From e564b4a8080cff48fa0c28f20272c05085ee6130 Mon Sep 17 00:00:00 2001
From: Simon Sawicki <contact@grub4k.dev>
Date: Mon, 24 Nov 2025 01:56:43 +0100
Subject: [PATCH] Respect `PATHEXT` when locating JS runtime on Windows
 (#15117)

Fixes #15043

Authored by: Grub4K
---
 yt_dlp/utils/_jsruntime.py | 54 +++++++++++++++++++++++++++++++++-----
 yt_dlp/utils/_utils.py     | 20 +++++++++-----
 2 files changed, 60 insertions(+), 14 deletions(-)

diff --git a/yt_dlp/utils/_jsruntime.py b/yt_dlp/utils/_jsruntime.py
index bd8fd1f880..94db52bf19 100644
--- a/yt_dlp/utils/_jsruntime.py
+++ b/yt_dlp/utils/_jsruntime.py
@@ -1,21 +1,61 @@
 from __future__ import annotations
+
 import abc
 import dataclasses
 import functools
 import os.path
+import sys
 
 from ._utils import _get_exe_version_output, detect_exe_version, int_or_none
 
 
-# NOT public API
-def runtime_version_tuple(v):
+def _runtime_version_tuple(v):
     # NB: will return (0,) if `v` is an invalid version string
     return tuple(int_or_none(x, default=0) for x in v.split('.'))
 
 
+_FALLBACK_PATHEXT = ('.COM', '.EXE', '.BAT', '.CMD')
+
+
+def _find_exe(basename: str) -> str:
+    if os.name != 'nt':
+        return basename
+
+    paths: list[str] = []
+
+    # binary dir
+    if getattr(sys, 'frozen', False):
+        paths.append(os.path.dirname(sys.executable))
+    # cwd
+    paths.append(os.getcwd())
+    # PATH items
+    if path := os.environ.get('PATH'):
+        paths.extend(filter(None, path.split(os.path.pathsep)))
+
+    pathext = os.environ.get('PATHEXT')
+    if pathext is None:
+        exts = _FALLBACK_PATHEXT
+    else:
+        exts = tuple(ext for ext in pathext.split(os.pathsep) if ext)
+
+    visited = []
+    for path in map(os.path.realpath, paths):
+        normed = os.path.normcase(path)
+        if normed in visited:
+            continue
+        visited.append(normed)
+
+        for ext in exts:
+            binary = os.path.join(path, f'{basename}{ext}')
+            if os.access(binary, os.F_OK | os.X_OK) and not os.path.isdir(binary):
+                return binary
+
+    return basename
+
+
 def _determine_runtime_path(path, basename):
     if not path:
-        return basename
+        return _find_exe(basename)
     if os.path.isdir(path):
         return os.path.join(path, basename)
     return path
@@ -52,7 +92,7 @@ class DenoJsRuntime(JsRuntime):
         if not out:
             return None
         version = detect_exe_version(out, r'^deno (\S+)', 'unknown')
-        vt = runtime_version_tuple(version)
+        vt = _runtime_version_tuple(version)
         return JsRuntimeInfo(
             name='deno', path=path, version=version, version_tuple=vt,
             supported=vt >= self.MIN_SUPPORTED_VERSION)
@@ -67,7 +107,7 @@ class BunJsRuntime(JsRuntime):
         if not out:
             return None
         version = detect_exe_version(out, r'^(\S+)', 'unknown')
-        vt = runtime_version_tuple(version)
+        vt = _runtime_version_tuple(version)
         return JsRuntimeInfo(
             name='bun', path=path, version=version, version_tuple=vt,
             supported=vt >= self.MIN_SUPPORTED_VERSION)
@@ -82,7 +122,7 @@ class NodeJsRuntime(JsRuntime):
         if not out:
             return None
         version = detect_exe_version(out, r'^v(\S+)', 'unknown')
-        vt = runtime_version_tuple(version)
+        vt = _runtime_version_tuple(version)
         return JsRuntimeInfo(
             name='node', path=path, version=version, version_tuple=vt,
             supported=vt >= self.MIN_SUPPORTED_VERSION)
@@ -100,7 +140,7 @@ class QuickJsRuntime(JsRuntime):
         is_ng = 'QuickJS-ng' in out
 
         version = detect_exe_version(out, r'^QuickJS(?:-ng)?\s+version\s+(\S+)', 'unknown')
-        vt = runtime_version_tuple(version.replace('-', '.'))
+        vt = _runtime_version_tuple(version.replace('-', '.'))
         if is_ng:
             return JsRuntimeInfo(
                 name='quickjs-ng', path=path, version=version, version_tuple=vt,
diff --git a/yt_dlp/utils/_utils.py b/yt_dlp/utils/_utils.py
index c6ae21f6c7..65cd2373ce 100644
--- a/yt_dlp/utils/_utils.py
+++ b/yt_dlp/utils/_utils.py
@@ -876,13 +876,19 @@ class Popen(subprocess.Popen):
             kwargs.setdefault('encoding', 'utf-8')
             kwargs.setdefault('errors', 'replace')
 
-        if shell and os.name == 'nt' and kwargs.get('executable') is None:
-            if not isinstance(args, str):
-                args = shell_quote(args, shell=True)
-            shell = False
-            # Set variable for `cmd.exe` newline escaping (see `utils.shell_quote`)
-            env['='] = '"^\n\n"'
-            args = f'{self.__comspec()} /Q /S /D /V:OFF /E:ON /C "{args}"'
+        if os.name == 'nt' and kwargs.get('executable') is None:
+            # Must apply shell escaping if we are trying to run a batch file
+            # These conditions should be very specific to limit impact
+            if not shell and isinstance(args, list) and args and args[0].lower().endswith(('.bat', '.cmd')):
+                shell = True
+
+            if shell:
+                if not isinstance(args, str):
+                    args = shell_quote(args, shell=True)
+                shell = False
+                # Set variable for `cmd.exe` newline escaping (see `utils.shell_quote`)
+                env['='] = '"^\n\n"'
+                args = f'{self.__comspec()} /Q /S /D /V:OFF /E:ON /C "{args}"'
 
         super().__init__(args, *remaining, env=env, shell=shell, **kwargs, startupinfo=self._startupinfo)