Yarn workspaces

[igl]

The module resolver looking for your local eslint installation seems not to be compatible with yarn workspaces.

It apparently only looks into the ./node_modules folder in the rootDir and not the repo-root node_modules.

The Error:

 FAIL   eslint  packages/api/src/index.js
  ● Test suite failed to run

    Cannot find module '/Users/igl/wubba-lubba-dub-dub/packages/api/node_modules/eslint'

      at getLocalESLint (../../node_modules/jest-runner-eslint/build/utils/getLocalESLint.js:9:10)

[ljharb]

With yarn workspaces, wouldn't you still want each individual project to have the proper dev deps listed?

[igl]

You have no choice. Yarn will install everything in the repo root and create symlinks in your packages/app/node_modules/.bin/ folder pointing to it. Given that other packages have the same or a compatible semver in their devDeps.

[ljharb]

Right - so why wouldn’t the runner be able to find the symlink?

[igl]

Actually found the problem already very quickly looking at the code. Find-up is not the right way.
Right now it is basically doing "../“ until it finds a node_modules folder and then stops trying.

A proper require.resolve like lookup would be better. Maybe resolve-from instead of find-up would do the trick.

[ljharb]

The resolve module can do it by setting a basedir; that would be far better than using resolve-from.

[igl]

Using jest rootDir which commonly is the package root not the repo root... I think packages shouldnt explicitly know they live in a mono-repo.

Worse: if other packages have different semver of eslint and it WILL install in your package node_modules and setting the baseDir to repo-root will pick up the wrong version for you. Resolve-from picks up the closest installation starting from rootDir is the correct behaviour imo.

[ljharb]

I agree - I'm only saying that we won't be using the resolve-from module to do it :-)