Address PR comments

Author: saqadri

src/mcp/client/stdio.py src/mcp/client/stdio/__init__.pysrc/mcp/client/stdio.py renamed to src/mcp/client/stdio/__init__.py

@@ -1,6 +1,4 @@
 import os
-import shutil
-import subprocess
 import sys
 from contextlib import asynccontextmanager
 from pathlib import Path
@@ -14,6 +12,8 @@
 
 import mcp.types as types
 
+from .win32 import create_windows_process, get_windows_executable_command
+
 # Environment variables to inherit by default
 DEFAULT_INHERITED_ENV_VARS = (
     [
@@ -115,7 +115,7 @@ async def stdio_client(server: StdioServerParameters, errlog: TextIO = sys.stder
             else get_default_environment()
         ),
         errlog=errlog,
-        cwd=server.cwd
+        cwd=server.cwd,
     )
 
     async def stdout_reader():
@@ -172,9 +172,9 @@ async def stdin_writer():
             try:
                 process.terminate()
                 if sys.platform == "win32":
-                    # On Windows, terminating a process with process.terminate() doesn't 
-                    # always guarantee immediate process termination. 
-                    # So we give it 2s to exit, or we call process.kill() 
+                    # On Windows, terminating a process with process.terminate() doesn't
+                    # always guarantee immediate process termination.
+                    # So we give it 2s to exit, or we call process.kill()
                     # which sends a SIGKILL equivalent signal.
                     try:
                         with anyio.fail_after(2.0):
@@ -196,28 +196,9 @@ def _get_executable_command(command: str) -> str:
     Returns:
         str: Platform-appropriate command
     """
-
-    try:
-        if sys.platform != "win32":
-            return command
-        else:
-            # For Windows, we need more sophisticated path resolution
-            # First check if command exists in PATH as-is
-            if command_path:= shutil.which(command):
-                return command_path
-
-            # Check for Windows-specific extensions
-            for ext in [".cmd", ".bat", ".exe", ".ps1"]:
-                ext_version = f"{command}{ext}"
-                if ext_path:= shutil.which(ext_version):
-                    return ext_path
-
-            # For regular commands or if we couldn't find special versions
-            return command
-    except Exception:
-        # If anything goes wrong, just return the original command
-        # shutil.which() could raise exceptions if there are permission 
-        # issues accessing directories in PATH
+    if sys.platform == "win32":
+        return get_windows_executable_command(command)
+    else:
         return command
 
 
@@ -232,28 +213,8 @@ async def _create_platform_compatible_process(
     Creates a subprocess in a platform-compatible way.
     Returns a process handle.
     """
-
-    process = None
-
     if sys.platform == "win32":
-        try:
-            process = await anyio.open_process(
-                [command, *args],
-                env=env,
-                # Ensure we don't create console windows for each process
-                creationflags=subprocess.CREATE_NO_WINDOW  # type: ignore
-                if hasattr(subprocess, "CREATE_NO_WINDOW")
-                else 0,
-                stderr=errlog,
-                cwd=cwd,
-            )
-
-            return process
-        except Exception:
-            # Don't raise, let's try to create the process without creation flags   
-            process = await anyio.open_process(
-                [command, *args], env=env, stderr=errlog, cwd=cwd
-            )
+        process = await create_windows_process(command, args, env, errlog, cwd)
     else:
         process = await anyio.open_process(
             [command, *args], env=env, stderr=errlog, cwd=cwd

src/mcp/client/stdio/win32.py

@@ -0,0 +1,87 @@
+"""
+Windows-specific functionality for stdio client operations.
+"""
+
+import shutil
+import subprocess
+import sys
+from pathlib import Path
+from typing import TextIO
+
+import anyio
+
+
+def get_windows_executable_command(command: str) -> str:
+    """
+    Get the correct executable command normalized for Windows.
+
+    On Windows, commands might exist with specific extensions (.exe, .cmd, etc.)
+    that need to be located for proper execution.
+
+    Args:
+        command: Base command (e.g., 'uvx', 'npx')
+
+    Returns:
+        str: Windows-appropriate command path
+    """
+    try:
+        # First check if command exists in PATH as-is
+        if command_path := shutil.which(command):
+            return command_path
+
+        # Check for Windows-specific extensions
+        for ext in [".cmd", ".bat", ".exe", ".ps1"]:
+            ext_version = f"{command}{ext}"
+            if ext_path := shutil.which(ext_version):
+                return ext_path
+
+        # For regular commands or if we couldn't find special versions
+        return command
+    except OSError:
+        # Handle file system errors during path resolution
+        # (permissions, broken symlinks, etc.)
+        return command
+
+
+async def create_windows_process(
+    command: str,
+    args: list[str],
+    env: dict[str, str] | None = None,
+    errlog: TextIO = sys.stderr,
+    cwd: Path | str | None = None,
+):
+    """
+    Creates a subprocess in a Windows-compatible way.
+
+    Windows processes need special handling for console windows and
+    process creation flags.
+
+    Args:
+        command: The command to execute
+        args: Command line arguments
+        env: Environment variables
+        errlog: Where to send stderr output
+        cwd: Working directory for the process
+
+    Returns:
+        A process handle
+    """
+    try:
+        # Try with Windows-specific flags to hide console window
+        process = await anyio.open_process(
+            [command, *args],
+            env=env,
+            # Ensure we don't create console windows for each process
+            creationflags=subprocess.CREATE_NO_WINDOW  # type: ignore
+            if hasattr(subprocess, "CREATE_NO_WINDOW")
+            else 0,
+            stderr=errlog,
+            cwd=cwd,
+        )
+        return process
+    except Exception:
+        # Don't raise, let's try to create the process without creation flags
+        process = await anyio.open_process(
+            [command, *args], env=env, stderr=errlog, cwd=cwd
+        )
+        return process