test: satisfy stdio pyright checks

Author: Henry Lee

src/mcp/server/stdio.py

@@ -19,8 +19,10 @@ async def run_server():
 
 import os
 import sys
+from collections.abc import Callable
 from contextlib import asynccontextmanager
 from io import TextIOWrapper, UnsupportedOperation
+from typing import BinaryIO, Literal, Protocol
 
 import anyio
 import anyio.lowlevel
@@ -30,7 +32,19 @@ async def run_server():
 from mcp.shared.message import SessionMessage
 
 
-def _wrap_standard_stream(stream, mode: str, *, errors: str | None = None) -> tuple[anyio.AsyncFile[str], bool]:
+class _TextStreamWithBuffer(Protocol):
+    @property
+    def buffer(self) -> BinaryIO: ...
+
+    fileno: Callable[[], int]
+
+
+def _wrap_standard_stream(
+    stream: _TextStreamWithBuffer,
+    mode: Literal["rb", "wb"],
+    *,
+    errors: str | None = None,
+) -> tuple[anyio.AsyncFile[str], bool]:
     """Wrap a standard stream without taking ownership of the original handle."""
     try:
         fd = os.dup(stream.fileno())

tests/server/test_stdio.py

@@ -2,6 +2,7 @@
 import io
 import sys
 from io import TextIOWrapper
+from pathlib import Path
 
 import anyio
 import pytest
@@ -96,7 +97,7 @@ async def test_stdio_server_invalid_utf8(monkeypatch: pytest.MonkeyPatch):
 
 
 @pytest.mark.anyio
-async def test_stdio_server_does_not_close_standard_streams(monkeypatch: pytest.MonkeyPatch, tmp_path):
+async def test_stdio_server_does_not_close_standard_streams(monkeypatch: pytest.MonkeyPatch, tmp_path: Path):
     """Default stdio wrapping must not close the process stdin/stdout handles."""
     message = JSONRPCRequest(jsonrpc="2.0", id=1, method="ping")
     stdin_path = tmp_path / "stdin.jsonl"