From 40d62b96b4f51c6b1c38b5d32319e84b9b454ad7 Mon Sep 17 00:00:00 2001
From: offirgolan <offirgolan@gmail.com>
Date: Sun, 18 Nov 2018 22:24:10 -0800
Subject: [PATCH 1/4] feat(core): Support custom functions in matchRequestsBy
 config options

---
 docs/configuration.md                         | 180 ++++++++++++++----
 .../core/src/utils/normalize-request.js       |  32 +++-
 .../unit/utils/normalize-request-test.js      |  54 +++++-
 packages/@pollyjs/utils/package.json          |   2 +-
 yarn.lock                                     |   7 +-
 5 files changed, 212 insertions(+), 63 deletions(-)

diff --git a/docs/configuration.md b/docs/configuration.md
index e6425bda..ea092611 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -30,7 +30,7 @@ _Default_: `false`
 
 Logs requests and their responses to the console grouped by the recording name.
 
-__Example__
+**Example**
 
 ```js
 polly.configure({
@@ -46,7 +46,7 @@ _Default_: `true`
 If a request's recording is not found, pass-through to the server and
 record the response.
 
-__Example__
+**Example**
 
 ```js
 polly.configure({
@@ -62,7 +62,7 @@ _Default_: `false`
 If a request's recording has expired, pass-through to the server and
 record a new response.
 
-__Example__
+**Example**
 
 ```js
 polly.configure({
@@ -79,7 +79,7 @@ If `false`, Polly will throw when attempting to persist any failed requests.
 A request is considered to be a failed request when its response's status code
 is `< 200` or `≥ 300`.
 
-__Example__
+**Example**
 
 ```js
 polly.configure({
@@ -95,7 +95,7 @@ _Default_: `null`
 After how long the recorded request will be considered expired from the time
 it was persisted.
 
-__Example__
+**Example**
 
 ```js
 polly.configure({
@@ -118,7 +118,7 @@ The Polly mode. Can be one of the following:
 - `record`: Force Polly to record all requests. This will overwrite recordings that already exist.
 - `passthrough`: Passes all requests through directly to the server without recording or replaying.
 
-__Example__
+**Example**
 
 ```js
 polly.configure({
@@ -133,7 +133,7 @@ _Default_: `[]`
 
 The adapter(s) polly will hook into.
 
-__Example__
+**Example**
 
 ```js
 import XHRAdapter from '@pollyjs/adapter-xhr';
@@ -154,10 +154,10 @@ _Default_: `{}`
 
 Options to be passed into the adapters keyed by the adapter name.
 
-?> __NOTE:__ Check out the appropriate documentation pages for each adapter
+?> **NOTE:** Check out the appropriate documentation pages for each adapter
 for more details.
 
-__Example__
+**Example**
 
 ```js
 polly.configure({
@@ -176,7 +176,7 @@ _Default_: `null`
 
 The persister to use for recording and replaying requests.
 
-__Example__
+**Example**
 
 ```js
 import RESTPersister from '@pollyjs/persister-rest';
@@ -201,10 +201,10 @@ _Default_: `{}`
 
 Options to be passed into the persister keyed by the persister name.
 
-?> __NOTE:__ Check out the appropriate documentation pages for each persister
+?> **NOTE:** Check out the appropriate documentation pages for each persister
 for more details.
 
-__Example__
+**Example**
 
 ```js
 polly.configure({
@@ -227,7 +227,7 @@ recording will only contain the requests that were made during the lifespan
 of the Polly instance. When enabled, new requests will be appended to the
 recording file.
 
-__Example__
+**Example**
 
 ```js
 polly.configure({
@@ -244,7 +244,7 @@ _Default_: `Timing.fixed(0)`
 
 The timeout delay strategy used when replaying requests.
 
-__Example__
+**Example**
 
 ```js
 import { Timing } from '@pollyjs/core';
@@ -291,12 +291,12 @@ a GUID for the request.
 
 - ### method
 
-  _Type_: `Boolean`
+  _Type_: `Boolean | Function`
   _Default_: `true`
 
   The request method (e.g. `GET`, `POST`)
 
-  __Example__
+  **Example**
 
   ```js
   polly.configure({
@@ -304,16 +304,24 @@ a GUID for the request.
       method: false
     }
   });
+
+  polly.configure({
+    matchRequestsBy: {
+      method(method) {
+        return method.toLowerCase();
+      }
+    }
+  });
   ```
 
 - ### headers
 
-  _Type_: `Boolean | Object`
+  _Type_: `Boolean | Function | Object`
   _Default_: `true`
 
   The request headers.
 
-  __Example__
+  **Example**
 
   ```js
   polly.configure({
@@ -321,11 +329,20 @@ a GUID for the request.
       headers: false
     }
   });
+
+  polly.configure({
+    matchRequestsBy: {
+      headers(headers) {
+        delete headers['X-AUTH-TOKEN'];
+        return headers;
+      }
+    }
+  });
   ```
 
-  Specific headers can also be excluded:
+  Specific headers can also be excluded with the following:
 
-  __Example__
+  **Example**
 
   ```js
   polly.configure({
@@ -339,12 +356,12 @@ a GUID for the request.
 
 - ### body
 
-  _Type_: `Boolean`
+  _Type_: `Boolean | Function`
   _Default_: `true`
 
   The request body.
 
-  __Example__
+  **Example**
 
   ```js
   polly.configure({
@@ -352,6 +369,17 @@ a GUID for the request.
       body: false
     }
   });
+
+  polly.configure({
+    matchRequestsBy: {
+      body(body) {
+        const json = JSON.parse(body);
+
+        delete json.email;
+        return JSON.stringify(json);
+      }
+    }
+  });
   ```
 
 - ### order
@@ -372,7 +400,7 @@ a GUID for the request.
   await fetch('/models/1', { method: 'POST', body: JSON.stringify(model) });
 
   // Get our updated model
-  model = await fetch('/models/1').then(res => res.json())
+  model = await fetch('/models/1').then(res => res.json());
 
   // Assert that our change persisted
   expect(model.foo).to.equal('bar');
@@ -381,7 +409,7 @@ a GUID for the request.
   The order of the requests matter since the payload for the first and
   last fetch are different.
 
-  __Example__
+  **Example**
 
   ```js
   polly.configure({
@@ -393,12 +421,12 @@ a GUID for the request.
 
 - ### url.protocol
 
-  _Type_: `Boolean`
+  _Type_: `Boolean | Function`
   _Default_: `true`
 
   The request url protocol (e.g. `http:`).
 
-  __Example__
+  **Example**
 
   ```js
   polly.configure({
@@ -408,16 +436,26 @@ a GUID for the request.
       }
     }
   });
+
+  polly.configure({
+    matchRequestsBy: {
+      url: {
+        protocol(protocol) {
+          return 'https:';
+        }
+      }
+    }
+  });
   ```
 
 - ### url.username
 
-  _Type_: `Boolean`
+  _Type_: `Boolean | Function`
   _Default_: `true`
 
   Username of basic authentication.
 
-  __Example__
+  **Example**
 
   ```js
   polly.configure({
@@ -427,16 +465,25 @@ a GUID for the request.
       }
     }
   });
+  polly.configure({
+    matchRequestsBy: {
+      url: {
+        username(username) {
+          return 'username';
+        }
+      }
+    }
+  });
   ```
 
 - ### url.password
 
-  _Type_: `Boolean`
+  _Type_: `Boolean | Function`
   _Default_: `true`
 
   Password of basic authentication.
 
-  __Example__
+  **Example**
 
   ```js
   polly.configure({
@@ -445,17 +492,24 @@ a GUID for the request.
         password: false
       }
     }
+    matchRequestsBy: {
+      url: {
+        password(password) {
+          return 'password';
+        }
+      }
+    }
   });
   ```
 
 - ### url.hostname
 
-  _Type_: `Boolean`
+  _Type_: `Boolean | Function`
   _Default_: `true`
 
-  Host name with port number.
+  Host name without port number.
 
-  __Example__
+  **Example**
 
   ```js
   polly.configure({
@@ -465,16 +519,26 @@ a GUID for the request.
       }
     }
   });
+
+  polly.configure({
+    matchRequestsBy: {
+      url: {
+        hostname(hostname) {
+          return hostname.replace('.com', '.net');
+        }
+      }
+    }
+  });
   ```
 
 - ### url.port
 
-  _Type_: `Boolean`
+  _Type_: `Boolean | Function`
   _Default_: `true`
 
   Port number.
 
-  __Example__
+  **Example**
 
   ```js
   polly.configure({
@@ -484,22 +548,34 @@ a GUID for the request.
       }
     }
   });
+
+  polly.configure({
+    matchRequestsBy: {
+      url: {
+        port(port) {
+          return 3000;
+        }
+      }
+    }
+  });
   ```
 
 - ### url.pathname
 
-  _Type_: `Boolean`
+  _Type_: `Boolean | Function`
   _Default_: `true`
 
   URL path.
 
-  __Example__
+  **Example**
 
   ```js
   polly.configure({
     matchRequestsBy: {
       url: {
-        pathname: false
+        pathname(pathname) {
+          return pathname.replace('/api/v1', '/api');
+        }
       }
     }
   });
@@ -507,12 +583,12 @@ a GUID for the request.
 
 - ### url.query
 
-  _Type_: `Boolean`
+  _Type_: `Boolean | Function`
   _Default_: `true`
 
   Sorted query string.
 
-  __Example__
+  **Example**
 
   ```js
   polly.configure({
@@ -522,16 +598,26 @@ a GUID for the request.
       }
     }
   });
+
+  polly.configure({
+    matchRequestsBy: {
+      url: {
+        query(query) {
+          return { ...query, token: '' };
+        }
+      }
+    }
+  });
   ```
 
 - ### url.hash
 
-  _Type_: `Boolean`
+  _Type_: `Boolean | Function`
   _Default_: `false`
 
   The "fragment" portion of the URL including the pound-sign (`#`).
 
-  __Example__
+  **Example**
 
   ```js
   polly.configure({
@@ -541,4 +627,14 @@ a GUID for the request.
       }
     }
   });
+
+  polly.configure({
+    matchRequestsBy: {
+      url: {
+        hash(hash) {
+          return hash.replace(/token=[0-9]+/, '');
+        }
+      }
+    }
+  });
   ```
diff --git a/packages/@pollyjs/core/src/utils/normalize-request.js b/packages/@pollyjs/core/src/utils/normalize-request.js
index 0b71c88b..f62e7105 100644
--- a/packages/@pollyjs/core/src/utils/normalize-request.js
+++ b/packages/@pollyjs/core/src/utils/normalize-request.js
@@ -1,4 +1,5 @@
 import isObjectLike from 'lodash-es/isObjectLike';
+import isFunction from 'lodash-es/isFunction';
 import stringify from 'fast-json-stable-stringify';
 
 import parseUrl from './parse-url';
@@ -8,15 +9,23 @@ const { keys } = Object;
 const { isArray } = Array;
 const { parse } = JSON;
 
-export function method(method) {
-  return (method || 'GET').toUpperCase();
+export function method(method, config) {
+  return isFunction(config)
+    ? config(method || 'GET')
+    : (method || 'GET').toUpperCase();
 }
 
 export function url(url, config = {}) {
   const parsedUrl = parseUrl(url, true);
 
   // Remove any url properties that have been disabled via the config
-  keys(config).forEach(key => !config[key] && parsedUrl.set(key, ''));
+  keys(config).forEach(key => {
+    if (isFunction(config[key])) {
+      parsedUrl.set(key, config[key](parsedUrl[key]));
+    } else if (!config[key]) {
+      parsedUrl.set(key, '');
+    }
+  });
 
   // Sort Query Params
   if (isObjectLike(parsedUrl.query)) {
@@ -31,18 +40,23 @@ export function headers(headers, config) {
 
   if (isObjectLike(normalizedHeaders)) {
     normalizedHeaders = new HTTPHeaders(normalizedHeaders);
+  }
 
-    // Filter out excluded headers
-    if (isObjectLike(config) && isArray(config.exclude)) {
-      config.exclude.forEach(header => (normalizedHeaders[header] = null));
-    }
+  if (isFunction(config)) {
+    normalizedHeaders = config(normalizedHeaders);
+  } else if (
+    isObjectLike(normalizedHeaders) &&
+    isObjectLike(config) &&
+    isArray(config.exclude)
+  ) {
+    config.exclude.forEach(header => delete normalizedHeaders[header]);
   }
 
   return normalizedHeaders;
 }
 
-export function body(body) {
-  return body;
+export function body(body, config) {
+  return isFunction(config) ? config(body) : body;
 }
 
 export default {
diff --git a/packages/@pollyjs/core/tests/unit/utils/normalize-request-test.js b/packages/@pollyjs/core/tests/unit/utils/normalize-request-test.js
index 25751466..7b12e8dd 100644
--- a/packages/@pollyjs/core/tests/unit/utils/normalize-request-test.js
+++ b/packages/@pollyjs/core/tests/unit/utils/normalize-request-test.js
@@ -26,6 +26,10 @@ describe('Unit | Utils | Normalize Request', function() {
       expect(method('delete')).to.equal('DELETE');
       expect(method('option')).to.equal('OPTION');
     });
+
+    it('should support a custom fn', function() {
+      expect(method('GET', m => m.toLowerCase())).to.equal('get');
+    });
   });
 
   describe('headers', function() {
@@ -53,6 +57,23 @@ describe('Unit | Utils | Normalize Request', function() {
         )
       ).to.deep.equal({ accept: 'foo' });
     });
+
+    it('should support a custom fn', function() {
+      expect(
+        headers(
+          {
+            Accept: 'foo',
+            test: 'test',
+            'Content-Type': 'Bar'
+          },
+          headers => {
+            delete headers.test;
+
+            return headers;
+          }
+        )
+      ).to.deep.equal({ accept: 'foo', 'content-type': 'Bar' });
+    });
   });
 
   describe('url', function() {
@@ -62,7 +83,7 @@ describe('Unit | Utils | Normalize Request', function() {
       );
     });
 
-    it('should respect `hash` config', function() {
+    it('should respect `matchRequestsBy.url` config', function() {
       [
         [
           /* config options */
@@ -72,43 +93,54 @@ describe('Unit | Utils | Normalize Request', function() {
           /* expected when true */
           [true, 'http://hash-test.com?a=1&b=1&c=1#hello=world'],
           /* expected when false */
-          [false, 'http://hash-test.com?a=1&b=1&c=1']
+          [false, 'http://hash-test.com?a=1&b=1&c=1'],
+          /* expected when custom fn */
+          [
+            h => h.replace('=', '!='),
+            'http://hash-test.com?a=1&b=1&c=1#hello!=world'
+          ]
         ],
         [
           'protocol',
           'http://protocol-test.com',
           [true, 'http://protocol-test.com'],
-          [false, '//protocol-test.com']
+          [false, '//protocol-test.com'],
+          [p => p.replace('http', 'https'), 'https://protocol-test.com']
         ],
         [
           'query',
           'http://query-test.com?b=1&c=1&a=1',
           [true, 'http://query-test.com?a=1&b=1&c=1'],
-          [false, 'http://query-test.com']
+          [false, 'http://query-test.com'],
+          [q => ({ ...q, c: 2 }), 'http://query-test.com?a=1&b=1&c=2']
         ],
         [
           'username',
           'https://username:password@username-test.com',
           [true, 'https://username:password@username-test.com'],
-          [false, 'https://username-test.com']
+          [false, 'https://username-test.com'],
+          [u => `${u}123`, 'https://username123:password@username-test.com']
         ],
         [
           'password',
           'https://username:password@password-test.com',
           [true, 'https://username:password@password-test.com'],
-          [false, 'https://username@password-test.com']
+          [false, 'https://username@password-test.com'],
+          [p => `${p}123`, 'https://username:password123@password-test.com']
         ],
         [
           'port',
           'https://port-test.com:8000',
           [true, 'https://port-test.com:8000'],
-          [false, 'https://port-test.com']
+          [false, 'https://port-test.com'],
+          [p => Number(p) + 1, 'https://port-test.com:8001']
         ],
         [
           'pathname',
           'https://pathname-test.com/bar/baz',
           [true, 'https://pathname-test.com/bar/baz'],
-          [false, 'https://pathname-test.com']
+          [false, 'https://pathname-test.com'],
+          [p => p.replace('bar', 'foo'), 'https://pathname-test.com/foo/baz']
         ]
       ].forEach(([rule, input, ...options]) => {
         options.forEach(([optionValue, expectedOutput]) => {
@@ -121,4 +153,10 @@ describe('Unit | Utils | Normalize Request', function() {
       expect(url('/some/path')).to.equal('/some/path');
     });
   });
+
+  describe('body', function() {
+    it('should support a custom fn', function() {
+      expect(body('foo', b => b.toUpperCase())).to.equal('FOO');
+    });
+  });
 });
diff --git a/packages/@pollyjs/utils/package.json b/packages/@pollyjs/utils/package.json
index 15c52814..8d557e1c 100644
--- a/packages/@pollyjs/utils/package.json
+++ b/packages/@pollyjs/utils/package.json
@@ -39,7 +39,7 @@
   ],
   "license": "Apache-2.0",
   "dependencies": {
-    "url-parse": "^1.4.1"
+    "url-parse": "^1.4.4"
   },
   "devDependencies": {
     "npm-run-all": "^4.1.3",
diff --git a/yarn.lock b/yarn.lock
index fd0b5f09..c07d60c3 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -13408,9 +13408,10 @@ url-parse-lax@^3.0.0:
   dependencies:
     prepend-http "^2.0.0"
 
-url-parse@^1.4.1:
-  version "1.4.3"
-  resolved "https://registry.yarnpkg.com/url-parse/-/url-parse-1.4.3.tgz#bfaee455c889023219d757e045fa6a684ec36c15"
+url-parse@^1.4.4:
+  version "1.4.4"
+  resolved "https://registry.yarnpkg.com/url-parse/-/url-parse-1.4.4.tgz#cac1556e95faa0303691fec5cf9d5a1bc34648f8"
+  integrity sha512-/92DTTorg4JjktLNLe6GPS2/RvAd/RGr6LuktmWSMLEOa6rjnlrFXNgSbSmkNvCoL2T028A0a1JaJLzRMlFoHg==
   dependencies:
     querystringify "^2.0.0"
     requires-port "^1.0.0"

From cc79bb649ceccecab78a4218f3f1db609885721c Mon Sep 17 00:00:00 2001
From: offirgolan <offirgolan@gmail.com>
Date: Sun, 18 Nov 2018 22:44:05 -0800
Subject: [PATCH 2/4] refactor: Move serializeRequestBody into the identify
 method

---
 packages/@pollyjs/core/src/-private/request.js | 17 +++++++----------
 tests/integration/adapter-browser-tests.js     |  6 ++----
 2 files changed, 9 insertions(+), 14 deletions(-)

diff --git a/packages/@pollyjs/core/src/-private/request.js b/packages/@pollyjs/core/src/-private/request.js
index d9c962c4..41811c05 100644
--- a/packages/@pollyjs/core/src/-private/request.js
+++ b/packages/@pollyjs/core/src/-private/request.js
@@ -129,11 +129,8 @@ export default class PollyRequest extends HTTPBase {
     this.response = new PollyResponse();
     this.didRespond = false;
 
-    // Serialize the body which handles FormData + Blobs/Files
-    this.serializedBody = await this.serializeBody();
-
     // Setup this request's identifiers, id, and order
-    this._identify();
+    await this._identify();
 
     // Timestamp the request
     this.timestamp = timestamp();
@@ -172,10 +169,6 @@ export default class PollyRequest extends HTTPBase {
     await this._emit('response', this.response);
   }
 
-  async serializeBody() {
-    return serializeRequestBody(this.body);
-  }
-
   _overrideRecordingName(recordingName) {
     validateRecordingName(recordingName);
     this.recordingName = recordingName;
@@ -195,7 +188,7 @@ export default class PollyRequest extends HTTPBase {
     return this[ROUTE].emit(eventName, this, ...args);
   }
 
-  _identify() {
+  async _identify() {
     const polly = this[POLLY];
     const { _requests: requests } = polly;
     const { matchRequestsBy } = this.config;
@@ -205,12 +198,16 @@ export default class PollyRequest extends HTTPBase {
     keys(NormalizeRequest).forEach(key => {
       if (this[key] && matchRequestsBy[key]) {
         identifiers[key] = NormalizeRequest[key](
-          key === 'body' ? this.serializedBody : this[key],
+          this[key],
           matchRequestsBy[key]
         );
       }
     });
 
+    if (identifiers.body) {
+      identifiers.body = await serializeRequestBody(identifiers.body);
+    }
+
     // Store the identifiers for debugging and testing
     this.identifiers = freeze(identifiers);
 
diff --git a/tests/integration/adapter-browser-tests.js b/tests/integration/adapter-browser-tests.js
index 1507a3b4..246925b0 100644
--- a/tests/integration/adapter-browser-tests.js
+++ b/tests/integration/adapter-browser-tests.js
@@ -15,10 +15,10 @@ export default function adapterBrowserTests() {
     );
 
     server.post('/submit').intercept((req, res) => {
-      const body = req.serializedBody;
+      const body = req.identifiers.body;
 
       // Make sure the form data exists in the identifiers
-      expect(req.identifiers.body).to.include(recordingName);
+      expect(body).to.include(recordingName);
 
       expect(body).to.include(`string=${recordingName}`);
       expect(body).to.include(
@@ -49,8 +49,6 @@ export default function adapterBrowserTests() {
       // Make sure the form data exists in the identifiers
       expect(req.identifiers.body).to.equal(dataUrl);
 
-      expect(req.serializedBody).to.equal(dataUrl);
-
       res.sendStatus(200);
     });
 

From 23f2e7f2ac40f0a4287e542c2ec6355b3dca19c4 Mon Sep 17 00:00:00 2001
From: offirgolan <offirgolan@gmail.com>
Date: Mon, 19 Nov 2018 23:38:10 -0800
Subject: [PATCH 3/4] fix: Fix PR issues and add test case

---
 .../core/src/utils/normalize-request.js       | 23 ++++++++-----------
 .../unit/utils/normalize-request-test.js      | 18 +++++++++++----
 2 files changed, 23 insertions(+), 18 deletions(-)

diff --git a/packages/@pollyjs/core/src/utils/normalize-request.js b/packages/@pollyjs/core/src/utils/normalize-request.js
index f62e7105..879cb5f5 100644
--- a/packages/@pollyjs/core/src/utils/normalize-request.js
+++ b/packages/@pollyjs/core/src/utils/normalize-request.js
@@ -1,5 +1,4 @@
 import isObjectLike from 'lodash-es/isObjectLike';
-import isFunction from 'lodash-es/isFunction';
 import stringify from 'fast-json-stable-stringify';
 
 import parseUrl from './parse-url';
@@ -9,10 +8,12 @@ const { keys } = Object;
 const { isArray } = Array;
 const { parse } = JSON;
 
+function isFunction(fn) {
+  return typeof fn === 'function';
+}
+
 export function method(method, config) {
-  return isFunction(config)
-    ? config(method || 'GET')
-    : (method || 'GET').toUpperCase();
+  return isFunction(config) ? config(method) : method.toUpperCase();
 }
 
 export function url(url, config = {}) {
@@ -36,19 +37,13 @@ export function url(url, config = {}) {
 }
 
 export function headers(headers, config) {
-  let normalizedHeaders = headers;
+  const normalizedHeaders = new HTTPHeaders(headers);
 
-  if (isObjectLike(normalizedHeaders)) {
-    normalizedHeaders = new HTTPHeaders(normalizedHeaders);
+  if (isFunction(config)) {
+    return config(normalizedHeaders);
   }
 
-  if (isFunction(config)) {
-    normalizedHeaders = config(normalizedHeaders);
-  } else if (
-    isObjectLike(normalizedHeaders) &&
-    isObjectLike(config) &&
-    isArray(config.exclude)
-  ) {
+  if (isObjectLike(config) && isArray(config.exclude)) {
     config.exclude.forEach(header => delete normalizedHeaders[header]);
   }
 
diff --git a/packages/@pollyjs/core/tests/unit/utils/normalize-request-test.js b/packages/@pollyjs/core/tests/unit/utils/normalize-request-test.js
index 7b12e8dd..e4786176 100644
--- a/packages/@pollyjs/core/tests/unit/utils/normalize-request-test.js
+++ b/packages/@pollyjs/core/tests/unit/utils/normalize-request-test.js
@@ -14,10 +14,6 @@ describe('Unit | Utils | Normalize Request', function() {
   });
 
   describe('method', function() {
-    it('should default to GET', function() {
-      expect(method()).to.equal('GET');
-    });
-
     it('should handle all verbs', function() {
       expect(method('get')).to.equal('GET');
       expect(method('put')).to.equal('PUT');
@@ -74,6 +70,20 @@ describe('Unit | Utils | Normalize Request', function() {
         )
       ).to.deep.equal({ accept: 'foo', 'content-type': 'Bar' });
     });
+
+    it('should not mutate the original headers in the custom fn', function() {
+      const reqHeaders = { foo: 'bar' };
+
+      expect(
+        headers(reqHeaders, headers => {
+          delete headers.foo;
+
+          return headers;
+        })
+      ).to.deep.equal({});
+
+      expect(reqHeaders).to.deep.equal({ foo: 'bar' });
+    });
   });
 
   describe('url', function() {

From ef4916654949b446dac105f316d129523b62f6c8 Mon Sep 17 00:00:00 2001
From: offirgolan <offirgolan@gmail.com>
Date: Sat, 24 Nov 2018 12:57:43 -0800
Subject: [PATCH 4/4] docs: Add alert around modifying the request body

---
 docs/configuration.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/docs/configuration.md b/docs/configuration.md
index ea092611..66df37ec 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -361,6 +361,8 @@ a GUID for the request.
 
   The request body.
 
+  !> Please make sure you do not modify the passed in body. If you need to make changes, create a copy of it first. The body function receives the actual request body — any modifications to it will result with it being sent out with the request.
+
   **Example**
 
   ```js