Expose --experimental-loader API inside plugins

[vjpr]

Issue description or question

Related: #696 (comment)

Plugins like https://github.com/Nodman/quokka-plugin-subdir are not possible in ESM environments without access to it.

Would be nice to allow hooking into this via the plugin API.

Alternative

Support subdir functionality in Quokka's hook.

Allow specifying the context.parentURL to use in the Loader.resolve hook from a plugin API.

module.exports = {
  before: async (config, setProjectDir) => { 
     const {pkgDir, pkg} = config
     // Also, allow user to locate the `pkgDir` from the package name (`pkg`) themselves.
    setProjectDir(pkgDir)
  }
}

({
  pkg: '@foo/bar',
})

// quokka scratch file

---

When I add my own experimental loader, Quokka adds theirs to the end:

  env: { params: { runner: '--experimental-loader=file:///my/esm-loader-wallaby.js --experimental-specifier-resolution=node --experimental-import-meta-resolve --experimental-vm-modules --experimental-top-level-await --experimental-loader "file:///Users/Vaughan/Library/Application%20Support/JetBrains/IntelliJIdeaVaughan/config/plugins/quokka-intellij/dist/runners/node/quokka@1.0.0/hooks.mjs"' } }

Otherwise, you could just add your loader and import Quokka's loader.

Chaining hooks is coming to Node.js soon - still in development which would solve this.

---

FYI, the hook api was recently changed too.

Note: In a previous version of this API, this was split across 3 separate, now deprecated, hooks (getFormat, getSource, and transformSource).
https://nodejs.org/api/esm.html#loadurl-context-defaultload