cjs/loader.js WIP

Author: GeoffreyBooth

lib/internal/modules/cjs/loader.js

@@ -155,6 +155,11 @@ let requireDepth = 0;
 let isPreloading = false;
 let statCache = null;
 
+/**
+ * Our internal implementation of `require`.
+ * @param {Module} module Parent module of what is being required
+ * @param {string} id Specifier of the child module being imported
+ */
 function internalRequire(module, id) {
   validateString(id, 'id');
   if (id === '') {
@@ -169,6 +174,10 @@ function internalRequire(module, id) {
   }
 }
 
+/**
+ * Get a path's properties, using an in-memory cache to minimize lookups.
+ * @param {string} filename Absolute path to the file
+ */
 function stat(filename) {
   filename = path.toNamespacedPath(filename);
   if (statCache !== null) {
@@ -195,24 +204,45 @@ ObjectDefineProperty(Module, '_stat', {
   configurable: true,
 });
 
+/**
+ * Update the parent's children array with the child module.
+ * @param {Module} parent Module requiring the children
+ * @param {Module} child Module being required
+ * @param {boolean} scan Add the child to the parent's children if not already present
+ */
 function updateChildren(parent, child, scan) {
   const children = parent?.children;
   if (children && !(scan && ArrayPrototypeIncludes(children, child))) { ArrayPrototypePush(children, child); }
 }
 
+/**
+ * Tell the watch mode that a module was required.
+ * @param {string} filename Absolute path of the module
+ */
 function reportModuleToWatchMode(filename) {
   if (shouldReportRequiredModules() && process.send) {
     process.send({ 'watch:require': [filename] });
   }
 }
 
+/**
+ * Tell the watch mode that a module was not found.
+ * @param {string} basePath The absolute path that errored
+ * @param {string[]} extensions The extensions that were tried
+ */
 function reportModuleNotFoundToWatchMode(basePath, extensions) {
   if (shouldReportRequiredModules() && process.send) {
     process.send({ 'watch:require': ArrayPrototypeMap(extensions, (ext) => path.resolve(`${basePath}${ext}`)) });
   }
 }
 
+/** @type {Map<Module, Module>} */
 const moduleParentCache = new SafeWeakMap();
+/**
+ * Create a new module instance.
+ * @param {string} id
+ * @param {Module} parent
+ */
 function Module(id = '', parent) {
   this.id = id;
   this.path = path.dirname(id);
@@ -235,16 +265,24 @@ function Module(id = '', parent) {
   this[require_private_symbol] = internalRequire;
 }
 
+/** @type {Record<string, Module>} */
 Module._cache = { __proto__: null };
+/** @type {Record<string, string>} */
 Module._pathCache = { __proto__: null };
+/** @type {Record<string, (module: Module, filename: string) => void>} */
 Module._extensions = { __proto__: null };
+/** @type {string[]} */
 let modulePaths = [];
+/** @type {string[]} */
 Module.globalPaths = [];
 
 let patched = false;
 
-// eslint-disable-next-line func-style
-let wrap = function(script) {
+/**
+ * Add the CommonJS wrapper around a module's source code.
+ * @param {string} script Module source code
+ */
+let wrap = function(script) { // eslint-disable-line func-style
   return Module.wrapper[0] + script + Module.wrapper[1];
 };
 
@@ -295,10 +333,17 @@ const isPreloadingDesc = { get() { return isPreloading; } };
 ObjectDefineProperty(Module.prototype, 'isPreloading', isPreloadingDesc);
 ObjectDefineProperty(BuiltinModule.prototype, 'isPreloading', isPreloadingDesc);
 
+/**
+ * Get the parent of the current module from our cache.
+ */
 function getModuleParent() {
   return moduleParentCache.get(this);
 }
 
+/**
+ * Set the parent of the current module in our cache.
+ * @param {Module} value
+ */
 function setModuleParent(value) {
   moduleParentCache.set(this, value);
 }
@@ -325,7 +370,10 @@ ObjectDefineProperty(Module.prototype, 'parent', {
 Module._debug = pendingDeprecate(debug, 'Module._debug is deprecated.', 'DEP0077');
 Module.isBuiltin = BuiltinModule.isBuiltin;
 
-// This function is called during pre-execution, before any user code is run.
+/**
+ * Prepare to run CommonJS code.
+ * This function is called during pre-execution, before any user code is run.
+ */
 function initializeCJS() {
   // This need to be done at runtime in case --expose-internals is set.
   const builtinModules = BuiltinModule.getCanBeRequiredByUsersWithoutSchemeList();
@@ -373,6 +421,11 @@ ObjectDefineProperty(Module, '_readPackage', {
   configurable: true,
 });
 
+/**
+ * Get the nearest parent package.json file from a given path.
+ * Return the package.json data and the path to the package.json file, or false.
+ * @param {string} checkPath The path to start searching from.
+ */
 function readPackageScope(checkPath) {
   const rootSeparatorIndex = StringPrototypeIndexOf(checkPath, sep);
   let separatorIndex;
@@ -397,6 +450,13 @@ function readPackageScope(checkPath) {
   return false;
 }
 
+/**
+ * Try to load a specifier as a package.
+ * @param {string} requestPath The path to what we are trying to load
+ * @param {string[]} exts File extensions to try appending in order to resolve the file
+ * @param {boolean} isMain Whether the file is the main entry point of the app
+ * @param {string} originalPath The specifier passed to `require`
+ */
 function tryPackage(requestPath, exts, isMain, originalPath) {
   const pkg = _readPackage(requestPath).main;
 
@@ -553,9 +613,10 @@ function resolveExports(nmPath, request) {
 }
 
 /**
- * @param {string} request a relative or absolute file path
- * @param {Array<string>} paths file system directories to search as file paths
- * @param {boolean} isMain if the request is the main app entry point
+ * Get the absolute path to a module.
+ * @param {string} request Relative or absolute file path
+ * @param {Array<string>} paths Folders to search as file paths
+ * @param {boolean} isMain Whether the request is the main app entry point
  * @returns {string | false}
  */
 Module._findPath = function(request, paths, isMain) {
@@ -851,13 +912,17 @@ function getExportsForCircularRequire(module) {
   return module.exports;
 }
 
-// Check the cache for the requested file.
-// 1. If a module already exists in the cache: return its exports object.
-// 2. If the module is native: call
-//    `BuiltinModule.prototype.compileForPublicLoader()` and return the exports.
-// 3. Otherwise, create a new module for the file and save it to the cache.
-//    Then have it load  the file contents before returning its exports
-//    object.
+/**
+ * Load a module from cache if it exists, otherwise create a new module instance.
+ * 1. If a module already exists in the cache: return its exports object.
+ * 2. If the module is native: call
+ *    `BuiltinModule.prototype.compileForPublicLoader()` and return the exports.
+ * 3. Otherwise, create a new module for the file and save it to the cache.
+ *    Then have it load the file contents before returning its exports object.
+ * @param {string} request Specifier of module to load via `require`
+ * @param {string} parent Absolute path of the module importing the child
+ * @param {boolean} isMain Whether the module is the main entry point
+ */
 Module._load = function(request, parent, isMain) {
   let relResolveCacheIdentifier;
   if (parent) {