75 lines
2.2 KiB
JavaScript
75 lines
2.2 KiB
JavaScript
/**
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* Copyright (c) 2015-present, Facebook, Inc.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*
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* @providesModule deepFreezeAndThrowOnMutationInDev
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* @flow
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*/
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'use strict';
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/**
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* If your application is accepting different values for the same field over
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* time and is doing a diff on them, you can either (1) create a copy or
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* (2) ensure that those values are not mutated behind two passes.
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* This function helps you with (2) by freezing the object and throwing if
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* the user subsequently modifies the value.
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*
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* There are two caveats with this function:
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* - If the call site is not in strict mode, it will only throw when
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* mutating existing fields, adding a new one
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* will unfortunately fail silently :(
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* - If the object is already frozen or sealed, it will not continue the
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* deep traversal and will leave leaf nodes unfrozen.
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*
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* Freezing the object and adding the throw mechanism is expensive and will
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* only be used in DEV.
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*/
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function deepFreezeAndThrowOnMutationInDev<T: Object>(object: T): T {
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if (__DEV__) {
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if (typeof object !== 'object' ||
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object === null ||
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Object.isFrozen(object) ||
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Object.isSealed(object)) {
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return object;
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}
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var keys = Object.keys(object);
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for (var i = 0; i < keys.length; i++) {
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var key = keys[i];
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if (object.hasOwnProperty(key)) {
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object.__defineGetter__(key, identity.bind(null, object[key]));
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object.__defineSetter__(key, throwOnImmutableMutation.bind(null, key));
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}
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}
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Object.freeze(object);
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Object.seal(object);
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for (var i = 0; i < keys.length; i++) {
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var key = keys[i];
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if (object.hasOwnProperty(key)) {
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deepFreezeAndThrowOnMutationInDev(object[key]);
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}
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}
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}
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return object;
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}
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function throwOnImmutableMutation(key, value) {
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throw Error(
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'You attempted to set the key `' + key + '` with the value `' +
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JSON.stringify(value) + '` on an object that is meant to be immutable ' +
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'and has been frozen.'
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);
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}
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function identity(value) {
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return value;
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}
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module.exports = deepFreezeAndThrowOnMutationInDev;
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