module: refactor commonjs typescript loader

This commit refactors the CommonJS loader to remove TypeScript-specific extensions from the require.extensions object for compatibility with libraries that depended on it to initialize extenal TypeScript loaders. PR-URL: #58657 Refs: nodejs/typescript#37 Reviewed-By: Matteo Collina <matteo.collina@gmail.com> Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com> Reviewed-By: Pietro Marchini <pietro.marchini94@gmail.com> Reviewed-By: Xuguang Mei <meixuguang@gmail.com>
nodejs · github-actions · Jun 9, 2025 · Jun 9, 2025 · Jun 9, 2025 · Jun 9, 2025
commit 45f7d160ed922111d87eb403336f29a6d833f3cb
diff --git a/lib/internal/modules/cjs/loader.js b/lib/internal/modules/cjs/loader.js
@@ -454,17 +454,6 @@ function initializeCJS() {
   // TODO(joyeecheung): deprecate this in favor of a proper hook?
   Module.runMain =
     require('internal/modules/run_main').executeUserEntryPoint;
-
-  const tsEnabled = getOptionValue('--experimental-strip-types');
-  if (tsEnabled) {
-    Module._extensions['.cts'] = loadCTS;
-    Module._extensions['.ts'] = loadTS;
-  }
-  if (getOptionValue('--experimental-require-module')) {
-    if (tsEnabled) {
-      Module._extensions['.mts'] = loadMTS;
-    }
-  }
 }
 
 // Given a module name, and a list of paths to test, returns the first
@@ -670,31 +659,6 @@ function resolveExports(nmPath, request, conditions) {
   }
 }
 
-// We don't cache this in case user extends the extensions.
-function getDefaultExtensions() {
-  let extensions = ObjectKeys(Module._extensions);
-  const tsEnabled = getOptionValue('--experimental-strip-types');
-  if (tsEnabled) {
-    // remove .ts and .cts from the default extensions
-    // to avoid extensionless require of .ts and .cts files.
-    extensions = ArrayPrototypeFilter(extensions, (ext) =>
-      (ext !== '.ts' || Module._extensions['.ts'] !== loadTS) &&
-      (ext !== '.cts' || Module._extensions['.cts'] !== loadCTS),
-    );
-  }
-
-  if (!getOptionValue('--experimental-require-module')) {
-    return extensions;
-  }
-
-  if (tsEnabled) {
-    extensions = ArrayPrototypeFilter(extensions, (ext) =>
-      ext !== '.mts' || Module._extensions['.mts'] !== loadMTS,
-    );
-  }
-  return extensions;
-}
-
 /**
  * Get the absolute path to a module.
  * @param {string} request Relative or absolute file path
@@ -786,7 +750,7 @@ Module._findPath = function(request, paths, isMain, conditions = getCjsCondition
       if (!filename) {
         // Try it with each of the extensions
         if (exts === undefined) {
-          exts = getDefaultExtensions();
+          exts = ObjectKeys(Module._extensions);
         }
         filename = tryExtensions(basePath, exts, isMain);
       }
@@ -795,7 +759,7 @@ Module._findPath = function(request, paths, isMain, conditions = getCjsCondition
     if (!filename && rc === 1) {  // Directory.
       // try it with each of the extensions at "index"
       if (exts === undefined) {
-        exts = getDefaultExtensions();
+        exts = ObjectKeys(Module._extensions);
       }
       filename = tryPackage(basePath, exts, isMain, request);
     }
@@ -1460,12 +1424,6 @@ Module.prototype.load = function(filename) {
 
   const extension = findLongestRegisteredExtension(filename);
 
-  if (getOptionValue('--experimental-strip-types')) {
-    if (StringPrototypeEndsWith(filename, '.mts') && !Module._extensions['.mts']) {
-      throw new ERR_REQUIRE_ESM(filename, true);
-    }
-  }
-
   Module._extensions[extension](this, filename);
   this.loaded = true;
 
@@ -1777,55 +1735,6 @@ function loadSource(mod, filename, formatFromNode) {
   return { source: mod[kModuleSource], format: mod[kFormat] };
 }
 
-/**
- * Built-in handler for `.mts` files.
- * @param {Module} mod CJS module instance
- * @param {string} filename The file path of the module
- */
-function loadMTS(mod, filename) {
-  const loadResult = loadSource(mod, filename, 'module-typescript');
-  mod._compile(loadResult.source, filename, loadResult.format);
-}
-
-/**
- * Built-in handler for `.cts` files.
- * @param {Module} module CJS module instance
- * @param {string} filename The file path of the module
- */
-function loadCTS(module, filename) {
-  const loadResult = loadSource(module, filename, 'commonjs-typescript');
-  module._compile(loadResult.source, filename, loadResult.format);
-}
-
-/**
- * Built-in handler for `.ts` files.
- * @param {Module} module CJS module instance
- * @param {string} filename The file path of the module
- */
-function loadTS(module, filename) {
-  const pkg = packageJsonReader.getNearestParentPackageJSON(filename);
-  const typeFromPjson = pkg?.data.type;
-
-  let format;
-  if (typeFromPjson === 'module') {
-    format = 'module-typescript';
-  } else if (typeFromPjson === 'commonjs') {
-    format = 'commonjs-typescript';
-  } else {
-    format = 'typescript';
-  }
-  const loadResult = loadSource(module, filename, format);
-
-  // Function require shouldn't be used in ES modules when require(esm) is disabled.
-  if (typeFromPjson === 'module' && !getOptionValue('--experimental-require-module')) {
-    const err = getRequireESMError(module, pkg, loadResult.source, filename);
-    throw err;
-  }
-
-  module[kFormat] = loadResult.format;
-  module._compile(loadResult.source, filename, loadResult.format);
-};
-
 function reconstructErrorStack(err, parentPath, parentSource) {
   const errLine = StringPrototypeSplit(
     StringPrototypeSlice(err.stack, StringPrototypeIndexOf(
@@ -1879,6 +1788,7 @@ function getRequireESMError(mod, pkg, content, filename) {
  */
 Module._extensions['.js'] = function(module, filename) {
   let format, pkg;
+  const tsEnabled = getOptionValue('--experimental-strip-types');
   if (StringPrototypeEndsWith(filename, '.cjs')) {
     format = 'commonjs';
   } else if (StringPrototypeEndsWith(filename, '.mjs')) {
@@ -1889,10 +1799,25 @@ Module._extensions['.js'] = function(module, filename) {
     if (typeFromPjson === 'module' || typeFromPjson === 'commonjs' || !typeFromPjson) {
       format = typeFromPjson;
     }
+  } else if (StringPrototypeEndsWith(filename, '.mts') && tsEnabled) {
+    format = 'module-typescript';
+  } else if (StringPrototypeEndsWith(filename, '.cts') && tsEnabled) {
+    format = 'commonjs-typescript';
+  } else if (StringPrototypeEndsWith(filename, '.ts') && tsEnabled) {
+    pkg = packageJsonReader.getNearestParentPackageJSON(filename);
+    const typeFromPjson = pkg?.data.type;
+    if (typeFromPjson === 'module') {
+      format = 'module-typescript';
+    } else if (typeFromPjson === 'commonjs') {
+      format = 'commonjs-typescript';
+    } else {
+      format = 'typescript';
+    }
   }
   const { source, format: loadedFormat } = loadSource(module, filename, format);
   // Function require shouldn't be used in ES modules when require(esm) is disabled.
-  if (loadedFormat === 'module' && !getOptionValue('--experimental-require-module')) {
+  if ((loadedFormat === 'module' || loadedFormat === 'module-typescript') &&
+    !getOptionValue('--experimental-require-module')) {
     const err = getRequireESMError(module, pkg, source, filename);
     throw err;
   }