module: handle relative paths in resolve paths

This commit adds support for relative paths in
require.resolve()'s paths option.

PR-URL: https://github.com/nodejs/node/pull/27598
Fixes: https://github.com/nodejs/node/issues/27583
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>

lib/internal/modules/cjs/loader.js

@@ -575,6 +575,12 @@ Module._resolveFilename = function(request, parent, isMain, options) {
 
   if (typeof options === 'object' && options !== null &&
       Array.isArray(options.paths)) {
+    const isRelative = request.startsWith('./') || request.startsWith('../') ||
+        (isWindows && request.startsWith('.\\') || request.startsWith('..\\'));
+
+    if (isRelative) {
+      paths = options.paths;
+    } else {
       const fakeParent = new Module('', null);
 
       paths = [];
@@ -589,6 +595,7 @@ Module._resolveFilename = function(request, parent, isMain, options) {
             paths.push(lookupPaths[j]);
         }
       }
+    }
   } else {
     paths = Module._resolveLookupPaths(request, parent);
   }

test/fixtures/require-resolve.js

@@ -1,5 +1,5 @@
 'use strict';
-require('../common');
+const common = require('../common');
 const assert = require('assert');
 const path = require('path');
 const nodeModules = path.join(__dirname, 'node_modules');
@@ -54,3 +54,33 @@ assert.throws(() => {
     path.join(nodeModules, 'bar.js')
   );
 }
+
+// Verify that relative request paths work properly.
+{
+  const searchIn = './' + path.relative(process.cwd(), nestedIndex);
+
+  // Search in relative paths.
+  assert.strictEqual(
+    require.resolve('./three.js', { paths: [searchIn] }),
+    path.join(nestedIndex, 'three.js')
+  );
+
+  // Search in absolute paths.
+  assert.strictEqual(
+    require.resolve('./three.js', { paths: [nestedIndex] }),
+    path.join(nestedIndex, 'three.js')
+  );
+
+  // Repeat the same tests with Windows slashes in the request path.
+  if (common.isWindows) {
+    assert.strictEqual(
+      require.resolve('.\\three.js', { paths: [searchIn] }),
+      path.join(nestedIndex, 'three.js')
+    );
+
+    assert.strictEqual(
+      require.resolve('.\\three.js', { paths: [nestedIndex] }),
+      path.join(nestedIndex, 'three.js')
+    );
+  }
+}