eslint-import-resolver-node's resolution does not match node's with respect to symlinks

[anomiex]

Consider this example project, structured similarly to what pnpm produces: t.tar.gz

The directory structure looks something like this:

t/
t/index.js
t/node_modules/
t/node_modules/b -> .pnpm/[email protected]/node_modules/b
t/node_modules/.pnpm/
t/node_modules/.pnpm/[email protected]/
t/node_modules/.pnpm/[email protected]/node_modules/
t/node_modules/.pnpm/[email protected]/node_modules/b/
t/node_modules/.pnpm/[email protected]/node_modules/b/index.js
t/node_modules/.pnpm/[email protected]/node_modules/b/package.json
t/node_modules/.pnpm/[email protected]/node_modules/c -> ../../[email protected]/node_modules/c
t/node_modules/.pnpm/[email protected]/
t/node_modules/.pnpm/[email protected]/node_modules/
t/node_modules/.pnpm/[email protected]/node_modules/c/
t/node_modules/.pnpm/[email protected]/node_modules/c/index.js
t/node_modules/.pnpm/[email protected]/node_modules/c/package.json
t/package.json

Of particular note, package b depends on c, and pnpm structures things as above so that t/index.js won't see c as a phantom dependency. c exports a named export 'foo', and b rexports that with export * from 'c'.

When t/index.js imports b, standard Node module resoluton resolves that via the symlink t/node_modules/b, returning the absolute realpath /some/absolute/path/t/node_modules/.pnpm/[email protected]/node_modules/b/index.js. Resolving c relative to that path finds it via the symlink t/node_modules/.pnpm/[email protected]/node_modules/c.

eslint-import-resolver-node's resolution differs in one key respect: by default, instead of returning the absolute realpath /some/absolute/path/t/node_modules/.pnpm/[email protected]/node_modules/b/index.js, it returns /some/absolute/path/t/node_modules/b/index.js instead. It then (correctly) cannot resolve c relative to that path.

A relevant eslint.config.js to use with the above could look like this:

import importPlugin from 'eslint-plugin-import';

export default [ importPlugin.flatConfigs.recommended ];

which will produce the following false positive due to this bug

  1:10  error  foo not found in 'b'  import/named

---

If you want a "real" reproduction, starting in an empty project:

1. Create a package.json with "type": "module" (or use extension .mjs instead of .js in steps 3 and 4).
2. Run pnpm add eslint eslint-plugin-import @playwright/test.
3. Create the above eslint.config.js.
4. Create a JS file containing import { expect } from '@playwright/test';.
5. Run eslint on that file.

---

As for a fix, it looks like setting preserveSymlinks: false in

eslint-plugin-import/resolvers/node/index.js

Lines 11 to 20 in d5f2950

	function opts(file, config, packageFilter) {
	return Object.assign({ // more closely matches Node (#333)
	// plus 'mjs' for native modules! (#939)
	extensions: ['.mjs', '.js', '.json', '.node'],
	}, config, {
	// path.resolve will handle paths relative to CWD
	basedir: path.dirname(path.resolve(file)),
	packageFilter,
	});
	}

should do it. As a workaround this can be set in the eslint config with

{
    settings: {
        'import/resolver': {
            node: {
                preserveSymlinks: false,
            },
        }
    }
}

I note the README for the resolve package you use recommends setting preserveSymlinks: false to match Node's behavior; as far as I can tell, preserving symlinks was only the default in Node for a short time between 6.0.0 and 6.2.0, although the documentation as to the expected behavior was unclear before that.

[ljharb]

jestjs/jest#5356 (comment) has some more of the context/history as well.

You are correct that this value should be set to false by default. The reason that we don't do that in the node resolver at the moment is because that would be a breaking change.