module: add support for node:‑prefixed require(…) calls

Fixes: #36098

Co-authored-by: Darshan Sen <raisinten@gmail.com>

doc/api/esm.md

@@ -204,6 +204,10 @@ import _ from 'data:application/json,"world!"';
 added:
   - v14.13.1
   - v12.20.0
+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/37246
+    description: Added `node:` import support to `require(...)`.
 -->
 
 `node:` URLs are supported as an alternative means to load Node.js builtin

doc/api/modules.md

@@ -280,6 +280,12 @@ irrespective of whether or not `./foo` and `./FOO` are the same file.
 ## Core modules
 
 <!--type=misc-->
+<!-- YAML
+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/37246
+    description: Added `node:` import support to `require(...)`.
+-->
 
 Node.js has several modules compiled into the binary. These modules are
 described in greater detail elsewhere in this documentation.
@@ -288,8 +294,13 @@ The core modules are defined within the Node.js source and are located in the
 `lib/` folder.
 
 Core modules are always preferentially loaded if their identifier is
-passed to `require()`. For instance, `require('http')` will always
-return the built in HTTP module, even if there is a file by that name.
+passed to `require()`. For instance, `require('node:http')` will always
+return the built in HTTP module, even if there is a file or `require.cache`
+entry by that name.
+
+```js
+const fs = require('node:fs/promises');
+```
 
 ## Cycles
 
@@ -642,8 +653,19 @@ error.
 
 Adding or replacing entries is also possible. This cache is checked before
 native modules and if a name matching a native module is added to the cache,
-no require call is
-going to receive the native module anymore. Use with care!
+only `node:`-prefixed require calls are going to receive the native module.
+Use with care!
+
+```js
+const assert = require('assert');
+const realFs = require('fs');
+
+const fakeFs = {};
+require.cache.fs = { exports: fakeFs };
+
+assert.strictEqual(require('fs'), fakeFs);
+assert.strictEqual(require('node:fs'), realFs);
+```
 
 #### `require.extensions`
 <!-- YAML

lib/internal/modules/cjs/helpers.js

@@ -34,8 +34,9 @@ const cjsConditions = new SafeSet(['require', 'node', ...userConditions]);
 
 function loadNativeModule(filename, request) {
   const mod = NativeModule.map.get(filename);
-  if (mod) {
+  if (mod?.canBeRequiredByUsers) {
     debug('load native module %s', request);
+    // compileForPublicLoader() throws if mod.canBeRequiredByUsers is false:
     mod.compileForPublicLoader();
     return mod;
   }

lib/internal/modules/cjs/loader.js

@@ -109,7 +109,8 @@ let hasLoadedAnyUserCJSModule = false;
 const {
   ERR_INVALID_ARG_VALUE,
   ERR_INVALID_MODULE_SPECIFIER,
-  ERR_REQUIRE_ESM
+  ERR_REQUIRE_ESM,
+  ERR_UNKNOWN_BUILTIN_MODULE,
 } = require('internal/errors').codes;
 const { validateString } = require('internal/validators');
 const pendingDeprecation = getOptionValue('--pending-deprecation');
@@ -766,6 +767,17 @@ Module._load = function(request, parent, isMain) {
   }
 
   const filename = Module._resolveFilename(request, parent, isMain);
+  if (StringPrototypeStartsWith(filename, 'node:')) {
+    // Slice 'node:' prefix
+    const id = StringPrototypeSlice(filename, 5);
+
+    const module = loadNativeModule(id, request);
+    if (!module?.canBeRequiredByUsers) {
+      throw new ERR_UNKNOWN_BUILTIN_MODULE(filename);
+    }
+
+    return module.exports;
+  }
 
   const cachedModule = Module._cache[filename];
   if (cachedModule !== undefined) {
@@ -837,7 +849,8 @@ Module._load = function(request, parent, isMain) {
 };
 
 Module._resolveFilename = function(request, parent, isMain, options) {
-  if (NativeModule.canBeRequiredByUsers(request)) {
+  if (StringPrototypeStartsWith(request, 'node:') ||
+      NativeModule.canBeRequiredByUsers(request)) {
     return request;
   }
 

lib/internal/modules/esm/translators.js

@@ -282,8 +282,9 @@ translators.set('builtin', async function builtinStrategy(url) {
   debug(`Translating BuiltinModule ${url}`);
   // Slice 'node:' scheme
   const id = StringPrototypeSlice(url, 5);
-  const module = loadNativeModule(id, url, true);
-  if (!StringPrototypeStartsWith(url, 'node:') || !module) {
+  const module = loadNativeModule(id, url);
+  if (!StringPrototypeStartsWith(url, 'node:') ||
+      !module?.canBeRequiredByUsers) {
     throw new ERR_UNKNOWN_BUILTIN_MODULE(url);
   }
   debug(`Loading BuiltinModule ${url}`);

test/es-module/test-esm-dynamic-import.js

@@ -51,6 +51,8 @@ function expectFsNamespace(result) {
 
   expectModuleError(import('node:unknown'),
                     'ERR_UNKNOWN_BUILTIN_MODULE');
+  expectModuleError(import('node:internal/test/binding'),
+                    'ERR_UNKNOWN_BUILTIN_MODULE');
   expectModuleError(import('./not-an-existing-module.mjs'),
                     'ERR_MODULE_NOT_FOUND');
   expectModuleError(import('http://example.com/foo.js'),

test/parallel/test-require-node-prefix.js

@@ -0,0 +1,42 @@
+'use strict';
+
+require('../common');
+const assert = require('assert');
+const fs = require('fs');
+
+const errUnknownBuiltinModuleRE = /^No such built-in module: /u;
+
+// For direct use of require expressions inside of CJS modules,
+// all kinds of specifiers should work without issue.
+{
+  assert.strictEqual(require('fs'), fs);
+  assert.strictEqual(require('node:fs'), fs);
+
+  assert.throws(
+    () => require('node:unknown'),
+    {
+      code: 'ERR_UNKNOWN_BUILTIN_MODULE',
+      message: errUnknownBuiltinModuleRE,
+    },
+  );
+
+  assert.throws(
+    () => require('node:internal/test/binding'),
+    {
+      code: 'ERR_UNKNOWN_BUILTIN_MODULE',
+      message: errUnknownBuiltinModuleRE,
+    },
+  );
+}
+
+// `node:`-prefixed `require(...)` calls bypass the require cache:
+{
+  const fakeModule = {};
+
+  require.cache.fs = { exports: fakeModule };
+
+  assert.strictEqual(require('fs'), fakeModule);
+  assert.strictEqual(require('node:fs'), fs);
+
+  delete require.cache.fs;
+}