vfs: replace monkeypatching with self-contained module.registerHooks

Replace 8 monkeypatched internal functions with self-contained resolve
and load hooks using module.registerHooks(). The resolve hook now
handles bare specifiers (node_modules walking + package.json exports
resolution), relative paths, absolute paths, and file: URLs entirely
within VFS. The load hook uses a local format map, eliminating the
problematic esm/formats lazy dependency.

Remove ~140 lines of toggle infrastructure from helpers.js and
package_json_reader.js, reverting them to direct implementations.
Revert esm/resolve.js to use internalBinding('fs') directly.

Author: mcollina

lib/internal/modules/esm/resolve.js

@@ -23,7 +23,8 @@ const {
 } = primordials;
 const assert = require('internal/assert');
 const { BuiltinModule } = require('internal/bootstrap/realm');
-const { toRealPath, internalModuleStat } = require('internal/modules/helpers');
+const { toRealPath } = require('internal/modules/helpers');
+const internalFsBinding = internalBinding('fs');
 const { getOptionValue } = require('internal/options');
 // Do not eagerly grab .manifest, it may be in TDZ
 const { sep, posix: { relative: relativePosixPath }, resolve } = require('path');
@@ -239,7 +240,7 @@ function finalizeResolution(resolved, base, preserveSymlinks) {
     throw err;
   }
 
-  const stats = internalModuleStat(
+  const stats = internalFsBinding.internalModuleStat(
     StringPrototypeEndsWith(path, '/') ? StringPrototypeSlice(path, -1) : path,
   );
 

lib/internal/modules/helpers.js

@@ -56,109 +56,25 @@ let debug = require('internal/util/debuglog').debuglog('module', (fn) => {
  */
 const realpathCache = new SafeMap();
 
-let customToRealPath = null;
-
 /**
- * Default implementation: resolves the path following symlinks.
+ * Resolves the path of a given `require` specifier, following symlinks.
  * @param {string} requestPath The `require` specifier
  * @returns {string}
  */
-function defaultToRealPath(requestPath) {
+function toRealPath(requestPath) {
   return fs.realpathSync(requestPath, {
     [internalFS.realpathCacheKey]: realpathCache,
   });
 }
 
 /**
- * Resolves the path of a given `require` specifier, following symlinks.
- * When a custom override is set (e.g. for VFS), it is called first.
- * @param {string} requestPath The `require` specifier
- * @returns {string}
- */
-function toRealPath(requestPath) {
-  if (customToRealPath !== null) {
-    return customToRealPath(requestPath, defaultToRealPath);
-  }
-  return defaultToRealPath(requestPath);
-}
-
-/**
- * Set a custom toRealPath override (e.g. for VFS-aware resolution).
- * The function receives (requestPath, defaultToRealPath) and should
- * return the resolved real path.
- * @param {Function|null} fn The custom function, or null to reset
- */
-function setCustomToRealPath(fn) {
-  customToRealPath = fn;
-}
-
-let customReadFileSync = null;
-
-/**
- * Default implementation: reads a file from disk.
- * @param {string} path The file path
- * @param {string|object} options Read options
- * @returns {string|Buffer}
- */
-function defaultReadFileSync(path, options) {
-  return fs.readFileSync(path, options);
-}
-
-/**
- * Reads a file, delegating to a custom override when set (e.g. for VFS).
+ * Reads a file from disk.
  * @param {string} path The file path
  * @param {string|object} options Read options
  * @returns {string|Buffer}
  */
 function readFileSync(path, options) {
-  if (customReadFileSync !== null) {
-    return customReadFileSync(path, options, defaultReadFileSync);
-  }
-  return defaultReadFileSync(path, options);
-}
-
-/**
- * Set a custom readFileSync override (e.g. for VFS-aware reading).
- * The function receives (path, options, defaultReadFileSync) and should
- * return the file content.
- * @param {Function|null} fn The custom function, or null to reset
- */
-function setCustomReadFileSync(fn) {
-  customReadFileSync = fn;
-}
-
-const internalFsBinding = internalBinding('fs');
-let customInternalModuleStat = null;
-
-/**
- * Default implementation: calls the C++ internalModuleStat binding.
- * @param {string} path The file path
- * @returns {number} 0 for file, 1 for directory, negative for not found
- */
-function defaultInternalModuleStat(path) {
-  return internalFsBinding.internalModuleStat(path);
-}
-
-/**
- * Checks the stat of a module path, delegating to a custom override when set.
- * @param {string} path The file path
- * @returns {number} 0 for file, 1 for directory, negative for not found
- */
-function internalModuleStat(path) {
-  if (customInternalModuleStat !== null) {
-    return customInternalModuleStat(path, defaultInternalModuleStat);
-  }
-  return defaultInternalModuleStat(path);
-}
-
-/**
- * Set a custom internalModuleStat override (e.g. for VFS-aware stat).
- * The function receives (path, defaultInternalModuleStat) and should
- * return the stat result.
- * @param {Function|null} fn The custom function, or null to reset
- */
-function setCustomInternalModuleStat(fn) {
-  customInternalModuleStat = fn;
+  return fs.readFileSync(path, options);
 }
 
 /** @type {Set<string>} */
@@ -602,15 +518,11 @@ module.exports = {
   getCjsConditionsArray,
   getCompileCacheDir,
   initializeCjsConditions,
-  internalModuleStat,
   loadBuiltinModuleForEmbedder,
   loadBuiltinModule,
   makeRequireFunction,
   normalizeReferrerURL,
   readFileSync,
-  setCustomInternalModuleStat,
-  setCustomReadFileSync,
-  setCustomToRealPath,
   stringify,
   stripBOM,
   toRealPath,

lib/internal/modules/package_json_reader.js

@@ -35,27 +35,6 @@ const { validateString } = require('internal/validators');
  * @typedef {import('typings/internalBinding/modules').SerializedPackageConfig} SerializedPackageConfig
  */
 
-let customRead = null;
-let customGetPackageScopeConfig = null;
-let customGetPackageType = null;
-let customGetNearestParentPackageJSON = null;
-
-function setCustomRead(fn) {
-  customRead = fn;
-}
-
-function setCustomGetPackageScopeConfig(fn) {
-  customGetPackageScopeConfig = fn;
-}
-
-function setCustomGetPackageType(fn) {
-  customGetPackageType = fn;
-}
-
-function setCustomGetNearestParentPackageJSON(fn) {
-  customGetNearestParentPackageJSON = fn;
-}
-
 /**
  * @param {URL['pathname']} path
  * @param {SerializedPackageConfig} contents
@@ -139,14 +118,7 @@ const requiresJSONParse = (value) => (value !== undefined && (value[0] === '[' |
  * }} opts
  * @returns {PackageConfig}
  */
-function read(jsonPath, opts) {
-  if (customRead !== null) {
-    return customRead(jsonPath, opts, defaultRead);
-  }
-  return defaultRead(jsonPath, opts);
-}
-
-function defaultRead(jsonPath, { base, specifier, isESM } = kEmptyObject) {
+function read(jsonPath, { base, specifier, isESM } = kEmptyObject) {
   // This function will be called by both CJS and ESM, so we need to make sure
   // non-null attributes are converted to strings.
   const parsed = modulesBinding.readPackageJSON(
@@ -192,13 +164,6 @@ const deserializedPackageJSONCache = new SafeMap();
  * @returns {undefined | DeserializedPackageConfig}
  */
 function getNearestParentPackageJSON(checkPath) {
-  if (customGetNearestParentPackageJSON !== null) {
-    return customGetNearestParentPackageJSON(checkPath, defaultGetNearestParentPackageJSON);
-  }
-  return defaultGetNearestParentPackageJSON(checkPath);
-}
-
-function defaultGetNearestParentPackageJSON(checkPath) {
   const parentPackageJSONPath = moduleToParentPackageJSONCache.get(checkPath);
   if (parentPackageJSONPath !== undefined) {
     return deserializedPackageJSONCache.get(parentPackageJSONPath);
@@ -224,13 +189,6 @@ function defaultGetNearestParentPackageJSON(checkPath) {
  * @returns {import('typings/internalBinding/modules').PackageConfig} - The package configuration.
  */
 function getPackageScopeConfig(resolved) {
-  if (customGetPackageScopeConfig !== null) {
-    return customGetPackageScopeConfig(resolved, defaultGetPackageScopeConfig);
-  }
-  return defaultGetPackageScopeConfig(resolved);
-}
-
-function defaultGetPackageScopeConfig(resolved) {
   const result = modulesBinding.getPackageScopeConfig(`${resolved}`);
 
   if (ArrayIsArray(result)) {
@@ -260,13 +218,6 @@ function defaultGetPackageScopeConfig(resolved) {
  * @returns {string}
  */
 function getPackageType(url) {
-  if (customGetPackageType !== null) {
-    return customGetPackageType(url, defaultGetPackageType);
-  }
-  return defaultGetPackageType(url);
-}
-
-function defaultGetPackageType(url) {
   const type = modulesBinding.getPackageType(`${url}`);
   return type ?? 'none';
 }
@@ -324,12 +275,12 @@ function getPackageJSONURL(specifier, base) {
     }
   }
 
-  const { internalModuleStat } = require('internal/modules/helpers');
+  const internalFsBinding = internalBinding('fs');
   let packageJSONUrl = new URL(`./node_modules/${packageName}/package.json`, base);
   let packageJSONPath = fileURLToPath(packageJSONUrl);
   let lastPath;
   do {
-    const stat = internalModuleStat(
+    const stat = internalFsBinding.internalModuleStat(
       StringPrototypeSlice(packageJSONPath, 0, packageJSONPath.length - 13),
     );
     // Check for !stat.isDirectory()
@@ -409,8 +360,4 @@ module.exports = {
   getPackageType,
   getPackageJSONURL,
   findPackageJSON,
-  setCustomRead,
-  setCustomGetPackageScopeConfig,
-  setCustomGetPackageType,
-  setCustomGetNearestParentPackageJSON,
 };