Alex Hunt
1387f521fd
Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/46696 Following D62161923, we began to lose sync with modern Flow syntax when Metro's `transformer.hermesParser` option is disabled. This config option loads Babel for transformation (instead of `hermes-parser`), which requires a Babel plugin to parse (not strip) Flow syntax. This diff migrates us away from `babel/plugin-syntax-flow` (see also https://github.com/babel/babel/issues/16264) and uses the modern [`babel-plugin-syntax-hermes-parser`](https://www.npmjs.com/package/babel-plugin-syntax-hermes-parser) instead (a component of the modern Hermes Parser stack). Following this change, new projects that unset `transformer.hermesParser` will compile. Resolves https://github.com/facebook/react-native/issues/46601. Changelog: [General][Fixed] - Fix parsing of modern Flow syntax when `transformer.hermesParser = false` is configured in Metro config Reviewed By: cipolleschi Differential Revision: D63535216 fbshipit-source-id: d2c6ddec030d89e2698e03b76194cf3568d04e6b
@react-native/babel-preset
Babel presets for React Native applications. React Native itself uses this Babel preset by default when transforming your app's source code.
If you wish to use a custom Babel configuration by writing a babel.config.js file in your project's root directory, you must specify all the plugins necessary to transform your code. React Native does not apply its default Babel configuration in this case. So, to make your life easier, you can use this preset to get the default configuration and then specify more plugins that run before it.
Usage
As mentioned above, you only need to use this preset if you are writing a custom babel.config.js file.
Installation
Install @react-native/babel-preset in your app:
with npm:
npm i @react-native/babel-preset --save-dev
or with yarn:
yarn add -D @react-native/babel-preset
Configuring Babel
Then, create a file called babel.config.js in your project's root directory. The existence of this babel.config.js file will tell React Native to use your custom Babel configuration instead of its own. Then load this preset:
{
"presets": ["module:@react-native/babel-preset"]
}
You can further customize your Babel configuration by specifying plugins and other options. See Babel's babel.config.js documentation to learn more.
Help and Support
If you get stuck configuring Babel, please ask a question on Stack Overflow or find a consultant for help. If you discover a bug, please open up an issue.