Support "link" as a valid dependency version in package.json

[ThisIsMissEm]

Currently when you're working on a project wherein you deliberately need to force using npm link for a dependency, e.g., you want the project to be developed against a local build of a package, then currently you need to have something like this in your dependencies:

  "dependencies": {
    "@inrupt/solid-client": "*"
  }

Such that tooling doesn't complain about @inrupt/solid-client not being installed, however, using a * (star / asterisks) version for a package isn't really recommended (I've seen tweets from @isaacs or @seldo about this).

I'd like to propose being able to instead write:

  "dependencies": {
    "@inrupt/solid-client": "link"
  }

Which when you run npm install, it would automatically execute npm link <pkg> for those, and if that fails, then print an error letting you know how to use npm link from the local copy of the dependency.

This would also be more ergonomic in places where you've multiple packages that you need to resolve from links; if you're using npm ci then I think the expected behaviour would be that this would fail, where as the former with * would succeed.

My primary use case for this is from example apps and e2e test apps where I want to build an application that's run against my package's latest code, without using relative imports.

[ljharb]

I believe this already works with a relative file path - file:./path/to/package.

[ThisIsMissEm]

Whilst file: could work, I don't think that's quite the same, similar but not quite the same.

[ljharb]

It creates a symlink in npm 5+ (before that, it copied)

[ThisIsMissEm]

Oh, maybe that works better! Does it still use the package.json and ensure that you're only requiring from the exports map?

[ljharb]

Yes, that's something node handles, which doesn't care if it's a symlink or not.