Mirror linked task behaviour from other implementations: default to terminating facet on task end, and also terminate facet on task exception

chat.py

@@ -29,6 +29,8 @@ def main():
 
     @syndicate.relay.connect(args.address, sturdy.SturdyRef.decode(syndicate.parse(args.cap)))
     def on_connected(ds):
+        turn.on_stop(lambda: turn.stop(root_facet))
+
         me = 'user_' + str(random.randint(10, 1000))
 
         turn.publish(ds, Present(me))
@@ -48,4 +50,3 @@ def main():
             await f.loop.connect_read_pipe(lambda: asyncio.StreamReaderProtocol(reader), sys.stdin)
             while line := (await reader.readline()).decode('utf-8'):
                 turn.external(f, lambda: turn.send(ds, Says(me, line.strip())))
-            turn.external(f, lambda: turn.stop(root_facet))

syndicate/actor.py

@@ -251,15 +251,20 @@ class Facet:
                 task.cancel()
                 task = None
         async def guarded_task():
+            should_terminate_facet = True
             try:
-                await coro_fn(self)
+                if await coro_fn(self) is True:
+                    should_terminate_facet = False
             except asyncio.CancelledError:
                 pass
             except:
                 import traceback
                 traceback.print_exc()
             finally:
-                Turn.external(self, cancel_linked_task)
+                if should_terminate_facet:
+                    Turn.external(self, lambda: Turn.active.stop())
+                else:
+                    Turn.external(self, cancel_linked_task)
         task = self.loop.create_task(guarded_task())
         self.linked_tasks.append(task)