commonjs-extension-resolution-loader: add experimental-specifier-resolution tests

commonjs-extension-resolution-loader/loader.js

@@ -1,27 +1,45 @@
-import { existsSync } from 'fs';
-import { createRequire } from 'module';
+import { builtinModules } from 'node:module';
 import { dirname } from 'path';
-import { URL, fileURLToPath, pathToFileURL } from 'url';
+import { cwd } from 'process';
+import { fileURLToPath, pathToFileURL } from 'url';
+import { promisify } from 'util';
 
-const require = createRequire(import.meta.url);
-const baseURL = pathToFileURL(process.cwd() + '/').href;
+import resolveCallback from 'resolve/async.js';
 
-export function resolve(specifier, context, defaultResolve) {
+const resolveAsync = promisify(resolveCallback);
+
+const baseURL = pathToFileURL(cwd() + '/').href;
+
+
+export async function resolve(specifier, context, next) {
   const { parentURL = baseURL } = context;
 
-  // `require.resolve` works with paths, not URLs, so convert to and from
+  if (specifier.startsWith('node:') || builtinModules.includes(specifier)) {
+    return next(specifier, context);
+  }
+
+  // `resolveAsync` works with paths, not URLs
   if (specifier.startsWith('file://')) {
     specifier = fileURLToPath(specifier);
   }
-  const basePath = dirname(fileURLToPath(parentURL));
-  const resolvedPath = require.resolve(specifier, {paths: [basePath]});
+  const parentPath = fileURLToPath(parentURL);
 
-  if (existsSync(resolvedPath)) {
-    return {
-      url: pathToFileURL(resolvedPath).href
-    };
+  let url;
+  try {
+    const resolution = await resolveAsync(specifier, {
+      basedir: dirname(parentPath),
+      // For whatever reason, --experimental-specifier-resolution=node doesn't search for .mjs extensions
+      // but it does search for index.mjs files within directories
+      extensions: ['.js', '.json', '.node', '.mjs'],
+    });
+    url = pathToFileURL(resolution).href;
+  } catch (error) {
+    if (error.code === 'MODULE_NOT_FOUND') {
+      // Match Node's error code
+      error.code = 'ERR_MODULE_NOT_FOUND';
+    }
+    throw error;
   }
 
-  // Let Node.js handle all other specifiers, such as package names
-  return defaultResolve(specifier, context, defaultResolve);
+  return next(url, context);
 }

commonjs-extension-resolution-loader/package.json

@@ -6,8 +6,11 @@
   "main": "./loader.js",
   "scripts": {
     "start": "npm test",
-    "test": "node test.js"
+    "test": "node test/basic.js && node test/test-esm-specifiers.js && node test/test-esm-specifiers-symlink.js"
   },
-  "author": "Geoffrey Booth <[email protected]>",
-  "license": "MIT"
+  "author": "Geoffrey Booth <[email protected]>",
+  "license": "MIT",
+  "dependencies": {
+    "resolve": "^1.22.1"
+  }
 }

commonjs-extension-resolution-loader/test/basic.js

@@ -0,0 +1,25 @@
+import { match } from 'assert';
+import { spawn } from 'child_process';
+import { execPath } from 'process';
+
+
+// Run this test yourself with debugging mode via:
+// node --inspect-brk --loader ./loader.js ./fixtures/index.js
+
+const child = spawn(execPath, [
+  '--loader',
+  './loader.js',
+  './test/basic-fixtures/index.js'
+]);
+
+let stdout = '';
+child.stdout.setEncoding('utf8');
+child.stdout.on('data', data => {
+  stdout += data;
+});
+
+child.on('close', (_code, _signal) => {
+  stdout = stdout.toString();
+  match(stdout, /hello from file\.js/);
+  match(stdout, /hello from folder\/index\.js/);
+});

commonjs-extension-resolution-loader/test/common.js

@@ -0,0 +1,34 @@
+// Ported from https://github.com/nodejs/node/blob/45f2258f74117e27ffced434a98ad6babc14f7fa/test/common/index.js
+
+import { spawn } from 'node:child_process';
+
+
+export function spawnPromisified(...args) {
+  let stderr = '';
+  let stdout = '';
+
+  const child = spawn(...args);
+  child.stderr.setEncoding('utf8');
+  child.stderr.on('data', (data) => { stderr += data; });
+  child.stdout.setEncoding('utf8');
+  child.stdout.on('data', (data) => { stdout += data; });
+
+  return new Promise((resolve, reject) => {
+    child.on('close', (code, signal) => {
+      resolve({
+        code,
+        signal,
+        stderr,
+        stdout,
+      });
+    });
+    child.on('error', (code, signal) => {
+      reject({
+        code,
+        signal,
+        stderr,
+        stdout,
+      });
+    });
+  });
+}

commonjs-extension-resolution-loader/test/fixtures/es-module-specifiers/index.mjs

@@ -0,0 +1,11 @@
+import explicit from 'explicit-main';
+import implicit from 'implicit-main';
+import implicitModule from 'implicit-main-type-module';
+import noMain from 'no-main-field';
+
+function getImplicitCommonjs () {
+  return import('implicit-main-type-commonjs');
+}
+
+export {explicit, implicit, implicitModule, getImplicitCommonjs, noMain};
+export default 'success';

commonjs-extension-resolution-loader/test/fixtures/es-module-specifiers/package-type-commonjs/a.js

@@ -0,0 +1 @@
+module.exports = 'a';

commonjs-extension-resolution-loader/test/fixtures/es-module-specifiers/package-type-commonjs/b.mjs

@@ -0,0 +1 @@
+export const b = 'b';

commonjs-extension-resolution-loader/test/fixtures/es-module-specifiers/package-type-commonjs/c.cjs

@@ -0,0 +1,5 @@
+module.exports = {
+  one: 1,
+  two: 2,
+  three: 3
+};

commonjs-extension-resolution-loader/test/fixtures/es-module-specifiers/package-type-commonjs/index.mjs

@@ -0,0 +1,21 @@
+// js file that is common.js
+import a from './a.js';
+// ESM with named export
+import {b} from './b.mjs';
+// import 'c.cjs';
+import cjs from './c.cjs';
+// proves cross boundary fun bits
+import jsAsEsm from '../package-type-module/a.js';
+
+// named export from core
+import {strictEqual, deepStrictEqual} from 'assert';
+
+strictEqual(a, jsAsEsm);
+strictEqual(b, 'b');
+deepStrictEqual(cjs, {
+  one: 1,
+  two: 2,
+  three: 3
+});
+
+export default 'commonjs';

commonjs-extension-resolution-loader/test/fixtures/es-module-specifiers/package-type-commonjs/package.json

@@ -0,0 +1,3 @@
+{
+  "type": "commonjs"
+}

commonjs-extension-resolution-loader/test/fixtures/es-module-specifiers/package-type-module/a.js

@@ -0,0 +1 @@
+export default 'a'

commonjs-extension-resolution-loader/test/fixtures/es-module-specifiers/package-type-module/b.mjs

@@ -0,0 +1 @@
+export const b = 'b';

commonjs-extension-resolution-loader/test/fixtures/es-module-specifiers/package-type-module/c.cjs

@@ -0,0 +1,5 @@
+module.exports = {
+  one: 1,
+  two: 2,
+  three: 3
+};

commonjs-extension-resolution-loader/test/fixtures/es-module-specifiers/package-type-module/index.js

@@ -0,0 +1,21 @@
+// ESM with only default
+import a from './a.js';
+// ESM with named export
+import {b} from './b.mjs';
+// import 'c.cjs';
+import cjs from './c.cjs';
+// import across boundaries
+import jsAsCjs from '../package-type-commonjs/a.js'
+
+// named export from core
+import {strictEqual, deepStrictEqual} from 'assert';
+
+strictEqual(a, jsAsCjs);
+strictEqual(b, 'b');
+deepStrictEqual(cjs, {
+  one: 1,
+  two: 2,
+  three: 3
+});
+
+export default 'module';

commonjs-extension-resolution-loader/test/fixtures/es-module-specifiers/package-type-module/package.json

@@ -0,0 +1,3 @@
+{
+  "type": "module"
+}

commonjs-extension-resolution-loader/test/fixtures/es-module-specifiers/package.json

@@ -0,0 +1 @@
+{}