fix(esm/api): tsImport() to parse CJS exports

fixes #575

Author: privatenumber

src/esm/hook/load.ts

@@ -10,7 +10,6 @@ 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';
 
@@ -69,20 +68,35 @@ export const load: LoadHook = async (
 		loaded.format === 'commonjs'
 		&& isFeatureSupported(esmLoadReadFile)
 		&& loaded.responseURL?.startsWith('file:') // Could be data:
+		&& !filePath.endsWith('.cjs') // CJS syntax doesn't need to be transformed for interop
 	) {
-		const code = await readFile(new URL(url), 'utf8');
-		const [, exports] = parseEsm(code);
-		if (exports.length > 0) {
-			const cjsExports = `module.exports={${
-				exports.map(exported => exported.n).filter(name => name !== 'default').join(',')
-			}}`;
-			const parameters = new URLSearchParams({ filePath });
-			if (urlNamespace) {
-				parameters.set('namespace', urlNamespace);
-			}
-			loaded.responseURL = `data:text/javascript,${encodeURIComponent(cjsExports)}?${parameters.toString()}`;
-		}
+		/**
+		 * es or cjs module lexer unfortunately cannot be used because it doesn't support
+		 * typescript syntax
+		 *
+		 * While the full code is transformed, only the exports are used for parsing.
+		 * In fact, the code can't even run because imports cannot be resolved relative
+		 * from the data: URL.
+		 *
+		 * TODO: extract exports only
+		 */
+		const transformed = await transform(
+			await readFile(new URL(url), 'utf8'),
+			filePath,
+			{
+				format: 'cjs',
 
+				// CJS Annotations for Node
+				platform: 'node',
+				// TODO: disable source maps
+			},
+		);
+
+		const parameters = new URLSearchParams({ filePath });
+		if (urlNamespace) {
+			parameters.set('namespace', urlNamespace);
+		}
+		loaded.responseURL = `data:text/javascript,${encodeURIComponent(transformed.code)}?${parameters.toString()}`;
 		return loaded;
 	}
 

src/utils/debug.ts

@@ -4,7 +4,10 @@ import { writeSync } from 'node:fs';
 export const log = (
 	...args: any[]
 ) => {
-	writeSync(1, `${inspect(args, { colors: true })}\n\n`);
+	writeSync(
+		1,
+		`${args.map(argument => inspect(argument, { colors: true })).join(' ')}\n\n`,
+	);
 };
 
 export const time = <T extends (...args: any[]) => unknown>(

tests/specs/api.ts

@@ -23,7 +23,9 @@ const tsFiles = {
 	export const foo = \`foo \${bar}\` as string
 	export const async = setTimeout(10).then(() => require('./async')).catch((error) => error);
 	`,
-	'cts.cts': 'export const cts = \'cts\' as string',
+	'exports-no.cts': 'console.log("cts loaded" as string)',
+	'exports-yes.cts': 'module.exports.cts = require("./esm-syntax.js").default as string',
+	'esm-syntax.js': 'export default "cts export"',
 	'bar.ts': 'export type A = 1; export { bar } from "pkg"',
 	'async.ts': 'export default "async"',
 	'node_modules/pkg': {
@@ -508,7 +510,10 @@ export default testSuite(({ describe }, node: NodeApis) => {
 							const { message } = await tsImport('./file.ts', import.meta.url);
 							console.log(message);
 
-							const cts = await tsImport('./cts.cts', import.meta.url).then(m => m.cts, err => err.constructor.name);
+							// Loads cts vis CJS namespace even if there are no exports
+							await tsImport('./exports-no.cts', import.meta.url).catch((error) => console.log(error.constructor.name))
+
+							const cts = await tsImport('./exports-yes.cts', import.meta.url).then(m => m.cts, err => err.constructor.name);
 							console.log(cts);
 
 							const { message: message2 } = await tsImport('./file.ts?with-query', import.meta.url);
@@ -528,9 +533,9 @@ export default testSuite(({ describe }, node: NodeApis) => {
 						});
 
 						if (node.supports.cjsInterop) {
-							expect(stdout).toMatch(/Fails as expected 1\nfoo bar file\.ts\?tsx-namespace=\d+\ncts\nfoo bar file\.ts\?with-query=&tsx-namespace=\d+\nFails as expected 2/);
+							expect(stdout).toMatch(/Fails as expected 1\nfoo bar file\.ts\?tsx-namespace=\d+\ncts loaded\ncts export\nfoo bar file\.ts\?with-query=&tsx-namespace=\d+\nFails as expected 2/);
 						} else {
-							expect(stdout).toMatch(/Fails as expected 1\nfoo bar file\.ts\?tsx-namespace=\d+\nSyntaxError\nfoo bar file\.ts\?with-query=&tsx-namespace=\d+\nFails as expected 2/);
+							expect(stdout).toMatch(/Fails as expected 1\nfoo bar file\.ts\?tsx-namespace=\d+\nSyntaxError\nSyntaxError\nfoo bar file\.ts\?with-query=&tsx-namespace=\d+\nFails as expected 2/);
 						}
 					});