module: fix strip-types interaction with detect-module

Author: marco-ippolito

lib/internal/modules/esm/get_format.js

@@ -164,7 +164,8 @@ function getFileProtocolModuleFormat(url, context = { __proto__: null }, ignoreE
         const { tsParse } = require('internal/modules/helpers');
         const parsedSource = tsParse(source);
         const detectedFormat = detectModuleFormat(parsedSource, url);
-        const format = detectedFormat ? `${detectedFormat}-typescript` : 'commonjs-typescript';
+        // When source is undefined, default to module-typescript.
+        const format = detectedFormat ? `${detectedFormat}-typescript` : 'module-typescript';
         if (format === 'module-typescript' && foundPackageJson) {
           // This module has a .js extension, a package.json with no `type` field, and ESM syntax.
           // Warn about the missing `type` field so that the user can avoid the performance penalty of detection.

lib/internal/modules/helpers.js

@@ -307,10 +307,15 @@ function lazyLoadTSParser() {
   return parseTS;
 }
 
+/**
+ * Performs type-stripping to TypeScript source code.
+ * @param {string} source TypeScript code to parse.
+ * @returns {string} JavaScript code.
+ */
 function tsParse(source) {
-  if (!source || typeof source !== 'string') { return; }
+  if (!source || typeof source !== 'string') { return ''; }
   const transformSync = lazyLoadTSParser();
-  const { code } = transformSync(source);
+  const { code } = transformSync(source, { __proto__: null, mode: 'strip-only' });
   return code;
 }
 

lib/internal/modules/run_main.js

@@ -84,7 +84,7 @@ function shouldUseESMLoader(mainPath) {
   if (getOptionValue('--experimental-strip-types')) {
     // This ensures that --experimental-default-type=commonjs and .mts files are treated as commonjs
     if (getOptionValue('--experimental-default-type') === 'commonjs') { return false; }
-    if (mainPath && StringPrototypeEndsWith(mainPath, '.cts')) { return false; }
+    if (!mainPath || StringPrototypeEndsWith(mainPath, '.cts')) { return false; }
     // This will likely change in the future to start with commonjs loader by default
     if (mainPath && StringPrototypeEndsWith(mainPath, '.mts')) { return true; }
   }

test/es-module/test-typescript-commonjs.mjs

@@ -118,7 +118,7 @@ test('execute a .cts file importing a .mts file export', async () => {
   strictEqual(result.code, 0);
 });
 
-test('expect failure of a .cts file with default type module', async () => {
+test('execute a .cts file with default type module', async () => {
   const result = await spawnPromisified(process.execPath, [
     '--experimental-strip-types',
     '--experimental-default-type=module', // Keeps working with commonjs

test/es-module/test-typescript-eval.mjs

@@ -4,7 +4,6 @@ import { test } from 'node:test';
 
 test('eval TypeScript ESM syntax', async () => {
   const result = await spawnPromisified(process.execPath, [
-    '--input-type=module',
     '--experimental-strip-types',
     '--eval',
     `import util from 'node:util'
@@ -18,7 +17,6 @@ test('eval TypeScript ESM syntax', async () => {
 
 test('eval TypeScript CommonJS syntax', async () => {
   const result = await spawnPromisified(process.execPath, [
-    '--input-type=commonjs',
     '--experimental-strip-types',
     '--eval',
     `const util = require('node:util');

test/es-module/test-typescript-module.mjs

@@ -28,7 +28,6 @@ test('execute an .mts file importing an .mts file', async () => {
 test('execute an .mts file importing a .ts file', async () => {
   const result = await spawnPromisified(process.execPath, [
     '--experimental-strip-types',
-    '--experimental-default-type=module', // this should fail
     '--no-warnings',
     fixtures.path('typescript/mts/test-import-ts-file.mts'),
   ]);
@@ -42,7 +41,6 @@ test('execute an .mts file importing a .cts file', async () => {
   const result = await spawnPromisified(process.execPath, [
     '--experimental-strip-types',
     '--no-warnings',
-    '--no-warnings',
     fixtures.path('typescript/mts/test-import-commonjs.mts'),
   ]);
 
@@ -95,3 +93,27 @@ test('execute a .ts file from node_modules', async () => {
   strictEqual(result.stdout, '');
   strictEqual(result.code, 1);
 });
+
+test('execute an empty .ts file', async () => {
+  const result = await spawnPromisified(process.execPath, [
+    '--experimental-strip-types',
+    '--no-warnings',
+    fixtures.path('typescript/ts/test-empty-file.ts'),
+  ]);
+
+  strictEqual(result.stderr, '');
+  strictEqual(result.stdout, '');
+  strictEqual(result.code, 0);
+});
+
+test('execute .ts file importing a module', async () => {
+  const result = await spawnPromisified(process.execPath, [
+    '--experimental-strip-types',
+    '--no-warnings',
+    fixtures.path('typescript/ts/test-import-fs.ts'),
+  ]);
+
+  strictEqual(result.stderr, '');
+  strictEqual(result.stdout, 'Hello, TypeScript!\n');
+  strictEqual(result.code, 0);
+});

test/es-module/test-typescript.mjs

@@ -17,7 +17,6 @@ test('execute a TypeScript file', async () => {
 test('execute a TypeScript file with imports', async () => {
   const result = await spawnPromisified(process.execPath, [
     '--experimental-strip-types',
-    '--experimental-default-type=module',
     '--no-warnings',
     fixtures.path('typescript/ts/test-import-foo.ts'),
   ]);
@@ -30,7 +29,6 @@ test('execute a TypeScript file with imports', async () => {
 test('execute a TypeScript file with node_modules', async () => {
   const result = await spawnPromisified(process.execPath, [
     '--experimental-strip-types',
-    '--experimental-default-type=module',
     '--no-warnings',
     fixtures.path('typescript/ts/test-typescript-node-modules.ts'),
   ]);
@@ -43,7 +41,6 @@ test('execute a TypeScript file with node_modules', async () => {
 test('expect error when executing a TypeScript file with imports with no extensions', async () => {
   const result = await spawnPromisified(process.execPath, [
     '--experimental-strip-types',
-    '--experimental-default-type=module',
     fixtures.path('typescript/ts/test-import-no-extension.ts'),
   ]);
 
@@ -101,7 +98,6 @@ test('execute a TypeScript file with type definition', async () => {
 test('execute a TypeScript file with type definition but no type keyword', async () => {
   const result = await spawnPromisified(process.execPath, [
     '--experimental-strip-types',
-    '--experimental-default-type=module',
     fixtures.path('typescript/ts/test-import-no-type-keyword.ts'),
   ]);
 
@@ -124,7 +120,6 @@ test('execute a TypeScript file with CommonJS syntax', async () => {
 test('execute a TypeScript file with ES module syntax', async () => {
   const result = await spawnPromisified(process.execPath, [
     '--experimental-strip-types',
-    '--experimental-default-type=module',
     '--no-warnings',
     fixtures.path('typescript/ts/test-module-typescript.ts'),
   ]);
@@ -159,7 +154,6 @@ test('expect stack trace of a TypeScript file to be correct', async () => {
 
 test('execute CommonJS TypeScript file from node_modules with require-module', async () => {
   const result = await spawnPromisified(process.execPath, [
-    '--experimental-default-type=module',
     '--experimental-strip-types',
     fixtures.path('typescript/ts/test-import-ts-node-modules.ts'),
   ]);
@@ -218,7 +212,6 @@ test('execute a TypeScript file with CommonJS syntax requiring .mts with require
 test('execute a TypeScript file with CommonJS syntax requiring .mts with require-module', async () => {
   const result = await spawnPromisified(process.execPath, [
     '--experimental-strip-types',
-    '--experimental-default-type=commonjs',
     '--no-warnings',
     fixtures.path('typescript/ts/test-require-cts.ts'),
   ]);

test/fixtures/typescript/ts/test-empty-file.ts

@@ -0,0 +1 @@
+

test/fixtures/typescript/ts/test-import-fs.ts

@@ -0,0 +1,2 @@
+import fs from 'fs';
+console.log('Hello, TypeScript!');