module: allow passing a directory to createRequireFromPath

Fixes: #23710

PR-URL: #23818
Reviewed-By: Guy Bedford <guybedford@gmail.com>
Reviewed-By: Myles Borins <myles.borins@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

doc/api/modules.md

@@ -916,7 +916,7 @@ added: v10.12.0
 
 ```js
 const { createRequireFromPath } = require('module');
-const requireUtil = createRequireFromPath('../src/utils');
+const requireUtil = createRequireFromPath('../src/utils/');
 
 // Require `../src/utils/some-tool`
 requireUtil('./some-tool');

lib/internal/modules/cjs/loader.js

@@ -825,9 +825,18 @@ Module.runMain = function() {
 };
 
 Module.createRequireFromPath = (filename) => {
-  const m = new Module(filename);
-  m.filename = filename;
-  m.paths = Module._nodeModulePaths(path.dirname(filename));
+  // Allow a directory to be passed as the filename
+  const trailingSlash =
+    filename.endsWith(path.sep) || path.sep !== '/' && filename.endsWith('\\');
+
+  const proxyPath = trailingSlash ?
+    path.join(filename, 'noop.js') :
+    filename;
+
+  const m = new Module(proxyPath);
+  m.filename = proxyPath;
+
+  m.paths = Module._nodeModulePaths(m.path);
   return makeRequireFunction(m);
 };
 

test/parallel/test-module-create-require-from-directory.js

@@ -0,0 +1,18 @@
+'use strict';
+
+require('../common');
+const assert = require('assert');
+const path = require('path');
+
+const { createRequireFromPath } = require('module');
+
+const fixPath = path.resolve(__dirname, '..', 'fixtures');
+const p = path.join(fixPath, path.sep);
+
+const req = createRequireFromPath(p);
+const reqFromNotDir = createRequireFromPath(fixPath);
+
+assert.strictEqual(req('./baz'), 'perhaps I work');
+assert.throws(() => {
+  reqFromNotDir('./baz');
+}, { code: 'MODULE_NOT_FOUND' });