Add support for package subpaths for plugins

What is the problem you’re trying to solve?

Hello!

So I have a package called @rhds/tokens, which has a bunch of stuff in it, including:

• a main module that exports some js unrelated to stylelint at ./js/tokens.cjs
• a stylelint plugin module at ./plugins/stylelint.cjs

I don’t want to mark the stylelint plugin as the main module, because its not, but I’d like users to be able to load up the plugin in their config, which is possible by referencing the file in node_modules, but a little less aesthetic.

What solution would you like to see?

  plugins:
-   - ./node_modules/@rhds/tokens/plugins/stylelint.cjs
+   - '@rhds/tokens'

This could be accomplished nicely with a node module export conditions:

"exports": {
  "stylelint": {
    "require": "./plugins/stylelint.cjs",
    "import": "plugins/stylelint.js"
  }
}

[bennypowers]

i’ve used my own custom conditions in the past, and some tools like esbuild support them

[ybiquitous]

Currently, Stylelint imports a plugin module here:

https://github.com/stylelint/stylelint/blob/0967b9c3650812be83ae4c4dddb00e3958e4826d/lib/augmentConfig.js#L325

If we implement the feature, is it necessary to change the code above?

Also, do we need to add a CLI flag like --conditions=stylelint to the following shebang? (--conditions seems experimental, though)

https://github.com/stylelint/stylelint/blob/0967b9c3650812be83ae4c4dddb00e3958e4826d/bin/stylelint.js#L1

We would appreciate it if you have any code examples that would be helpful.