Make explicit extensions in imports work.

[NullVoxPopuli]

Resolves #628

See repro repo: https://stackblitz.com/edit/stackblitz-starters-g58nhp?file=examples%2Fts-addon-node16%2Fpackage.json,examples%2Fts-addon-node16%2Fsrc%2Findex.ts

• pnpm build
• poke around in the declarations directories

Using the patch from here: #628 (comment)
(where TS would allow)

And the test from here: https://github.com/typed-ember/glint/pull/648/files#diff-a835cb215198fc0a50973a4ae3bf66eac5a4b0bc21293fa29fc70888d663f797

The downside to this approach is "what if" someone has a foo.gts.ts file (probably co-located with a foo.gts.hbs file) -- but like, realistically, this isn't a thing they can use unless they're going half-in on static component references.

Notes:

• subpath-imports: https://nodejs.org/api/packages.html#subpath-imports
  this feature can't be used because all subpath-imports must start with a # to differentiate from packages.
• subpath-exports: https://nodejs.org/api/packages.html#subpath-exports
  not relevant because from a library perspective, our own exports are not referenced except by consumers

Testing locally

The Glint Terminal

• clone this branch
• yarn
• yarn build
• delete glint-monorepo-test-utils from @glint/cores package.json's devDependencies

Repro Terminal

• download extract and cd into the repro
• pnpm i
• pnpm link ~/path/to/this/branch/of/glint
• pnpm build

---

note that after every pnpm link, in order to work in the glint repo again, you'll need to re-run yarn, and un-delete the glint-monorepo-test-utils package.

[lifeart]

Wondering, is allowArbitraryExtensions may help us here? https://www.typescriptlang.org/tsconfig#allowArbitraryExtensions
Also, looks like we may have customConditions https://www.typescriptlang.org/tsconfig#customConditions dynamically generated

Interesting part: {file basename}.d.{extension}.ts - is proposed type definition for custom extensions, so, instead of having component.gts.d.ts we may need to use component.d.gts.ts

https://github.com/microsoft/TypeScript/issues/50133

[NullVoxPopuli]

@lifeart yeah, that sounds like a reasonable feature -- but we'd still need glint to to remove the extension during emitting.

So far, I've found it easiest, to work around the problem :(
Not ideal, but I don't know what the correct fix is yet. Maybe it's what you link to!