Convert bytearray to bytes in StreamProtocol.receive() (agronholm#777)

Fixes agronholm#776.

docs/versionhistory.rst

@@ -20,6 +20,9 @@ This library adheres to `Semantic Versioning 2.0 <http://semver.org/>`_.
   (`#696 <https://github.com/agronholm/anyio/issues/696>`_)
 - Fixed ``TaskInfo.has_pending_cancellation()`` on asyncio not respecting shielded
   scopes (`#771 <https://github.com/agronholm/anyio/issues/771>`_; PR by @gschaffner)
+- Fixed ``SocketStream.receive()`` returning ``bytearray`` instead of ``bytes`` when
+  using asyncio with ``ProactorEventLoop`` (Windows)
+  (`#776 <https://github.com/agronholm/anyio/issues/776>`_)
 - Fixed quitting the debugger in a pytest test session while in an active task group
   failing the test instead of exiting the test session (because the exit exception
   arrives in an exception group)

src/anyio/_backends/_asyncio.py

@@ -1064,7 +1064,8 @@ def connection_lost(self, exc: Exception | None) -> None:
         self.write_event.set()
 
     def data_received(self, data: bytes) -> None:
-        self.read_queue.append(data)
+        # ProactorEventloop sometimes sends bytearray instead of bytes
+        self.read_queue.append(bytes(data))
         self.read_event.set()
 
     def eof_received(self) -> bool | None:

tests/test_sockets.py

@@ -202,7 +202,9 @@ def serve() -> None:
             thread.start()
             response = b""
             while len(response) < len(buffer):
-                response += await stream.receive()
+                chunk = await stream.receive()
+                assert isinstance(chunk, bytes)
+                response += chunk
 
         thread.join()
         assert response == buffer