fix(esm): named import from CommonJS file (#33)

fixes #38

src/@types/module.d.ts

@@ -8,7 +8,7 @@ declare global {
 	}
 }
 
-declare module 'node:module' {
+declare module 'module' {
 	// https://nodejs.org/api/module.html#loadurl-context-nextload
 	interface LoadHookContext {
 		importAttributes: ImportAssertions;
@@ -17,6 +17,8 @@ declare module 'node:module' {
 	// CommonJS
 	export const _extensions: NodeJS.RequireExtensions;
 
+	export const _cache: NodeJS.Require['cache'];
+
 	export type Parent = {
 
 		/**
@@ -32,4 +34,9 @@ declare module 'node:module' {
 		isMain: boolean,
 		options?: Record<PropertyKey, unknown>,
 	): string;
+
+	interface LoadFnOutput {
+		// Added in https://github.com/nodejs/node/pull/43164
+		responseURL?: string;
+	}
 }

src/cjs/api/module-resolve-filename.ts

@@ -6,9 +6,34 @@ import type { NodeError } from '../../types.js';
 import { isRelativePath, fileUrlPrefix, tsExtensionsPattern } from '../../utils/path-utils.js';
 import { tsconfigPathsMatcher, allowJs } from '../../utils/tsconfig.js';
 
+type ResolveFilename = typeof Module._resolveFilename;
+
 const nodeModulesPath = `${path.sep}node_modules${path.sep}`;
 
-type ResolveFilename = typeof Module._resolveFilename;
+export const interopCjsExports = (
+	request: string,
+) => {
+	if (!request.startsWith('data:text/javascript,')) {
+		return request;
+	}
+
+	const queryIndex = request.indexOf('?');
+	if (queryIndex === -1) {
+		return request;
+	}
+
+	const searchParams = new URLSearchParams(request.slice(queryIndex + 1));
+	const realPath = searchParams.get('filePath');
+	if (realPath) {
+		// The CJS module cache needs to be updated with the actual path for export parsing to work
+		// https://github.com/nodejs/node/blob/v22.2.0/lib/internal/modules/esm/translators.js#L338
+		Module._cache[realPath] = Module._cache[request];
+		delete Module._cache[request];
+		request = realPath;
+	}
+
+	return request;
+};
 
 /**
  * Typescript gives .ts, .cts, or .mts priority over actual .js, .cjs, or .mjs extensions
@@ -60,6 +85,8 @@ export const createResolveFilename = (
 	isMain,
 	options,
 ) => {
+	request = interopCjsExports(request);
+
 	// Strip query string
 	const queryIndex = request.indexOf('?');
 	const query = queryIndex === -1 ? '' : request.slice(queryIndex);

src/esm/api/register.ts

@@ -1,6 +1,7 @@
 import module from 'node:module';
 import { MessageChannel, type MessagePort } from 'node:worker_threads';
 import type { Message } from '../types.js';
+import { interopCjsExports } from '../../cjs/api/module-resolve-filename.js';
 import { createScopedImport, type ScopedImport } from './scoped-import.js';
 
 export type TsconfigOptions = false | string;
@@ -31,13 +32,23 @@ export type Register = {
 	(options?: RegisterOptions): Unregister;
 };
 
+let cjsInteropApplied = false;
+
 export const register: Register = (
 	options,
 ) => {
 	if (!module.register) {
 		throw new Error(`This version of Node.js (${process.version}) does not support module.register(). Please upgrade to Node v18.9 or v20.6 and above.`);
 	}
 
+	if (!cjsInteropApplied) {
+		const { _resolveFilename } = module;
+		module._resolveFilename = (
+			request, _parent, _isMain, _options,
+		) => _resolveFilename(interopCjsExports(request), _parent, _isMain, _options);
+		cjsInteropApplied = true;
+	}
+
 	const { sourceMapsEnabled } = process;
 	process.setSourceMapsEnabled(true);
 

src/esm/hook/load.ts

@@ -1,14 +1,16 @@
 import { fileURLToPath } from 'node:url';
 import type { LoadHook } from 'node:module';
+import { readFile } from 'node:fs/promises';
 import type { TransformOptions } from 'esbuild';
 import { transform } from '../../utils/transform/index.js';
 import { transformDynamicImport } from '../../utils/transform/transform-dynamic-import.js';
 import { inlineSourceMap } from '../../source-map.js';
-import { isFeatureSupported, importAttributes } from '../../utils/node-features.js';
+import { isFeatureSupported, importAttributes, esmLoadReadFile } from '../../utils/node-features.js';
 import { parent } from '../../utils/ipc/client.js';
 import type { Message } from '../types.js';
 import { fileMatcher } from '../../utils/tsconfig.js';
 import { isJsonPattern, tsExtensionsPattern } from '../../utils/path-utils.js';
+import { parseEsm } from '../../utils/es-module-lexer.js';
 import { getNamespace } from './utils.js';
 import { data } from './initialize.js';
 
@@ -60,13 +62,31 @@ export const load: LoadHook = async (
 	}
 
 	const loaded = await nextLoad(url, context);
+	const filePath = url.startsWith('file://') ? fileURLToPath(url) : url;
+
+	if (
+		loaded.format === 'commonjs'
+		&& isFeatureSupported(esmLoadReadFile)
+		&& loaded.responseURL?.startsWith('file:') // Could be data:
+	) {
+		const code = await readFile(new URL(url), 'utf8');
+		const [, exports] = parseEsm(code);
+		if (exports.length > 0) {
+			const cjsExports = `module.exports={${
+				exports.map(exported => exported.n).filter(name => name !== 'default').join(',')
+			}}`;
+			const parameters = new URLSearchParams({ filePath });
+			loaded.responseURL = `data:text/javascript,${encodeURIComponent(cjsExports)}?${parameters.toString()}`;
+		}
+
+		return loaded;
+	}
 
 	// CommonJS and Internal modules (e.g. node:*)
 	if (!loaded.source) {
 		return loaded;
 	}
 
-	const filePath = url.startsWith('file://') ? fileURLToPath(url) : url;
 	const code = loaded.source.toString();
 
 	if (

src/utils/node-features.ts

@@ -53,3 +53,9 @@ export const importAttributes: Version[] = [
 export const testRunnerGlob: Version[] = [
 	[21, 0, 0],
 ];
+
+// https://github.com/nodejs/node/pull/50825
+export const esmLoadReadFile: Version[] = [
+	[20, 11, 0],
+	[21, 3, 0],
+];

src/utils/transform/transform-dynamic-import.ts

@@ -6,11 +6,8 @@ export const version = '2';
 
 const toEsmFunctionString = ((imported: Record<string, unknown>) => {
 	const d = 'default';
-	const exports = Object.keys(imported);
 	if (
-		exports.length === 1
-		&& exports[0] === d
-		&& imported[d]
+		imported[d]
 		&& typeof imported[d] === 'object'
 		&& '__esModule' in imported[d]
 	) {

tests/specs/smoke.ts

@@ -12,7 +12,7 @@ import { packageTypes } from '../utils/package-types.js';
 const wasmPath = path.resolve('tests/fixtures/test.wasm');
 const wasmPathUrl = pathToFileURL(wasmPath).toString();
 
-export default testSuite(async ({ describe }, { tsx }: NodeApis) => {
+export default testSuite(async ({ describe }, { tsx, supports }: NodeApis) => {
 	describe('Smoke', ({ describe }) => {
 		for (const packageType of packageTypes) {
 			const isCommonJs = packageType === 'commonjs';
@@ -151,7 +151,11 @@ export default testSuite(async ({ describe }, { tsx }: NodeApis) => {
 						expect(p.stdout).toMatch(/\{"importMetaUrl":"file:\/\/\/.+?\/js\/index\.js","__filename":".+?index\.js"\}/);
 						expect(p.stdout).toMatch(/\{"importMetaUrl":"file:\/\/\/.+?\/js\/index\.js\?query=123","__filename":".+?index\.js"\}/);
 					} else {
-						expect(p.stdout).toMatch('"pkgCommonjs":{"default":{"default":1,"named":2}}');
+						expect(p.stdout).toMatch(
+							supports.cjsInterop
+								? '"pkgCommonjs":{"default":{"default":1,"named":2},"named":2}'
+								: '"pkgCommonjs":{"default":{"default":1,"named":2}}',
+						);
 
 						expect(p.stdout).toMatch(/\{"importMetaUrl":"file:\/\/\/.+?\/js\/index\.js"\}/);
 						expect(p.stdout).toMatch(/\{"importMetaUrl":"file:\/\/\/.+?\/js\/index\.js\?query=123"\}/);
@@ -365,7 +369,11 @@ export default testSuite(async ({ describe }, { tsx }: NodeApis) => {
 						expect(p.stdout).toMatch(/\{"importMetaUrl":"file:\/\/\/.+?\/js\/index\.js","__filename":".+?index\.js"\}/);
 						expect(p.stdout).toMatch(/\{"importMetaUrl":"file:\/\/\/.+?\/js\/index\.js\?query=123","__filename":".+?index\.js"\}/);
 					} else {
-						expect(p.stdout).toMatch('"pkgCommonjs":{"default":{"default":1,"named":2}}');
+						expect(p.stdout).toMatch(
+							supports.cjsInterop
+								? '"pkgCommonjs":{"default":{"default":1,"named":2},"named":2}'
+								: '"pkgCommonjs":{"default":{"default":1,"named":2}}',
+						);
 
 						expect(p.stdout).toMatch(/\{"importMetaUrl":"file:\/\/\/.+?\/js\/index\.js"\}/);
 						expect(p.stdout).toMatch(/\{"importMetaUrl":"file:\/\/\/.+?\/js\/index\.js\?query=123"\}/);

tests/utils/tsx.ts

@@ -4,6 +4,7 @@ import {
 	isFeatureSupported,
 	moduleRegister,
 	testRunnerGlob,
+	esmLoadReadFile,
 	type Version,
 } from '../../src/utils/node-features.js';
 import { getNode } from './get-node.js';
@@ -54,6 +55,8 @@ export const createNode = async (
 
 		// https://nodejs.org/docs/latest-v18.x/api/cli.html#--test
 		cliTestFlag: isFeatureSupported([[18, 1, 0]], versionParsed),
+
+		cjsInterop: isFeatureSupported(esmLoadReadFile, versionParsed),
 	};
 	const hookFlag = supports.moduleRegister ? '--import' : '--loader';