components in v2 addon's app-js using index files broken

[simonihmig]

Given index-modules based file layout for colocated component files as supported by RFC481 in a v2 addon:

src
└── componennts
    └── fancy-button
        ├── index.ts
        └── index.hbs

And generating the package's app-js by the rollup plugin provided by @embroider/addon-dev:

{
  "ember-addon": {
    "version": 2,
    "type": "addon",
    "main": "addon-main.cjs",
    "app-js": {
      "./components/fancy-button/index.js": "./dist/_app_/components/fancy-button/index.js"
    }
  }
}

when building an app consuming the addon using Embroider v3.4.5 and "optimized" settings, it would fail with:

Module not found: Error: Can't resolve '#embroider_compat/components/fancy-button' in '[...]/test-app'

It does work work with either

• classic build w/ eai
• Emboider v2.x
• Embroider v3.4.5 w/ "safe" mode (no static components)

It will also work in Embroider v3.4.5 "optimized" when changing the app-js's left side to not use index modules:

-"./components/fancy-button/index.js": "./dist/_app_/components/fancy-button/index.js"
+"./components/fancy-button.js": "./dist/_app_/components/fancy-button/index.js"

So we could fix this by exposing the app-js not using index modules, but since index-modules are officially supported by RFC481, it looks like a bug in Embroider?

[NullVoxPopuli]

I think this can be customized via:
https://github.com/embroider-build/embroider/blob/main/packages/addon-dev/src/rollup-app-reexports.ts#L11

addon.appReexports(['**/*.js'], { mapFilename: (filename) => {
  if (filename.includes('/components/') && filename.endsWith('index.js')) {
    return path.dirname(filename) + '.js';
  }
} }),

does that work?

See also prior discussions:

• Index path is not implied #1220
• Windvis/fix/resolve nested layout components #1639
  • Add a v2 addon "nested layout" component test #1587
  • Resolve "nested layout" components #1596

tl;dr: we opted not to resolve this at the resolver layer, since it's an explicit app-js and package.json exports resolution configuration that causes the behavior you're seeing.

[mansona]

So this was recently fixed on main and it's likely just a bug in the component resolver. I could see some value fixing this on stable but I think we have diverged a bit much to be able to simply backport the change 🤔

[simonihmig]

@mansona are you able to point me to where this was fixed on main?

[simonihmig]

I think this can be customized via:

Yeah, I know this workaround exists. But the question in this issue was more where to properly fix this? Is this a bug in Embroider (seems so, as Chris confirmed), or should we bake that behaviour into the rollup plugin? I'd rather not want to introduce this workaround everywhere in user-land code, since index-modules is a supported thing.

[NullVoxPopuli]

since index-modules is a supported thing

Not in ESM node 😅 (which is a bit of an oversight for co-location -- I also learned this by running in to broken stuff (and as it turns out, this is what package.json#exports follows)).
I think the fix @mansona is talking about is the loose mode resolver rules, which had index behavior fixed here: #1794
Commented here: #1826 (review)
Actual fix here: https://github.com/embroider-build/embroider/pull/1794/files#diff-61967680c203e14cb9a3b2c252caca7d6b0ee9b285991dba6b728f6c54112a12R571