module: move helpers out of cjs loader

Author: GeoffreyBooth

lib/internal/modules/cjs/loader.js

@@ -68,7 +68,7 @@ const cjsParseCache = new SafeWeakMap();
 
 // Set first due to cycle with ESM loader functions.
 module.exports = {
-  wrapSafe, Module, toRealPath, readPackageScope, cjsParseCache,
+  wrapSafe, Module, readPackageScope, cjsParseCache,
   get hasLoadedAnyUserCJSModule() { return hasLoadedAnyUserCJSModule; },
   initializeCJS,
 };
@@ -88,7 +88,6 @@ const {
 const { internalCompileFunction } = require('internal/vm');
 const assert = require('internal/assert');
 const fs = require('fs');
-const internalFS = require('internal/fs/utils');
 const path = require('path');
 const { sep } = path;
 const { internalModuleStat } = internalBinding('fs');
@@ -106,6 +105,7 @@ const {
   makeRequireFunction,
   normalizeReferrerURL,
   stripBOM,
+  toRealPath,
 } = require('internal/modules/helpers');
 const packageJsonReader = require('internal/modules/package_json_reader');
 const { getOptionValue, getEmbedderOptions } = require('internal/options');
@@ -498,14 +498,6 @@ function tryPackage(requestPath, exts, isMain, originalPath) {
   return actual;
 }
 
-/**
- * Cache for storing resolved real paths of modules.
- * In order to minimize unnecessary lstat() calls, this cache is a list of known-real paths.
- * Set to an empty Map to reset.
- * @type {Map<string, string>}
- */
-const realpathCache = new SafeMap();
-
 /**
  * Check if the file exists and is not a directory if using `--preserve-symlinks` and `isMain` is false, keep symlinks
  * intact, otherwise resolve to the absolute realpath.
@@ -521,17 +513,6 @@ function tryFile(requestPath, isMain) {
   return toRealPath(requestPath);
 }
 
-
-/**
- * Resolves the path of a given `require` specifier, following symlinks.
- * @param {string} requestPath The `require` specifier
- */
-function toRealPath(requestPath) {
-  return fs.realpathSync(requestPath, {
-    [internalFS.realpathCacheKey]: realpathCache,
-  });
-}
-
 /**
  * Given a path, check if the file exists with any of the set extensions.
  * @param {string} basePath The path and filename without extension

lib/internal/modules/helpers.js

@@ -21,6 +21,8 @@ const {
 const { BuiltinModule } = require('internal/bootstrap/realm');
 
 const { validateString } = require('internal/validators');
+const fs = require('fs'); // Import all of `fs` so that it can be monkey-patched.
+const internalFS = require('internal/fs/utils');
 const path = require('path');
 const { pathToFileURL, fileURLToPath, URL } = require('internal/url');
 
@@ -39,6 +41,23 @@ let debug = require('internal/util/debuglog').debuglog('module', (fn) => {
 
 /** @typedef {import('internal/modules/cjs/loader.js').Module} Module */
 
+/**
+ * Cache for storing resolved real paths of modules.
+ * In order to minimize unnecessary lstat() calls, this cache is a list of known-real paths.
+ * Set to an empty Map to reset.
+ * @type {Map<string, string>}
+ */
+const realpathCache = new SafeMap();
+/**
+ * Resolves the path of a given `require` specifier, following symlinks.
+ * @param {string} requestPath The `require` specifier
+ */
+function toRealPath(requestPath) {
+  return fs.realpathSync(requestPath, {
+    [internalFS.realpathCacheKey]: realpathCache,
+  });
+}
+
 /** @type {Set<string>} */
 let cjsConditions;
 /**
@@ -310,4 +329,5 @@ module.exports = {
   makeRequireFunction,
   normalizeReferrerURL,
   stripBOM,
+  toRealPath,
 };

lib/internal/modules/run_main.js

@@ -15,12 +15,13 @@ function resolveMainPath(main) {
   // Note extension resolution for the main entry point can be deprecated in a
   // future major.
   // Module._findPath is monkey-patchable here.
-  const { Module, toRealPath } = require('internal/modules/cjs/loader');
+  const { Module } = require('internal/modules/cjs/loader');
   let mainPath = Module._findPath(path.resolve(main), null, true);
   if (!mainPath) { return; }
 
   const preserveSymlinksMain = getOptionValue('--preserve-symlinks-main');
   if (!preserveSymlinksMain) {
+    const { toRealPath } = require('internal/modules/helpers');
     mainPath = toRealPath(mainPath);
   }