Tweak broadcast fanout test to never inf loop

Since a bug in the new `MsgStream.aclose()` impl's drain block logic was
triggering an actual inf loop (by not ever canceller the streamer child
actor), make sure we put a loop limit on the `inf_streamer`()` XD

Also add a bit more deats to the test `print()`s in each actor and toss
in `debug_mode` fixture support.

tests/test_advanced_streaming.py

@@ -298,52 +298,77 @@ async def inf_streamer(
 
     async with (
         ctx.open_stream() as stream,
-        trio.open_nursery() as n,
+        trio.open_nursery() as tn,
     ):
-        async def bail_on_sentinel():
+        async def close_stream_on_sentinel():
             async for msg in stream:
                 if msg == 'done':
+                    print(
+                        'streamer RXed "done" sentinel msg!\n'
+                        'CLOSING `MsgStream`!'
+                    )
                     await stream.aclose()
                 else:
                     print(f'streamer received {msg}')
+            else:
+                print('streamer exited recv loop')
 
         # start termination detector
-        n.start_soon(bail_on_sentinel)
+        tn.start_soon(close_stream_on_sentinel)
 
-        for val in itertools.count():
+        cap: int = 10000  # so that we don't spin forever when bug..
+        for val in range(cap):
             try:
+                print(f'streamer sending {val}')
                 await stream.send(val)
-            except trio.ClosedResourceError:
+                if val > cap:
+                    raise RuntimeError(
+                        'Streamer never cancelled by setinel?'
+                    )
+                await trio.sleep(0.001)
+
             # close out the stream gracefully
+            except trio.ClosedResourceError:
+                print('msgstream closed on streamer side!')
+                assert stream.closed
                 break
+        else:
+            raise RuntimeError(
+                'Streamer not cancelled before finished sending?'
+            )
 
-    print('terminating streamer')
+    print('streamer exited .open_streamer() block')
 
 
-def test_local_task_fanout_from_stream():
+def test_local_task_fanout_from_stream(
+    debug_mode: bool,
+):
     '''
     Single stream with multiple local consumer tasks using the
     ``MsgStream.subscribe()` api.
 
-    Ensure all tasks receive all values after stream completes sending.
+    Ensure all tasks receive all values after stream completes
+    sending.
 
     '''
-    consumers = 22
+    consumers: int = 22
 
     async def main():
 
         counts = Counter()
 
-        async with tractor.open_nursery() as tn:
+        async with tractor.open_nursery(
-            p = await tn.start_actor(
+            debug_mode=debug_mode,
+        ) as tn:
+            p: tractor.Portal = await tn.start_actor(
                 'inf_streamer',
                 enable_modules=[__name__],
             )
+            # with trio.fail_after(3):
             async with (
                 p.open_context(inf_streamer) as (ctx, _),
                 ctx.open_stream() as stream,
             ):
-
                 async def pull_and_count(name: str):
                     # name = trio.lowlevel.current_task().name
                     async with stream.subscribe() as recver:
@@ -352,7 +377,7 @@ def test_local_task_fanout_from_stream():
                             tractor.trionics.BroadcastReceiver
                         )
                         async for val in recver:
-                            # print(f'{name}: {val}')
+                            print(f'bx {name} rx: {val}')
                             counts[name] += 1
 
                         print(f'{name} bcaster ended')
@@ -362,10 +387,14 @@ def test_local_task_fanout_from_stream():
                 with trio.fail_after(3):
                     async with trio.open_nursery() as nurse:
                         for i in range(consumers):
-                            nurse.start_soon(pull_and_count, i)
+                            nurse.start_soon(
+                                pull_and_count,
+                                i,
+                            )
 
+                        # delay to let bcast consumers pull msgs
                         await trio.sleep(0.5)
-                        print('\nterminating')
+                        print('terminating nursery of bcast rxer consumers!')
                         await stream.send('done')
 
             print('closed stream connection')