Verifying type imports

[bdwain]

This one is similar to #1678 I think, but I'm interested in making this an error for no-extraneous-dependencies

import type { MyType } from 'my-missing-dep`

the situation where this comes up for me is in a monorepo with yarn workspaces, specifically for internal dependencies, but I guess I don't see why it needs to be limited to those. I have scenarios where I build some packages but not others, and that is determined by the package.json dependency tree. I tested in my project and I can get a missing package.json dependency to still build for a type import, which is where a lint rule would come in handy

Here's an example. If package A imports from package B, but forgets to mark it as a dependency in package.json, normally specifying that I want to build B won't build A either, so this wouldn't need a lint rule because it'd break. But if A happens to get built for another reason (it was already built and never deleted, or package C is also being built, which specifies a dep on A), it could mask the build/runtime error that I would get for missing the dependency. That's where the lint rule would come into play by making it clear at build time when I am missing the dependency.

This applies to types as well regular imports, so I think having an option to enable the check for those would be useful. I'm not 100% sure why it would make sense to ever disable TBH, so I kind of feel like it should be on by default, or not even an option, but that can be a separate question since I know it's a breaking change.

Thoughts?

[ljharb]

I agree that an option for this makes perfect sense.

[ljharb]

(obviously if we ever have a semver-major, we'd want to turn it on by default)

[bdwain]

great! I'll have a pr up soon

[bdwain]

#2543