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

Fixes: #36098 Co-authored-by: Antoine du Hamel <duhamelantoine1995@gmail.com> Co-authored-by: Guy Bedford <guybedford@gmail.com> Co-authored-by: Darshan Sen <raisinten@gmail.com> PR-URL: #37246 Reviewed-By: Bradley Farias <bradley.meck@gmail.com> Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com> Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com> Reviewed-By: Darshan Sen <raisinten@gmail.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
nodejs · Mar 19, 2021 · 069b5df4f66f87a9ccef008f3982c916e628b9ef · 069b5df
1 parent b079960
commit 069b5df4f66f87a9ccef008f3982c916e628b9ef
diff --git a/doc/api/esm.md b/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

diff --git a/doc/api/modules.md b/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.
@@ -291,6 +297,11 @@ 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.
 
+Core modules can also be identified using the `node:` prefix, in which case
+it bypasses the `require` cache. For instance, `require('node:http')` will
+always return the built in HTTP module, even if there is `require.cache` entry
+by that name.
+
 ## Cycles
 
 <!--type=misc-->
@@ -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

diff --git a/lib/internal/modules/cjs/helpers.js b/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;
   }

diff --git a/lib/internal/modules/cjs/loader.js b/lib/internal/modules/cjs/loader.js
@@ -110,7 +110,8 @@ 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');
@@ -770,6 +771,17 @@ 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) {
@@ -841,7 +853,8 @@ 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;
   }
 

diff --git a/lib/internal/modules/esm/translators.js b/lib/internal/modules/esm/translators.js
@@ -282,7 +282,7 @@ 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);
+  const module = loadNativeModule(id, url);
   if (!StringPrototypeStartsWith(url, 'node:') || !module) {
     throw new ERR_UNKNOWN_BUILTIN_MODULE(url);
   }

diff --git a/test/es-module/test-esm-dynamic-import.js b/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'),

diff --git a/test/parallel/test-require-node-prefix.js b/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;
+}