85 lines
2.3 KiB
JavaScript
85 lines
2.3 KiB
JavaScript
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/**
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* Copyright (c) Facebook, Inc. and its affiliates.
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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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* @format
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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 (
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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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) {
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return object;
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}
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const keys = Object.keys(object);
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const hasOwnProperty = Object.prototype.hasOwnProperty;
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for (let i = 0; i < keys.length; i++) {
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const key = keys[i];
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if (hasOwnProperty.call(object, key)) {
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Object.defineProperty(object, key, {
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get: identity.bind(null, object[key]),
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});
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Object.defineProperty(object, key, {
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set: throwOnImmutableMutation.bind(null, key),
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});
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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 (let i = 0; i < keys.length; i++) {
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const key = keys[i];
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if (hasOwnProperty.call(object, 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 `' +
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key +
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'` with the value `' +
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JSON.stringify(value) +
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'` 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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