Do you want to request a feature or report a bug?
Bug / improvement for metro-react-native-babel-preset

What is the current behavior?

Error: Unexpected token: name (_000) in file App.tsx at 16:25

A build error that makes little sense in the context of a larger code base. The line:col isn't true to the original code, I had to console.log from within /metro/src/JSTransformer/worker.js to find the problematic line.

If the current behavior is a bug, please provide the steps to reproduce and a minimal repository on GitHub that we can yarn install and yarn test.

• react-native init MyApp --template react-native-template-typescript
• Use ES Numeric Separators syntax in your code, e.g. const thousand = 1_000;
• Try to bundle the project for release

Minimal repository reproducing the issue:

• git clone https://github.com/westphalen/metro-babel-preset-numeric-separators
• yarn install
• yarn build

What is the expected behavior?
Since the boilerplate project is set up to support TypeScript and es2017/esnext, one would expect that ES Numeric Separators were supported out of the box.

Solution
yarn install @babel/plugin-proposal-numeric-separator

Update babel.config.js with this line:

  plugins: ['@babel/plugin-proposal-numeric-separator'],

Would suggest this plugin is included by default in metro-react-native-babel-preset

Please provide your exact Metro configuration and mention your Metro, node, yarn/npm version and operating system.

• macOS 10.15.7
• node -v v10.22.0
• "metro-react-native-babel-preset": "0.63.0"
• metro "0.58.0"