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Critical improvements for Map and Set polyfills.
Summary: Pull Request resolved: #21492 Differential Revision: D10288094 Pulled By: cpojer fbshipit-source-id: b1ca7344dda3043553be6945614b439a0f42a46a
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/** | ||
* 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'; | ||
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// Save these methods so that we can restore them afterward. | ||
const {freeze, seal, preventExtensions} = Object; | ||
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function setup() { | ||
jest.setMock('../../vendor/core/_shouldPolyfillES6Collection', () => true); | ||
jest.unmock('_wrapObjectFreezeAndFriends'); | ||
require('_wrapObjectFreezeAndFriends'); | ||
} | ||
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function cleanup() { | ||
Object.assign(Object, {freeze, seal, preventExtensions}); | ||
} | ||
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describe('Map polyfill', () => { | ||
setup(); | ||
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const Map = require('Map'); | ||
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it('is not native', () => { | ||
const getCode = Function.prototype.toString.call(Map.prototype.get); | ||
expect(getCode).not.toContain('[native code]'); | ||
expect(getCode).toContain('getIndex'); | ||
}); | ||
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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); | ||
}); | ||
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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); | ||
}); | ||
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afterAll(cleanup); | ||
}); | ||
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describe('Set polyfill', () => { | ||
setup(); | ||
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const Set = require('Set'); | ||
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it('is not native', () => { | ||
const addCode = Function.prototype.toString.call(Set.prototype.add); | ||
expect(addCode).not.toContain('[native code]'); | ||
}); | ||
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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); | ||
}); | ||
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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); | ||
}); | ||
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afterAll(cleanup); | ||
}); |
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Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,37 @@ | ||
/** | ||
* 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. | ||
* | ||
* @author Ben Newman (@benjamn) <ben@benjamn.com> | ||
* @flow | ||
* @format | ||
*/ | ||
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'use strict'; | ||
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let testMap; // Initialized lazily. | ||
function getTestMap() { | ||
return testMap || (testMap = new (require('./Map'))()); | ||
} | ||
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// Wrap Object.{freeze,seal,preventExtensions} so each function adds its | ||
// argument to a Map first, which gives our ./Map.js polyfill a chance to | ||
// tag the object before it becomes non-extensible. | ||
["freeze", "seal", "preventExtensions"].forEach(name => { | ||
const method = Object[name]; | ||
if (typeof method === "function") { | ||
(Object: any)[name] = function (obj) { | ||
try { | ||
// If .set succeeds, also call .delete to avoid leaking memory. | ||
getTestMap().set(obj, obj).delete(obj); | ||
} finally { | ||
// If .set fails, the exception will be silently swallowed | ||
// by this return-from-finally statement, and the method will | ||
// behave exactly as it did before it was wrapped. | ||
return method.call(Object, obj); | ||
} | ||
}; | ||
} | ||
}); |