mirror of
https://github.com/facebook/react-native.git
synced 2025-11-01 09:14:26 +00:00
Xuan Huang
d9a9ae38d1
Summary: Changelog: [Internal] If generators are provided natively, that should suggest that the JS source code did not go through the regenerator-transform (e.g. in Metro Hermes profile), then there is no need to set up the regenerator runtime. This should save some work during the Core initialization. Reviewed By: motiz88 Differential Revision: D29986751 fbshipit-source-id: 129f5122e8e4c05535ee2aa5da6970a66843e8cd
45 lines
1.4 KiB
JavaScript
45 lines
1.4 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.
|
|
*
|
|
* @flow strict-local
|
|
* @format
|
|
*/
|
|
|
|
'use strict';
|
|
|
|
const {polyfillGlobal} = require('../Utilities/PolyfillFunctions');
|
|
const {hasNativeConstructor} = require('../Utilities/FeatureDetection');
|
|
|
|
/**
|
|
* Set up regenerator.
|
|
* You can use this module directly, or just require InitializeCore.
|
|
*/
|
|
|
|
let hasNativeGenerator;
|
|
try {
|
|
// If this function was lowered by regenerator-transform, it will try to
|
|
// access `global.regeneratorRuntime` which doesn't exist yet and will throw.
|
|
hasNativeGenerator = hasNativeConstructor(function*() {},
|
|
'GeneratorFunction');
|
|
} catch {
|
|
// In this case, we know generators are not provided natively.
|
|
hasNativeGenerator = false;
|
|
}
|
|
|
|
// If generators are provided natively, which suggests that there was no
|
|
// regenerator-transform, then there is no need to set up the runtime.
|
|
if (!hasNativeGenerator) {
|
|
polyfillGlobal('regeneratorRuntime', () => {
|
|
// The require just sets up the global, so make sure when we first
|
|
// invoke it the global does not exist
|
|
delete global.regeneratorRuntime;
|
|
|
|
// regenerator-runtime/runtime exports the regeneratorRuntime object, so we
|
|
// can return it safely.
|
|
return require('regenerator-runtime/runtime'); // flowlint-line untyped-import:off
|
|
});
|
|
}
|