From 9d918d99236ac3c2e43d86b9648b0b210ec63368 Mon Sep 17 00:00:00 2001
From: "hemanth.hm" <hemanth.hm@gmail.com>
Date: Fri, 8 Jul 2022 01:12:32 -0700
Subject: [PATCH] module: add isBuiltIn method
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PR-URL: https://github.com/nodejs/node/pull/43396
Fixes: https://github.com/nodejs/node/issues/42785
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>
Reviewed-By: Juan José Arboleda <soyjuanarbol@gmail.com>
---
 doc/api/module.md                      | 16 ++++++++++++++++
 lib/internal/modules/cjs/loader.js     | 11 +++++++++++
 test/parallel/test-module-isBuiltin.js | 16 ++++++++++++++++
 3 files changed, 43 insertions(+)
 create mode 100644 test/parallel/test-module-isBuiltin.js

diff --git a/doc/api/module.md b/doc/api/module.md
index 85ba9a79e2291d..04b5263155c76b 100644
--- a/doc/api/module.md
+++ b/doc/api/module.md
@@ -62,6 +62,22 @@ const require = createRequire(import.meta.url);
 const siblingModule = require('./sibling-module');
 ```
 
+### `module.isBuiltin(moduleName)`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+* `moduleName` {string} name of the module
+* Returns: {boolean} returns true if the module is builtin else returns false
+
+```mjs
+import { isBuiltin } from 'node:module';
+isBuiltin('node:fs'); // true
+isBuiltin('fs'); // true
+isBuiltin('wss'); // false
+```
+
 ### `module.syncBuiltinESMExports()`
 
 <!-- YAML
diff --git a/lib/internal/modules/cjs/loader.js b/lib/internal/modules/cjs/loader.js
index 2f55b09c149f75..711589894d5d19 100644
--- a/lib/internal/modules/cjs/loader.js
+++ b/lib/internal/modules/cjs/loader.js
@@ -33,6 +33,7 @@ const {
   ArrayPrototypeSplice,
   ArrayPrototypeUnshift,
   ArrayPrototypeUnshiftApply,
+  ArrayPrototypeFlatMap,
   Boolean,
   Error,
   JSONParse,
@@ -50,6 +51,7 @@ const {
   ReflectSet,
   RegExpPrototypeExec,
   SafeMap,
+  SafeSet,
   SafeWeakMap,
   String,
   StringPrototypeCharAt,
@@ -186,6 +188,11 @@ for (const { 0: id, 1: mod } of NativeModule.map) {
   }
 }
 
+const allBuiltins = new SafeSet(
+  ArrayPrototypeFlatMap(builtinModules, (bm) => [bm, `node:${bm}`])
+);
+NativeModule.getSchemeOnlyModuleNames().forEach((builtin) => allBuiltins.add(`node:${builtin}`));
+
 ObjectFreeze(builtinModules);
 Module.builtinModules = builtinModules;
 
@@ -1300,5 +1307,9 @@ Module.syncBuiltinESMExports = function syncBuiltinESMExports() {
   }
 };
 
+Module.isBuiltin = function isBuiltin(moduleName) {
+  return allBuiltins.has(moduleName);
+};
+
 // Backwards compatibility
 Module.Module = Module;
diff --git a/test/parallel/test-module-isBuiltin.js b/test/parallel/test-module-isBuiltin.js
new file mode 100644
index 00000000000000..a7815a8dfc1c18
--- /dev/null
+++ b/test/parallel/test-module-isBuiltin.js
@@ -0,0 +1,16 @@
+'use strict';
+require('../common');
+const assert = require('assert');
+const { isBuiltin } = require('module');
+
+// Includes modules in lib/ (even deprecated ones)
+assert(isBuiltin('http'));
+assert(isBuiltin('sys'));
+assert(isBuiltin('node:fs'));
+assert(isBuiltin('node:test'));
+
+// Does not include internal modules
+assert(!isBuiltin('internal/errors'));
+assert(!isBuiltin('test'));
+assert(!isBuiltin(''));
+assert(!isBuiltin(undefined));