@build-break Back out "[RN] Remove Map/Set from RN Open Source"

Summary: Backing out D14786123 as it's causing failures on fbandroid/stable.

Differential Revision:
D15693250
Ninja: sheriff

fbshipit-source-id: 526054d4f0dab2a811f2328540e7418ece9810b1

Libraries/Core/InitializeCore.js

@@ -28,6 +28,7 @@
 const start = Date.now();
 
 require('./setUpGlobals');
+require('./polyfillES6Collections');
 require('./setUpSystrace');
 require('./setUpErrorHandling');
 require('./polyfillPromise');

Libraries/Core/__tests__/MapAndSetPolyfills-test.js

@@ -0,0 +1,102 @@
+/**
+ * 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.
+ *
+ * @format
+ * @emails oncall+react_native
+ */
+'use strict';
+
+// Save these methods so that we can restore them afterward.
+const {freeze, seal, preventExtensions} = Object;
+
+function setup() {
+  jest.setMock('../../vendor/core/_shouldPolyfillES6Collection', () => true);
+}
+
+function cleanup() {
+  Object.assign(Object, {freeze, seal, preventExtensions});
+}
+
+describe('Map polyfill', () => {
+  setup();
+
+  const Map = require('../../vendor/core/Map');
+
+  it('is not native', () => {
+    const getCode = Function.prototype.toString.call(Map.prototype.get);
+    expect(getCode).not.toContain('[native code]');
+    expect(getCode).toContain('getIndex');
+  });
+
+  it('should tolerate non-extensible object keys', () => {
+    const map = new Map();
+    const key = Object.create(null);
+    Object.freeze(key);
+    map.set(key, key);
+    expect(map.size).toBe(1);
+    expect(map.has(key)).toBe(true);
+    map.delete(key);
+    expect(map.size).toBe(0);
+    expect(map.has(key)).toBe(false);
+  });
+
+  it('should not get confused by prototypal inheritance', () => {
+    const map = new Map();
+    const proto = Object.create(null);
+    const base = Object.create(proto);
+    map.set(proto, proto);
+    expect(map.size).toBe(1);
+    expect(map.has(proto)).toBe(true);
+    expect(map.has(base)).toBe(false);
+    map.set(base, base);
+    expect(map.size).toBe(2);
+    expect(map.get(proto)).toBe(proto);
+    expect(map.get(base)).toBe(base);
+  });
+
+  afterAll(cleanup);
+});
+
+describe('Set polyfill', () => {
+  setup();
+
+  const Set = require('../../vendor/core/Set');
+
+  it('is not native', () => {
+    const addCode = Function.prototype.toString.call(Set.prototype.add);
+    expect(addCode).not.toContain('[native code]');
+  });
+
+  it('should tolerate non-extensible object elements', () => {
+    const set = new Set();
+    const elem = Object.create(null);
+    Object.freeze(elem);
+    set.add(elem);
+    expect(set.size).toBe(1);
+    expect(set.has(elem)).toBe(true);
+    set.add(elem);
+    expect(set.size).toBe(1);
+    set.delete(elem);
+    expect(set.size).toBe(0);
+    expect(set.has(elem)).toBe(false);
+  });
+
+  it('should not get confused by prototypal inheritance', () => {
+    const set = new Set();
+    const proto = Object.create(null);
+    const base = Object.create(proto);
+    set.add(proto);
+    expect(set.size).toBe(1);
+    expect(set.has(proto)).toBe(true);
+    expect(set.has(base)).toBe(false);
+    set.add(base);
+    expect(set.size).toBe(2);
+    expect(set.has(proto)).toBe(true);
+    expect(set.has(base)).toBe(true);
+  });
+
+  afterAll(cleanup);
+});

Libraries/Core/polyfillES6Collections.js

@@ -0,0 +1,27 @@
+/**
+ * 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 {polyfillGlobal} = require('../Utilities/PolyfillFunctions');
+
+/**
+ * Polyfill ES6 collections (Map and Set).
+ * If you don't need these polyfills, don't use InitializeCore; just directly
+ * require the modules you need from InitializeCore for setup.
+ */
+const _shouldPolyfillCollection = require('../vendor/core/_shouldPolyfillES6Collection');
+if (_shouldPolyfillCollection('Map')) {
+  // $FlowFixMe: even in strict-local mode Flow expects Map to be Flow-typed
+  polyfillGlobal('Map', () => require('../vendor/core/Map'));
+}
+if (_shouldPolyfillCollection('Set')) {
+  // $FlowFixMe: even in strict-local mode Flow expects Set to be Flow-typed
+  polyfillGlobal('Set', () => require('../vendor/core/Set'));
+}