react-native/Libraries/Utilities/defineLazyObjectProperty.js
Rubén Norte d5e9e55fa3 Remove @providesModule from all modules
Summary:
This PR removes the need for having the `providesModule` tags in all the modules in the repository.

It configures Flow, Jest and Metro to get the module names from the filenames (`Libraries/Animated/src/nodes/AnimatedInterpolation.js` => `AnimatedInterpolation`)

* Checked the Flow configuration by running flow on the project root (no errors):

```
yarn flow
```

* Checked the Jest configuration by running the tests with a clean cache:

```
yarn jest --clearCache && yarn test
```

* Checked the Metro configuration by starting the server with a clean cache and requesting some bundles:

```
yarn run start --reset-cache
curl 'localhost:8081/IntegrationTests/AccessibilityManagerTest.bundle?platform=android'
curl 'localhost:8081/Libraries/Alert/Alert.bundle?platform=ios'
```

[INTERNAL] [FEATURE] [All] - Removed providesModule from all modules and configured tools.
Closes https://github.com/facebook/react-native/pull/18995

Reviewed By: mjesun

Differential Revision: D7729509

Pulled By: rubennorte

fbshipit-source-id: 892f760a05ce1fddb088ff0cd2e97e521fb8e825
2018-04-25 07:37:10 -07:00

65 lines
1.7 KiB
JavaScript

/**
* Copyright (c) 2013-present, Facebook, Inc.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*
* @flow
*/
'use strict';
/**
* Defines a lazily evaluated property on the supplied `object`.
*/
function defineLazyObjectProperty<T>(
object: Object,
name: string,
descriptor: {
get: () => T,
enumerable?: boolean,
writable?: boolean,
},
): void {
const {get} = descriptor;
const enumerable = descriptor.enumerable !== false;
const writable = descriptor.writable !== false;
let value;
let valueSet = false;
function getValue(): T {
// WORKAROUND: A weird infinite loop occurs where calling `getValue` calls
// `setValue` which calls `Object.defineProperty` which somehow triggers
// `getValue` again. Adding `valueSet` breaks this loop.
if (!valueSet) {
// Calling `get()` here can trigger an infinite loop if it fails to
// remove the getter on the property, which can happen when executing
// JS in a V8 context. `valueSet = true` will break this loop, and
// sets the value of the property to undefined, until the code in `get()`
// finishes, at which point the property is set to the correct value.
valueSet = true;
setValue(get());
}
return value;
}
function setValue(newValue: T): void {
value = newValue;
valueSet = true;
Object.defineProperty(object, name, {
value: newValue,
configurable: true,
enumerable,
writable,
});
}
Object.defineProperty(object, name, {
get: getValue,
set: setValue,
configurable: true,
enumerable,
});
}
module.exports = defineLazyObjectProperty;