Use the highest available pickle protocol

lahja/asyncio/endpoint.py

@@ -89,7 +89,7 @@ async def connect_to(cls, path: Path) -> ConnectionAPI:
         return cls(reader, writer)
 
     async def send_message(self, message: Msg) -> None:
-        pickled = pickle.dumps(message)
+        pickled = pickle.dumps(message, protocol=pickle.HIGHEST_PROTOCOL)
         size = len(pickled)
 
         try:

lahja/base.py

@@ -776,7 +776,10 @@ def _compress_event(self, event: BaseEvent) -> Union[BaseEvent, bytes]:
         if self.has_snappy_support:
             import snappy
 
-            return cast(bytes, snappy.compress(pickle.dumps(event)))
+            return cast(
+                bytes,
+                snappy.compress(pickle.dumps(event, protocol=pickle.HIGHEST_PROTOCOL))
+            )
         else:
             return event
 

lahja/trio/endpoint.py

@@ -90,7 +90,7 @@ async def connect_to(cls, path: pathlib.Path) -> "TrioConnection":
         return cls(socket)
 
     async def send_message(self, message: Msg) -> None:
-        msg_data = pickle.dumps(message)
+        msg_data = pickle.dumps(message, protocol=pickle.HIGHEST_PROTOCOL)
         size = len(msg_data)
         try:
             async with self._write_lock:

newsfragments/156.feature.rst

@@ -0,0 +1 @@
+Ensure ``stream()`` does not suppress ``CancelledError``

newsfragments/160.feature.rst

@@ -0,0 +1,3 @@
+Use the highest available `pickle` protocol. This yields a notable performance
+improvement on Python < 3.8 which are still using version 3 of the protocol by
+default.

tests/core/asyncio/test_basics.py

@@ -258,4 +258,4 @@ def test_pickle_fails():
     alice = AsyncioEndpoint("pickle-test")
 
     with pytest.raises(Exception):
-        pickle.dumps(alice)
+        pickle.dumps(alice, protocol=pickle.HIGHEST_PROTOCOL))