react-native/Libraries/Utilities/deepFreezeAndThrowOnMutatio...

85 lines
2.3 KiB
JavaScript

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