📎 Implement `noUnresolvedImports` rule

[arendjr]

Description

Based on the following eslint-plugin-import rule: https://github.com/import-js/eslint-plugin-import/blob/HEAD/docs/rules/named.md

I think it makes sense to enable such a rule by default, but only let it run on JavaScript files. TypeScript files can be excluded, because they’ll be validated by the TypeScript compiler, and users would just see double diagnostics in their IDE (one from tsc, one from us). If necessary, we can always add an option later.

Inspiration can be taken from the noPrivateImports rule to see how to validate symbol lookups.

Relevant discussion: #5472

[ematipico]

I am a bit conflicted. tsc is known to be slow (CLI-wise). Wouldn't Biome fill the gap and catch this early in the users' CI pipelines?

[arendjr]

That's true, although it only applies in CI configurations where people actively run Biome in a pipeline before tsc, which seems quite an assumption. And realistically, given that people get IDE feedback on this issue already, and builds are generally broken completely if you push something with unresolved imports, I would expect it to be quite uncommon that we could successfully exit a CI run early based on that.

So my thought was on prioritising the user experience first. But yeah, if it turns out people indeed care about this use case, I'd be happy to make it an option.

[siketyan]

It's okay on CI because Biome exits first generally. But users will always get duplicated errors on IDE when using TypeScript.

[ematipico]

Then I don't understand the assumption. Isn't the TypeScript compiler able to catch this in JavaScript files? (assuming allowJs is enabled)

[arendjr]

Yes, but plenty of plain JavaScript users might not use the TypeScript compiler at all :)

[arendjr]

Note I created a separate discussion around disabling rules in domains: #5486

I didn’t want to hijack this issue, but it could provide an alternative approach to what I suggested here: If TypeScript users were to have this rule be disabled by default, the motivation for excluding .js files becomes irrelevant.