
+import {pureDevAssert as devAssert} from '../../core/assert';
 import {
   layoutRectEquals,
   layoutRectLtwh,
diff --git a/src/service/task-queue.js b/src/service/task-queue.js
index b70a5488c8b0..113823f9a1be 100644
--- a/src/service/task-queue.js
+++ b/src/service/task-queue.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {pureDevAssert as devAssert} from '../assert';
+import {pureDevAssert as devAssert} from '../core/assert';
 
 /**
  * The internal structure for the task.
diff --git a/src/service/template-impl.js b/src/service/template-impl.js
index e31e938e403e..fd8300f7009b 100644
--- a/src/service/template-impl.js
+++ b/src/service/template-impl.js
@@ -17,7 +17,7 @@
 import {Deferred} from '../utils/promise';
 import {getService, registerServiceBuilder} from '../service';
 import {rootNodeFor, scopedQuerySelector} from '../dom';
-import {pureUserAssert as userAssert} from '../assert';
+import {pureUserAssert as userAssert} from '../core/assert';
 
 /**
  * @fileoverview
diff --git a/src/service/variable-source.js b/src/service/variable-source.js
index d8a41df78bb9..7700b474e807 100644
--- a/src/service/variable-source.js
+++ b/src/service/variable-source.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 import {Services} from '../services';
-import {pureDevAssert as devAssert} from '../assert';
+import {pureDevAssert as devAssert} from '../core/assert';
 import {isAmp4Email} from '../format';
 import {isFiniteNumber} from '../types';
 import {loadPromise} from '../event-helper';
diff --git a/src/ssr-template-helper.js b/src/ssr-template-helper.js
index 41bf47c99946..184536717cc5 100644
--- a/src/ssr-template-helper.js
+++ b/src/ssr-template-helper.js
@@ -17,7 +17,7 @@
 import {dict} from './utils/object';
 import {isArray} from './types';
 import {toStructuredCloneable} from './utils/xhr-utils';
-import {pureUserAssert as userAssert} from './assert';
+import {pureUserAssert as userAssert} from './core/assert';
 
 /**
  * @typedef {{
diff --git a/src/static-template.js b/src/static-template.js
index e6b8422274a7..de24dc9834b3 100644
--- a/src/static-template.js
+++ b/src/static-template.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {pureDevAssert as devAssert} from './assert';
+import {pureDevAssert as devAssert} from './core/assert';
 import {map} from './utils/object.js';
 
 let htmlContainer;
diff --git a/src/url.js b/src/url.js
index 27182c446ed0..fea5e7cc3b7d 100644
--- a/src/url.js
+++ b/src/url.js
@@ -22,7 +22,7 @@ import {isArray} from './types';
 import {parseQueryString_} from './url-parse-query-string';
 import {tryDecodeUriComponent_} from './url-try-decode-uri-component';
 import {urls} from './config';
-import {pureUserAssert as userAssert} from './assert';
+import {pureUserAssert as userAssert} from './core/assert';
 
 /**
  * @type {!JsonObject}
diff --git a/src/utils/bytes.js b/src/utils/bytes.js
index a137d5872d80..7bda98d0d3f7 100644
--- a/src/utils/bytes.js
+++ b/src/utils/bytes.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {pureDevAssert as devAssert} from '../assert';
+import {pureDevAssert as devAssert} from '../core/assert';
 
 /**
  * Interpret a byte array as a UTF-8 string.
diff --git a/src/utils/detached-dom-stream.js b/src/utils/detached-dom-stream.js
index 1e25e985eb9a..9c439fa287a8 100644
--- a/src/utils/detached-dom-stream.js
+++ b/src/utils/detached-dom-stream.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {pureDevAssert as devAssert} from '../assert';
+import {pureDevAssert as devAssert} from '../core/assert';
 
 export class DetachedDomStream {
   /**
diff --git a/src/utils/math.js b/src/utils/math.js
index 3623e881519c..048d9d30202f 100644
--- a/src/utils/math.js
+++ b/src/utils/math.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {pureDevAssert as devAssert} from '../assert';
+import {pureDevAssert as devAssert} from '../core/assert';
 
 /**
  * Maps a value in a first range to its equivalent in a second range
diff --git a/src/viewport-observer.js b/src/viewport-observer.js
index f81385673e5d..35c8636e1f41 100644
--- a/src/viewport-observer.js
+++ b/src/viewport-observer.js
@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-import {pureDevAssert as devAssert} from '../src/assert';
+import {pureDevAssert as devAssert} from '../src/core/assert';
 import {getMode} from './mode';
 import {isIframed} from './dom';
 import {toWin} from './types';

From be9e94b739212f23903f02c21f070a8935b603f2 Mon Sep 17 00:00:00 2001
From: Ryan Cebulko <ryan@cebulko.com>
Date: Mon, 1 Mar 2021 14:44:40 -0500
Subject: [PATCH 12/15] remove double imports

---
 extensions/amp-accordion/1.0/base-element.js | 2 +-
 extensions/amp-selector/1.0/base-element.js  | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/extensions/amp-accordion/1.0/base-element.js b/extensions/amp-accordion/1.0/base-element.js
index 1652bdf974bc..278386181065 100644
--- a/extensions/amp-accordion/1.0/base-element.js
+++ b/extensions/amp-accordion/1.0/base-element.js
@@ -23,7 +23,7 @@ import {
 } from './component';
 import {PreactBaseElement} from '../../../src/preact/base-element';
 import {childElementsByTag, toggleAttribute} from '../../../src/dom';
-import {pureDevAssert as devAssert} from '../../../src/core/core/assert';
+import {pureDevAssert as devAssert} from '../../../src/core/assert';
 import {dict, memo} from '../../../src/utils/object';
 import {forwardRef} from '../../../src/preact/compat';
 import {toArray} from '../../../src/types';
diff --git a/extensions/amp-selector/1.0/base-element.js b/extensions/amp-selector/1.0/base-element.js
index 27caa3a1999f..01dfba651546 100644
--- a/extensions/amp-selector/1.0/base-element.js
+++ b/extensions/amp-selector/1.0/base-element.js
@@ -23,7 +23,7 @@ import {
   toggleAttribute,
   tryFocus,
 } from '../../../src/dom';
-import {pureDevAssert as devAssert} from '../../../src/core/core/assert';
+import {pureDevAssert as devAssert} from '../../../src/core/assert';
 import {dict} from '../../../src/utils/object';
 import {toArray} from '../../../src/types';
 import {useCallback, useLayoutEffect, useRef} from '../../../src/preact';

From 3dd0755c313724fb1fd33a936f4b1e46064bb238 Mon Sep 17 00:00:00 2001
From: Ryan Cebulko <ryan@cebulko.com>
Date: Mon, 1 Mar 2021 16:05:48 -0500
Subject: [PATCH 13/15] fix dep-check config

---
 build-system/test-configs/dep-check-config.js | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/build-system/test-configs/dep-check-config.js b/build-system/test-configs/dep-check-config.js
index 23cfbe1a44e8..9f7d735bd1b4 100644
--- a/build-system/test-configs/dep-check-config.js
+++ b/build-system/test-configs/dep-check-config.js
@@ -100,7 +100,7 @@ exports.rules = [
       '3p/**->src/utils/function.js',
       '3p/**->src/utils/object.js',
       '3p/**->src/utils/promise.js',
-      '3p/**->src/assert.js',
+      '3p/**->src/core/assert.js',
       '3p/**->src/log.js',
       '3p/**->src/types.js',
       '3p/**->src/string.js',
@@ -136,7 +136,7 @@ exports.rules = [
       'ads/**->src/utils/dom-fingerprint.js',
       'ads/**->src/utils/object.js',
       'ads/**->src/utils/rate-limit.js',
-      'ads/**->src/assert.js',
+      'ads/**->src/core/assert.js',
       'ads/**->src/log.js',
       'ads/**->src/mode.js',
       'ads/**->src/url.js',

From cdb52b1f5345a8b05afba0a57eebe13da3f7d934 Mon Sep 17 00:00:00 2001
From: Ryan Cebulko <ryan@cebulko.com>
Date: Mon, 1 Mar 2021 17:10:13 -0500
Subject: [PATCH 14/15] stringify elements

---
 src/core/assert.js       | 13 +++++++++++++
 test/unit/test-assert.js |  2 ++
 2 files changed, 15 insertions(+)

diff --git a/src/core/assert.js b/src/core/assert.js
index c7c6b4997ae9..3ef75a15b15e 100644
--- a/src/core/assert.js
+++ b/src/core/assert.js
@@ -21,6 +21,19 @@ import {
 
 /** @fileoverview Dependency-free assertion helpers for use in Preact. */
 
+/**
+ * Converts an element to a readable string; all other types are unchanged.
+ * @param {*} val
+ * @return {*}
+ */
+function elementStringOrPassThru(val) {
+  // Do check equivalent to `val instanceof Element` without cross-window bug
+  if (val?.nodeType == 1) {
+    return val.tagName.toLowerCase() + (val.id ? `#${val.id}` : '');
+  }
+  return val;
+}
+
 /**
  * User error class for use in Preact. Use of sentinel string instead of a
  * boolean to check user errors because errors could be rethrown by some native
diff --git a/test/unit/test-assert.js b/test/unit/test-assert.js
index bd1321fe035a..08dc1f72a9c4 100644
--- a/test/unit/test-assert.js
+++ b/test/unit/test-assert.js
@@ -64,6 +64,7 @@ describes.sandboxed('assertions', {}, () => {
 
   it('should add element and message info', () => {
     const div = document.createElement('div');
+    div.id = 'testId';
     let error;
     try {
       devAssert(false, '%s a %s b %s', div, 2, 3);
@@ -71,6 +72,7 @@ describes.sandboxed('assertions', {}, () => {
       error = e;
     }
 
+    expect(error.toString()).to.match(/div#testId a 2 b 3/);
     expect(error.associatedElement).to.equal(div);
     expect(error.messageArray).to.deep.equal([div, 2, 3]);
   });

From cbc6756f6ecd8332827e1325cb334642a86dafd0 Mon Sep 17 00:00:00 2001
From: Ryan Cebulko <ryan@cebulko.com>
Date: Tue, 2 Mar 2021 16:53:16 -0500
Subject: [PATCH 15/15] Fix merge bug

---
 src/core/assert.js | 13 -------------
 1 file changed, 13 deletions(-)

diff --git a/src/core/assert.js b/src/core/assert.js
index 3ef75a15b15e..c7c6b4997ae9 100644
--- a/src/core/assert.js
+++ b/src/core/assert.js
@@ -21,19 +21,6 @@ import {
 
 /** @fileoverview Dependency-free assertion helpers for use in Preact. */
 
-/**
- * Converts an element to a readable string; all other types are unchanged.
- * @param {*} val
- * @return {*}
- */
-function elementStringOrPassThru(val) {
-  // Do check equivalent to `val instanceof Element` without cross-window bug
-  if (val?.nodeType == 1) {
-    return val.tagName.toLowerCase() + (val.id ? `#${val.id}` : '');
-  }
-  return val;
-}
-
 /**
  * User error class for use in Preact. Use of sentinel string instead of a
  * boolean to check user errors because errors could be rethrown by some native