ESLint import resolver for ESM modules via package.json exports map

.eslintrc.js

module.exports = {
	settings: {
		// optionally, if TypeScript project:
		// 'import/parsers': {
		// 	'@typescript-eslint/parser': ['.ts', '.tsx'],
		// },
		'import/resolver': {
			// optionally, if TypeScript project:
			// https://github.com/alexgorbatchev/eslint-import-resolver-typescript
			// typescript: {
			// 	alwaysTryTypes: false,
			// 	project: ['./PATH/TO/tsconfig.json'],
			// },
			[path.resolve('./eslint-plugin-import-resolver.js')]: { someConfig: 1 },
    },
  },
},

README.md

ESLint import resolver for ESM modules via package.json exports map.

Relies on NPM package resolve.exports https://github.com/lukeed/resolve.exports

See:

• import-js/eslint-plugin-import#1868
• import-js/eslint-plugin-import#1810
• browserify/resolve#224
• wooorm/import-meta-resolve#2
• eslint-community/eslint-plugin-n#4
• mysticatea/eslint-plugin-node#255
• mysticatea/eslint-plugin-node#244
• mysticatea/eslint-plugin-node#258
• https://github.com/webpack/enhanced-resolve

eslint-plugin-import-resolver.js

const path = require('path');
const { resolve: resolveExports } = require('resolve.exports');

// optionally handle NodeJS built-ins just in case not handled by another ESLint module resolver in the chain
const { builtinModules } = require('module');
const builtins = new Set(builtinModules);

/**
 * @param {string} source source
 * @param {string} file file
 * @param {Object} _config config
 */
const resolve = (source, file, _config) => {
	if (builtins.has(source)) {
		// return { found: false }; // this also works?
		return { found: true, path: null };
	}
	try {
		const moduleId = require.resolve(source, { paths: [path.dirname(file)] });
		return { found: true, path: moduleId };
	} catch (/** @type {any} */ err) {
		if (err.code === 'MODULE_NOT_FOUND' && err.path?.endsWith('/package.json')) {
			const { name, module, main, exports } = require(err.path);
			const resolved = resolveExports({ name, module, main, exports }, source);
			const moduleId = path.join(path.dirname(err.path), resolved);
			return { found: true, path: moduleId };
		}
		return { found: false };
	}
};

module.exports = {
	interfaceVersion: 2,
	resolve,
};

Thank you. I am actually using a slightly different technique in my project, which I probably figured out after I posted this Gist (note to self: update the Gist!)

I am not sure which technique is "best" (in terms of of how the resolver stack is expected to work). Here's my additions:

const { builtinModules } = require('module');
const builtins = new Set(builtinModules);
// ...
const resolve = (source, file, _config) => {
	if (builtins.has(source)) {
		return { found: true, path: null };
	}
// ...

... as opposed to your fix which returns false after a successful require.resolve():

const { builtinModules } = require('module');
// ...
const resolve = (source, file, _config) => {
// ...
	const moduleId = require.resolve(source, { paths: [path.dirname(file)] });
	if (builtinModules.includes(moduleId)) {
		return { found: false };
	}
// ...

What do you think? (I'll run some tests at my end)

Ok, so I ran some additional tests.

Both "my" and "your" builtinModules solutions work (I tested them one by one, and I added an import typo like fss instead of fs to check false negatives / positives), ... however note in my case I have the following ESLint config:

settings: {
	react: {
		version: '17',
	},
	'import/parsers': {
		'@typescript-eslint/parser': ['.ts', '.tsx'],
	},
	'import/resolver': {
		// https://github.com/alexgorbatchev/eslint-import-resolver-typescript
		typescript: {
			alwaysTryTypes: false,
			project: ['./PATH/TO/tsconfig.json'],
		},
		[path.resolve('./eslint-plugin-import-resolver.cjs')]: { someConfig: 1 },
	},
}

...the important part is the import/resolver > typescript object, which when commented-out triggers either of our builtinModules conditionals (for example, for import { readFileSync } from "fs"). However if I leave my typescript settings in, then the builtinModules conditionals are never reached, as NodeJS module imports such as fs seem to be captured appropriately somewhere else in the ESLint resolver chain, outside of my custom resolver.

Hello.
Thank you for your problem resolve!

I have opinion on catching error.

//...
	catch (/** @type {any} */ err) {
		if (err.code === 'MODULE_NOT_FOUND' && err.path?.endsWith('/package.json')) {
			const { name, module, main, exports } = require(err.path);
			const resolved = resolveExports({ name, module, main, exports }, source);
			const moduleId = path.join(path.dirname(err.path), resolved);
			return { found: true, path: moduleId };
		}
//...

In my case, use subpath on node.

When cannot resolve moduleId in try, err.path is always package.json.

When moduleId cannot be defined in the try syntax, the error.path in the catch syntax is always package.json.
I think, printing a path that cannot be resolved is much useful. also it is already defined in 'source'.
EX:) error Unable to resolve path to module '#utils/error' import/no-unresolved

Then, what kind of error situation should the following syntax be executed?

//...
			const { name, module, main, exports } = require(err.path);
			const resolved = resolveExports({ name, module, main, exports }, source);
			const moduleId = path.join(path.dirname(err.path), resolved);
//...

Thank you. :)

Thanks for that solution.

I had to change the following line:

const possibleBuildinModuleId = moduleId.startsWith('node:') ? moduleId.slice(5) : moduleId;
if (builtinModules.includes(possibleBuildinModuleId)) {
   return { found: false };
}

Nevertheless, I get the following error:

 build-scripts\create-run-env\index.js:25:8
  ✖  25:8  Relative imports from parent directories are not allowed. Please either pass what you're importing through at runtime (dependency injection), move index.js to same directory as #build-scripts/constants.js or consider making #build-scripts/constants.js a package.  import/no-relative-parent-imports

  1 error

So, this solution does not cooperate with rule import/no-relative-parent-imports