Add .cjs and .mjs files support

[ai]

Do you want to request a feature or report a bug?

bug

What is the current behavior?

If you have require('./index.cjs') you will have issue:

Error: While trying to resolve module `lib` from file `project/index.js`, the package `project/node_modules/lib/package.json` was successfully found. However, this package itself specifies a `main` module field that could not be resolved (`project/node_modules/lib/index.cjs`. Indeed, none of these files exist:

      * project/node_modules/lib/index.cjs(.native|.web.js|.native.js|.js|.web.json|.native.json|.json|.web.ts|.native.ts|.ts|.web.tsx|.native.tsx|.tsx)
      * project/node_modules/lib/index.cjs/index(.native|.web.js|.native.js|.js|.web.json|.native.json|.json|.web.ts|.native.ts|.ts|.web.tsx|.native.tsx|.tsx)

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.

1. Create empty project
2. Add lib.cjs
3. Create index.js with require('./lib.cjs')

What is the expected behavior?

Load .cjs files as any .js files.

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

• No Metro config
• Metro 0.59.0
• Node 13.11.0
• Yarn 1.22.4

Extra details

I opened this issue because users of my dual CJS/ESM project have a problem with using my lib to React Native
ai/nanoevents#44 (comment)

You had .mjs issue before, but it was closed because in 2017 it was not clear about .mjs standard. Now .mjs and .cjs is an official Node.js API.