Close all portal created async gens on shutdown

tractor/_portal.py

@@ -65,6 +65,7 @@ class Portal:
         self._expect_result: Optional[
             Tuple[str, Any, str, Dict[str, Any]]
         ] = None
+        self._agens: Set(AsyncGenerator) = set()
 
     async def aclose(self) -> None:
         log.debug(f"Closing {self}")
@@ -142,14 +143,16 @@ class Portal:
                 except GeneratorExit:
                     # for now this msg cancels an ongoing remote task
                     await self.channel.send({'cancel': True, 'cid': cid})
-                    log.debug(
+                    log.warn(
                         f"Cancelling async gen call {cid} to "
                         f"{self.channel.uid}")
                     raise
 
             # TODO: use AsyncExitStack to aclose() all agens
             # on teardown
-            return yield_from_q()
+            agen = yield_from_q()
+            self._agens.add(agen)
+            return agen
 
         elif resptype == 'return':
             msg = await q.get()
@@ -269,7 +272,12 @@ async def open_portal(
 
         nursery.start_soon(actor._process_messages, channel)
         portal = Portal(channel)
+        try:
             yield portal
+        finally:
+            # tear down all async generators
+            for agen in portal._agens:
+                await agen.aclose()
 
             # cancel remote channel-msg loop
             if channel.connected():