import/extensions: ignorePackages doesn't work in .mjs file

[dynst]

Adding this rule:

      "import/extensions": ["warn", "ignorePackages"],

In a .ts file, there's no warning for this, the package import is successfully ignored:

import prettier from "eslint-plugin-prettier/recommended";

But in eslint.config.mjs, the package import isn't ignored by the ignorePackages setting:

eslint.config.mjs
  4:22  warning  Missing file extension "ts" for "eslint-plugin-prettier/recommended"  import/extensions

Not sure why it's recommending .ts in a non-TypeScript file, either. (adding .js wouldn't work either here though - it would be an error, because there's no ./recommended.js export, just a ./recommended. #3189)

[ljharb]

Are you sure that your eslint config is targeting mjs files with the same rules as ts files?