fix: fall back for npx cache subprocess check (#3560)

Co-authored-by: Alexandre Teixeira <111787685+alteixeira20@users.noreply.github.com>

src/builtin_mcp.py

@@ -8,6 +8,7 @@ Each server runs as a stdio subprocess managed by McpManager.
 import logging
 import os
 import shutil
+import subprocess
 import sys
 import asyncio
 
@@ -208,6 +209,16 @@ async def _is_npx_package_cached(npx_path, package_spec, timeout_s=5):
             stdout=asyncio.subprocess.PIPE,
             stderr=asyncio.subprocess.PIPE,
         )
+    except NotImplementedError:
+        try:
+            result = subprocess.run(
+                [npx_path, "--no-install", package_spec, "--version"],
+                capture_output=True,
+                timeout=timeout_s,
+            )
+        except (subprocess.TimeoutExpired, OSError, ValueError):
+            return False
+        return result.returncode == 0 and bool(result.stdout.strip())
     except (OSError, ValueError):
         return False
     try:

tests/test_builtin_mcp_npx_cache.py

@@ -0,0 +1,90 @@
+import asyncio
+import importlib.util
+from pathlib import Path
+import subprocess
+import sys
+import types
+
+
+ROOT = Path(__file__).resolve().parent.parent
+
+
+def _load_builtin_mcp(monkeypatch):
+    core = types.ModuleType("core")
+    core.__path__ = []
+    platform_compat = types.ModuleType("core.platform_compat")
+    platform_compat.IS_WINDOWS = False
+    platform_compat.which_tool = lambda name: None
+    monkeypatch.setitem(sys.modules, "core", core)
+    monkeypatch.setitem(sys.modules, "core.platform_compat", platform_compat)
+
+    spec = importlib.util.spec_from_file_location(
+        "builtin_mcp_under_test",
+        ROOT / "src" / "builtin_mcp.py",
+    )
+    module = importlib.util.module_from_spec(spec)
+    assert spec.loader is not None
+    spec.loader.exec_module(module)
+    return module
+
+
+def test_npx_package_from_args_prefers_package_after_y_flag(monkeypatch):
+    builtin_mcp = _load_builtin_mcp(monkeypatch)
+
+    assert builtin_mcp._npx_package_from_args(
+        ["-y", "@playwright/mcp@latest", "--headless"]
+    ) == "@playwright/mcp@latest"
+
+
+def test_npx_cache_check_falls_back_when_async_subprocess_is_unsupported(monkeypatch):
+    builtin_mcp = _load_builtin_mcp(monkeypatch)
+
+    async def unsupported_exec(*args, **kwargs):
+        raise NotImplementedError("subprocess transport unavailable")
+
+    captured = {}
+
+    def fake_run(args, **kwargs):
+        captured["args"] = args
+        captured["kwargs"] = kwargs
+        return subprocess.CompletedProcess(args, 0, stdout=b"1.2.3\n", stderr=b"")
+
+    monkeypatch.setattr(builtin_mcp.asyncio, "create_subprocess_exec", unsupported_exec)
+    monkeypatch.setattr(builtin_mcp.subprocess, "run", fake_run)
+
+    assert asyncio.run(
+        builtin_mcp._is_npx_package_cached(
+            "npx.cmd",
+            "@playwright/mcp@latest",
+            timeout_s=2,
+        )
+    ) is True
+    assert captured["args"] == [
+        "npx.cmd",
+        "--no-install",
+        "@playwright/mcp@latest",
+        "--version",
+    ]
+    assert captured["kwargs"]["capture_output"] is True
+    assert captured["kwargs"]["timeout"] == 2
+
+
+def test_npx_cache_check_fallback_treats_timeout_as_cache_miss(monkeypatch):
+    builtin_mcp = _load_builtin_mcp(monkeypatch)
+
+    async def unsupported_exec(*args, **kwargs):
+        raise NotImplementedError("subprocess transport unavailable")
+
+    def fake_run(args, **kwargs):
+        raise subprocess.TimeoutExpired(args, kwargs["timeout"])
+
+    monkeypatch.setattr(builtin_mcp.asyncio, "create_subprocess_exec", unsupported_exec)
+    monkeypatch.setattr(builtin_mcp.subprocess, "run", fake_run)
+
+    assert asyncio.run(
+        builtin_mcp._is_npx_package_cached(
+            "npx.cmd",
+            "@playwright/mcp@latest",
+            timeout_s=2,
+        )
+    ) is False