Read marionette socket

test/common/bidi.py

@@ -375,31 +375,42 @@ async def start_bidi_session(self) -> None:
         for _ in range(1, 30):
             try:
                 # we must keep this socket open throughout the lifetime of that session
-                reader, self.writer_marionette = await asyncio.open_connection("127.0.0.1", marionette_port)
+                self.reader_marionette, self.writer_marionette = await asyncio.open_connection("127.0.0.1", marionette_port)
                 break
             except ConnectionRefusedError as e:
                 log_proto.debug("waiting for firefox marionette: %s", e)
                 await asyncio.sleep(1)
         else:
             raise WebdriverError("could not connect to firefox marionette")
 
-        reply = await reader.read(1024)
+        reply = await self.reader_marionette.read(1024)
         if b'"marionetteProtocol":3' not in reply:
             raise WebdriverError(f"unexpected marionette reply: {reply.decode()}")
         cmd = '[0,1,"WebDriver:NewSession",{"webSocketUrl":true,"acceptInsecureCerts":true}]'
         self.writer_marionette.write(f"{len(cmd)}:{cmd}".encode())
         await self.writer_marionette.drain()
-        reply = await reader.read(1024)
+        reply = await self.reader_marionette.read(1024)
         # cut off length prefix
         reply = json.loads(reply[reply.index(b":") + 1:].decode())
         if not isinstance(reply, list) or len(reply) != 4 or not isinstance(reply[3], dict):
             raise WebdriverError(f"unexpected marionette session request reply: {reply!r}")
         log_proto.debug("marionette session request reply: %s", reply)
 
+        # continue to read from Marionette, in case there are any messages; we must drain the pipe
+        self.marionette_logger: asyncio.Task = asyncio.create_task(self.log_marionette(), name="marionette_logger")
+
         url = reply[3]["capabilities"]["webSocketUrl"]
         self.bidi_session = BidiSession(session_url=url, ws_url=url, process=driver)
         log_proto.debug("Established firefox session %r", self.bidi_session)
 
+    async def log_marionette(self) -> None:
+        # we don't expect messages here, so log them as warnings
+        while True:
+            msg = await self.reader_marionette.read()
+            log_proto.warning("marionette: %s", msg)
+
     async def close_bidi_session(self) -> None:
+        self.marionette_logger.cancel()
+        del self.marionette_logger
         self.writer_marionette.close()
         await self.writer_marionette.wait_closed()