Running any postcss-cli command fails with

• "type": "module" in package.json, and
• TypeScript config file (postcss.config.ts)

Details

After support for .mjs was added in version 4 of this module, I expected ESM-mode TypeScript to work as well. Unfortunately, it does not.

The issue has to do with how TypeScript config files are loaded:

Using ts-node.register() / require() with "type": "module" is simply unsupported. See ts-node documentation.

Workaround

The ts-node documentation describes a valid workaround:

• You have moved your project to ESM but still have a config file, such as webpack.config.ts, which must be executed as CommonJS
  • …
  • Solution: Configure a module type override. Docs

Indeed, if I include

  "ts-node": {
    "moduleTypes": {
      "postcss.config.ts": "cjs"
    }
  }

in tsconfig.json then the error goes away.

Error (Logs|Stacks)

https://gist.github.com/TimothyGu/e65fcba3fd759cd6fa2e415ed2047b77#file-readme-md

Reproduction (Code)

See https://gist.github.com/TimothyGu/e65fcba3fd759cd6fa2e415ed2047b77

$ git clone https://gist.github.com/e65fcba3fd759cd6fa2e415ed2047b77.git testdir
$ cd testdir
$ yarn
$ node_modules/.bin/postcss test.css

Environment