module: handle .mjs in .js handler in CommonJS

This refactors the CommonJS loading a bit to create a center point that handles source loading (`loadSource`) and make format detection more consistent to pave the way for future synchronous hooks. - Handle .mjs in the .js handler, similar to how .cjs has been handled. - Generate the legacy ERR_REQUIRE_ESM in a getRequireESMError() for require(esm) handling (when it's disabled). PR-URL: #55590 Backport-PR-URL: #59504 Refs: nodejs/loaders#198 Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com> Reviewed-By: Marco Ippolito <marcoippolito54@gmail.com> Reviewed-By: Juan José Arboleda <soyjuanarbol@gmail.com> Refs: #52697

Author: joyeecheung

lib/internal/modules/cjs/loader.js

@@ -101,6 +101,9 @@ const kIsMainSymbol = Symbol('kIsMainSymbol');
 const kIsCachedByESMLoader = Symbol('kIsCachedByESMLoader');
 const kRequiredModuleSymbol = Symbol('kRequiredModuleSymbol');
 const kIsExecuting = Symbol('kIsExecuting');
+
+const kFormat = Symbol('kFormat');
+
 // Set first due to cycle with ESM loader functions.
 module.exports = {
  kModuleSource,
@@ -438,10 +441,6 @@ function initializeCJS() {
  // TODO(joyeecheung): deprecate this in favor of a proper hook?
  Module.runMain =
  require('internal/modules/run_main').executeUserEntryPoint;
-
- if (getOptionValue('--experimental-require-module')) {
- Module._extensions['.mjs'] = loadESMFromCJS;
- }
 }
 
 // Given a module name, and a list of paths to test, returns the first
@@ -651,14 +650,7 @@ function resolveExports(nmPath, request) {
 // We don't cache this in case user extends the extensions.
 function getDefaultExtensions() {
  const extensions = ObjectKeys(Module._extensions);
- if (!getOptionValue('--experimental-require-module')) {
- return extensions;
- }
- // If the .mjs extension is added by --experimental-require-module,
- // remove it from the supported default extensions to maintain
- // compatibility.
- // TODO(joyeecheung): allow both .mjs and .cjs?
- return ArrayPrototypeFilter(extensions, (ext) => ext !== '.mjs' || Module._extensions['.mjs'] !== loadESMFromCJS);
+ return extensions;
 }
 
 /**
@@ -1270,10 +1262,6 @@ Module.prototype.load = function(filename) {
  this.paths = Module._nodeModulePaths(path.dirname(filename));
 
  const extension = findLongestRegisteredExtension(filename);
- // allow .mjs to be overridden
- if (StringPrototypeEndsWith(filename, '.mjs') && !Module._extensions['.mjs']) {
- throw new ERR_REQUIRE_ESM(filename, true);
- }
 
  Module._extensions[extension](this, filename);
  this.loaded = true;
@@ -1309,9 +1297,10 @@ let requireModuleWarningMode;
  * Resolve and evaluate it synchronously as ESM if it's ESM.
  * @param {Module} mod CJS module instance
  * @param {string} filename Absolute path of the file.
+ * @param {string} format Format of the module. If it had types, this would be what it is after type-stripping.
+ * @param {string} source Source the module. If it had types, this would have the type stripped.
  */
-function loadESMFromCJS(mod, filename) {
- const source = getMaybeCachedSource(mod, filename);
+function loadESMFromCJS(mod, filename, format, source) {
  const cascadedLoader = require('internal/modules/esm/loader').getOrInitializeCascadedLoader();
  const isMain = mod[kIsMainSymbol];
  if (isMain) {
@@ -1487,7 +1476,9 @@ function wrapSafe(filename, content, cjsModuleInstance, format) {
  * `exports`) to the file. Returns exception, if any.
  * @param {string} content The source code of the module
  * @param {string} filename The file path of the module
- * @param {'module'|'commonjs'|undefined} format Intended format of the module.
+ * @param {
+ * 'module'|'commonjs'|'commonjs-typescript'|'module-typescript'
+ * } format Intended format of the module.
  */
 Module.prototype._compile = function(content, filename, format) {
  let moduleURL;
@@ -1509,9 +1500,7 @@ Module.prototype._compile = function(content, filename, format) {
  }
 
  if (format === 'module') {
- // Pass the source into the .mjs extension handler indirectly through the cache.
- this[kModuleSource] = content;
- loadESMFromCJS(this, filename);
+ loadESMFromCJS(this, filename, format, content);
  return;
  }
 
@@ -1539,22 +1528,72 @@ Module.prototype._compile = function(content, filename, format) {
 
 /**
  * Get the source code of a module, using cached ones if it's cached.
+ * After this returns, mod[kFormat], mod[kModuleSource] and mod[kURL] will be set.
  * @param {Module} mod Module instance whose source is potentially already cached.
  * @param {string} filename Absolute path to the file of the module.
- * @returns {string}
+ * @returns {{source: string, format?: string}}
  */
-function getMaybeCachedSource(mod, filename) {
- // If already analyzed the source, then it will be cached.
- let content;
- if (mod[kModuleSource] !== undefined) {
- content = mod[kModuleSource];
+function loadSource(mod, filename, formatFromNode) {
+ if (formatFromNode !== undefined) {
+ mod[kFormat] = formatFromNode;
+ }
+ const format = mod[kFormat];
+
+ let source = mod[kModuleSource];
+ if (source !== undefined) {
  mod[kModuleSource] = undefined;
  } else {
  // TODO(joyeecheung): we can read a buffer instead to speed up
  // compilation.
- content = fs.readFileSync(filename, 'utf8');
+ source = fs.readFileSync(filename, 'utf8');
+ }
+ return { source, format };
+}
+
+function reconstructErrorStack(err, parentPath, parentSource) {
+ const errLine = StringPrototypeSplit(
+ StringPrototypeSlice(err.stack, StringPrototypeIndexOf(
+ err.stack, ' at ')), '\n', 1)[0];
+ const { 1: line, 2: col } =
+ RegExpPrototypeExec(/(\d+):(\d+)\)/, errLine) || [];
+ if (line && col) {
+ const srcLine = StringPrototypeSplit(parentSource, '\n')[line - 1];
+ const frame = `${parentPath}:${line}\n${srcLine}\n${StringPrototypeRepeat(' ', col - 1)}^\n`;
+ setArrowMessage(err, frame);
+ }
+}
+
+/**
+ * Generate the legacy ERR_REQUIRE_ESM for the cases where require(esm) is disabled.
+ * @param {Module} mod The module being required.
+ * @param {undefined|object} pkg Data of the nearest package.json of the module.
+ * @param {string} content Source code of the module.
+ * @param {string} filename Filename of the module
+ * @returns {Error}
+ */
+function getRequireESMError(mod, pkg, content, filename) {
+ // This is an error path because `require` of a `.js` file in a `"type": "module"` scope is not allowed.
+ const parent = mod[kModuleParent];
+ const parentPath = parent?.filename;
+ const packageJsonPath = pkg?.path ? path.resolve(pkg.path, 'package.json') : null;
+ const usesEsm = containsModuleSyntax(content, filename);
+ const err = new ERR_REQUIRE_ESM(filename, usesEsm, parentPath,
+ packageJsonPath);
+ // Attempt to reconstruct the parent require frame.
+ const parentModule = Module._cache[parentPath];
+ if (parentModule) {
+ let parentSource;
+ try {
+ ({ source: parentSource } = loadSource(parentModule, parentPath));
+ } catch {
+ // Continue regardless of error.
+ }
+ if (parentSource) {
+ // TODO(joyeecheung): trim off internal frames from the stack.
+ reconstructErrorStack(err, parentPath, parentSource);
+ }
  }
- return content;
+ return err;
 }
 
 /**
@@ -1563,57 +1602,25 @@ function getMaybeCachedSource(mod, filename) {
  * @param {string} filename The file path of the module
  */
 Module._extensions['.js'] = function(module, filename) {
- // If already analyzed the source, then it will be cached.
- const content = getMaybeCachedSource(module, filename);
-
- let format;
- if (StringPrototypeEndsWith(filename, '.js')) {
- const pkg = packageJsonReader.readPackageScope(filename) || { __proto__: null };
- // Function require shouldn't be used in ES modules.
- if (pkg.data?.type === 'module') {
- if (getOptionValue('--experimental-require-module')) {
- module._compile(content, filename, 'module');
- return;
- }
-
- // This is an error path because `require` of a `.js` file in a `"type": "module"` scope is not allowed.
- const parent = module[kModuleParent];
- const parentPath = parent?.filename;
- const packageJsonPath = path.resolve(pkg.path, 'package.json');
- const usesEsm = containsModuleSyntax(content, filename);
- const err = new ERR_REQUIRE_ESM(filename, usesEsm, parentPath,
- packageJsonPath);
- // Attempt to reconstruct the parent require frame.
- if (Module._cache[parentPath]) {
- let parentSource;
- try {
- parentSource = fs.readFileSync(parentPath, 'utf8');
- } catch {
- // Continue regardless of error.
- }
- if (parentSource) {
- const errLine = StringPrototypeSplit(
- StringPrototypeSlice(err.stack, StringPrototypeIndexOf(
- err.stack, ' at ')), '\n', 1)[0];
- const { 1: line, 2: col } =
- RegExpPrototypeExec(/(\d+):(\d+)\)/, errLine) || [];
- if (line && col) {
- const srcLine = StringPrototypeSplit(parentSource, '\n')[line - 1];
- const frame = `${parentPath}:${line}\n${srcLine}\n${
- StringPrototypeRepeat(' ', col - 1)}^\n`;
- setArrowMessage(err, frame);
- }
- }
- }
- throw err;
- } else if (pkg.data?.type === 'commonjs') {
- format = 'commonjs';
- }
- } else if (StringPrototypeEndsWith(filename, '.cjs')) {
+ let format, pkg;
+ if (StringPrototypeEndsWith(filename, '.cjs')) {
  format = 'commonjs';
+ } else if (StringPrototypeEndsWith(filename, '.mjs')) {
+ format = 'module';
+ } else if (StringPrototypeEndsWith(filename, '.js')) {
+ pkg = packageJsonReader.readPackageScope(filename) || { __proto__: null };
+ const typeFromPjson = pkg.data?.type;
+ if (typeFromPjson === 'module' || typeFromPjson === 'commonjs' || !typeFromPjson) {
+ format = typeFromPjson;
+ }
  }
-
- module._compile(content, filename, format);
+ 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')) {
+ const err = getRequireESMError(module, pkg, source, filename);
+ throw err;
+ }
+ module._compile(source, filename, loadedFormat);
 };
 
 /**