Add readFragment_UNSTABLE to experimental package

Reviewed By: kassens

Differential Revision: D9772419

fbshipit-source-id: a51a16c87f8691c08b73dd541b4e5eb13d4dd88c

Author: Juan Tejada

packages/relay-experimental/helpers/readFragment_UNSTABLE.js

@@ -0,0 +1,67 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ */
+
+'use strict';
+
+const invariant = require('invariant');
+
+import type {
+  GraphQLTaggedNode,
+  IEnvironment,
+  Snapshot,
+  Variables,
+} from 'relay-runtime';
+
+function readFragment_UNSTABLE(
+  environment: IEnvironment,
+  fragment: GraphQLTaggedNode,
+  fragmentRef: mixed,
+  variables: Variables,
+): Snapshot | $ReadOnlyArray<Snapshot> {
+  invariant(
+    fragmentRef != null,
+    'readFragment_UNSTABLE: Expected fragmentRef to be provided',
+  );
+  const {
+    getFragment,
+    getSelector,
+    getSelectorList,
+  } = environment.unstable_internal;
+  const fragmentNode = getFragment(fragment);
+  if (fragmentNode.metadata && fragmentNode.metadata.plural === true) {
+    invariant(
+      Array.isArray(fragmentRef),
+      'Expected fragmentRef to be an array if fragment %s is marked as @relay(plural: true)',
+      fragmentNode.name,
+    );
+    const selectors = getSelectorList(variables, fragmentNode, fragmentRef);
+    invariant(
+      selectors != null,
+      'Expected to be able to read fragment %s',
+      fragmentNode.name,
+    );
+    return selectors.map(selector => environment.lookup(selector));
+  } else {
+    invariant(
+      !Array.isArray(fragmentRef),
+      'Expected fragmentRef not to be an array if fragment %s is not marked as @relay(plural: true)',
+      fragmentNode.name,
+    );
+    const selector = getSelector(variables, fragmentNode, fragmentRef);
+    invariant(
+      selector != null,
+      'Expected to be able to read fragment %s',
+      fragmentNode.name,
+    );
+    return environment.lookup(selector);
+  }
+}
+
+module.exports = readFragment_UNSTABLE;

packages/relay-experimental/helpers/readQuery_UNSTABLE.js

@@ -10,8 +10,6 @@
 
 'use strict';
 
-const invariant = require('invariant');
-
 import type {
   GraphQLTaggedNode,
   IEnvironment,
@@ -25,19 +23,11 @@ import type {
  */
 function readQuery_UNSTABLE(
   environment: IEnvironment,
-  gqlNode: GraphQLTaggedNode,
+  query: GraphQLTaggedNode,
   variables: Variables,
 ): Snapshot {
-  const {
-    getRequest,
-    isRequest,
-    createOperationSelector,
-  } = environment.unstable_internal;
-  invariant(
-    isRequest(gqlNode),
-    'readQuery_UNSTABLE: Expected graphql node to be a query',
-  );
-  const queryNode = getRequest(gqlNode);
+  const {getRequest, createOperationSelector} = environment.unstable_internal;
+  const queryNode = getRequest(query);
   const operation = createOperationSelector(queryNode, variables);
   return environment.lookup(operation.fragment);
 }