import-local may not work correctly in a Yarn workspace

[elliotdavies]

When using Yarn workspaces, such as in a monorepo setup, node_modules may be split across several locations like so:

- node_modules // workspace root
  - dep@v1
- app1
  - node_modules // nested projects
    - dep@v2
- lib1
  - node_modules

In this scenario an installed dependency may exist at the root node_modules or in one of the nested ones, depending on whether Yarn chooses to hoist it. The dependency may even exist in both places at different version numbers, as illustrated with dep above.

On this line, import-local effectively assumes that the directory it's running from is the sole local directory:

import-local/index.js

Line 10 in 101c451

const localFile = resolveCwd.silent(path.join(pkg.name, relativePath));

In a workspace however, import-local could be running from any of the node_modules folders. If for example import-local is installed at the workspace root and gets invoked by dep@v2, import-local will end up finding and invoking dep@v1, because that's in the same directory.

I would say this is a bug because neither version of dep was globally installed, and so I would expect import-local to return false-y.

[misterdjules]

Thanks for filing this @elliotdavies!

I just ran into the exact same issue when trying to run jest's executable at a given version from a nested directory in a monorepo. Instead, as you described above, it seems that import-local (which jest uses) runs the jest executable from the monorepo's root's node_modules directory, which in my use case can be at a different version.

[goodoldneon]

I'm running into this. What would the consequences be if we made this change to index.js?

'use strict';
const path = require('path');
const resolveCwd = require('resolve-cwd');
const pkgDir = require('pkg-dir');

module.exports = filename => {
	const globalDir = pkgDir.sync(path.dirname(filename));
	const relativePath = path.relative(globalDir, filename);
	const pkg = require(path.join(globalDir, 'package.json'));
	const localFile = resolveCwd.silent(path.join(pkg.name, relativePath));
	const filenameInLocalNodeModules = isFilenameInLocalNodeModules(filename, localFile);

	// Use `path.relative()` to detect local package installation,
	// because __filename's case is inconsistent on Windows
	// Can use `===` when targeting Node.js 8
	// See https://github.com/nodejs/node/issues/6624
	return !filenameInLocalNodeModules && localFile && path.relative(localFile, filename) !== '' && require(localFile);
};

function isFilenameInLocalNodeModules(filename, localFile) {
	if (localFile !== filename) {
		return true
	}

	const localNodeModules = path.join(process.cwd(), 'node_modules');

	return !path.relative(localNodeModules, filename).startsWith('..')
}

That changes fixes my issue, but I don't know if it creates other problems.