From e8e21fb6f8172e82dd2b846dfa53826ea90abf27 Mon Sep 17 00:00:00 2001
From: Dario Piotrowicz <dario.piotrowicz@gmail.com>
Date: Sat, 25 Jan 2025 23:32:13 +0000
Subject: [PATCH] module: fix bad `require.resolve` with option paths for `.`
 and `..`

this change fixes `require.resolve` used with the `paths` option
not considering `.` and `..` as relative

Fixes: https://github.com/nodejs/node/issues/47000
PR-URL: https://github.com/nodejs/node/pull/56735
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jordan Harband <ljharb@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
---
 lib/internal/modules/cjs/loader.js            | 34 +++++++--------
 .../relative/subdir/relative-subdir.js        |  1 +
 ...est-require-resolve-opts-paths-relative.js | 43 +++++++++++++++++++
 3 files changed, 61 insertions(+), 17 deletions(-)
 create mode 100644 test/fixtures/module-require/relative/subdir/relative-subdir.js
 create mode 100644 test/parallel/test-require-resolve-opts-paths-relative.js

diff --git a/lib/internal/modules/cjs/loader.js b/lib/internal/modules/cjs/loader.js
index 236b2484049c43..e21bcb798c4d53 100644
--- a/lib/internal/modules/cjs/loader.js
+++ b/lib/internal/modules/cjs/loader.js
@@ -713,18 +713,8 @@ Module._findPath = function(request, paths, isMain) {
       )
     ));
 
-  const isRelative = StringPrototypeCharCodeAt(request, 0) === CHAR_DOT &&
-    (
-      request.length === 1 ||
-      StringPrototypeCharCodeAt(request, 1) === CHAR_FORWARD_SLASH ||
-      (isWindows && StringPrototypeCharCodeAt(request, 1) === CHAR_BACKWARD_SLASH) ||
-      (StringPrototypeCharCodeAt(request, 1) === CHAR_DOT && ((
-        request.length === 2 ||
-        StringPrototypeCharCodeAt(request, 2) === CHAR_FORWARD_SLASH) ||
-        (isWindows && StringPrototypeCharCodeAt(request, 2) === CHAR_BACKWARD_SLASH)))
-    );
   let insidePath = true;
-  if (isRelative) {
+  if (isRelative(request)) {
     const normalizedRequest = path.normalize(request);
     if (StringPrototypeStartsWith(normalizedRequest, '..')) {
       insidePath = false;
@@ -1164,12 +1154,7 @@ Module._resolveFilename = function(request, parent, isMain, options) {
 
   if (typeof options === 'object' && options !== null) {
     if (ArrayIsArray(options.paths)) {
-      const isRelative = StringPrototypeStartsWith(request, './') ||
-          StringPrototypeStartsWith(request, '../') ||
-          ((isWindows && StringPrototypeStartsWith(request, '.\\')) ||
-          StringPrototypeStartsWith(request, '..\\'));
-
-      if (isRelative) {
+      if (isRelative(request)) {
         paths = options.paths;
       } else {
         const fakeParent = new Module('', null);
@@ -1774,6 +1759,21 @@ function createRequire(filename) {
   return createRequireFromPath(filepath);
 }
 
+/**
+ * Checks if a path is relative
+ * @param {string} path the target path
+ * @returns {boolean} true if the path is relative, false otherwise
+ */
+function isRelative(path) {
+  if (StringPrototypeCharCodeAt(path, 0) !== CHAR_DOT) { return false; }
+
+  return path.length === 1 || path === '..' ||
+  StringPrototypeStartsWith(path, './') ||
+  StringPrototypeStartsWith(path, '../') ||
+  ((isWindows && StringPrototypeStartsWith(path, '.\\')) ||
+  StringPrototypeStartsWith(path, '..\\'));
+}
+
 Module.createRequire = createRequire;
 
 /**
diff --git a/test/fixtures/module-require/relative/subdir/relative-subdir.js b/test/fixtures/module-require/relative/subdir/relative-subdir.js
new file mode 100644
index 00000000000000..34eb71b3c6ca39
--- /dev/null
+++ b/test/fixtures/module-require/relative/subdir/relative-subdir.js
@@ -0,0 +1 @@
+exports.value = 'relative subdir';
diff --git a/test/parallel/test-require-resolve-opts-paths-relative.js b/test/parallel/test-require-resolve-opts-paths-relative.js
new file mode 100644
index 00000000000000..522a1fdbce82a4
--- /dev/null
+++ b/test/parallel/test-require-resolve-opts-paths-relative.js
@@ -0,0 +1,43 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const fixtures = require('../common/fixtures');
+
+if (!common.isMainThread)
+  common.skip('process.chdir is not available in Workers');
+
+const subdir = fixtures.path('module-require', 'relative', 'subdir');
+
+process.chdir(subdir);
+
+// Parent directory paths (`..`) work as intended
+{
+  assert(require.resolve('.', { paths: ['../'] }).endsWith('index.js'));
+  assert(require.resolve('./index.js', { paths: ['../'] }).endsWith('index.js'));
+
+  // paths: [".."] should resolve like paths: ["../"]
+  assert(require.resolve('.', { paths: ['..'] }).endsWith('index.js'));
+  assert(require.resolve('./index.js', { paths: ['..'] }).endsWith('index.js'));
+}
+
+process.chdir('..');
+
+// Current directory paths (`.`) work as intended
+{
+  assert(require.resolve('.', { paths: ['.'] }).endsWith('index.js'));
+  assert(require.resolve('./index.js', { paths: ['./'] }).endsWith('index.js'));
+
+  // paths: ["."] should resolve like paths: ["../"]
+  assert(require.resolve('.', { paths: ['.'] }).endsWith('index.js'));
+  assert(require.resolve('./index.js', { paths: ['.'] }).endsWith('index.js'));
+}
+
+// Sub directory paths work as intended
+{
+  // assert.deepStrictEqual(fs.readdirSync('./subdir'), [5]);
+  assert(require.resolve('./relative-subdir.js', { paths: ['./subdir'] }).endsWith('relative-subdir.js'));
+
+  // paths: ["subdir"] should resolve like paths: ["./subdir"]
+  assert(require.resolve('./relative-subdir.js', { paths: ['subdir'] }).endsWith('relative-subdir.js'));
+}