Cross-package extensionless gjs/gts imports don't function as expected

[davidtaylorhq]

We have a library package which contains gjs/gts files, and we're importing those in an application package in the same monorepo. For js/ts files, those kind of cross-package extensionless imports work correctly. For gjs/gts they don't work.

Once declarations are built for the library package, then the extensionless gjs/gts imports are resolved correctly.

Here's a repository with a minimal example: https://github.com/davidtaylorhq/glint-monorepo-test

In app-package/src/start-here.ts, we have:

import JsButton from "library-package/components/js-button";
import TsButton from "library-package/components/ts-button";

import GjsButton from "library-package/components/gjs-button";
import GtsButton from "library-package/components/gts-button";

The first two resolve correctly all the time. The second two raise a 'Cannot find module' error. After building the declarations for library-package, all four resolve correctly.

CLI reproduction would be:

git clone https://github.com/davidtaylorhq/glint-monorepo-test
cd glint-monorepo-test
pnpm i

pnpm ember-tsc -b # Fails with two "cannot find module" errors for the app, but builds declarations for the library

pnpm ember-tsc -b # Succeeds, because now there are declarations on disk

rm -rf library-package/declarations

pnpm ember-tsc -b # Fails again

Ideally we want to be able to work on this monorepo without needing to emit declarations.

[mansona]

If app depends on library-package then library-package needs to go first in your project definition here: https://github.com/davidtaylorhq/glint-monorepo-test/blob/main/tsconfig.json#L4

If you swap them around does it fix it? (remember to do a git clean -xdf to be sure that nothing is ambiently hanging around 😂 )

[davidtaylorhq]

Reordering the references does make ember-tsc -b succeed. But that's only because it's writing the declaration files to disk before it type-checks the app. The imports are still broken when viewing the files in VSCode (which doesn't write declaration files to disk).

I updated the repo to reorder the references, and also add noEmit: true. That allows us to reproduce the VSCode issue on the CLI with pnpm ember-tsc -b:

❯ pnpm ember-tsc -b
app-package/src/start-here.ts:7:23 - error TS2307: Cannot find module 'library-package/components/gjs-button' or its corresponding type declarations.

7 import GjsButton from "library-package/components/gjs-button";
                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

app-package/src/start-here.ts:10:23 - error TS2307: Cannot find module 'library-package/components/gts-button' or its corresponding type declarations.

10 import GtsButton from "library-package/components/gts-button";
                         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


Found 2 errors.