Add a multi-task subscriber test

In combination with `.aclose()`-ing the async gen instance returned from
`Portal.run()` this demonstrates the python bug:
https://bugs.python.org/issue32526

I've commented out the line that triggers the bug for now since this
case provides motivation for adding our own `trio.abc.ReceiveMemoryChannel`
implementation to be used instead of async gens directly (returned from
`Portal.run()`) since the latter is **not** task safe.

tests/test_pubsub.py

@@ -4,7 +4,6 @@ from itertools import cycle
 import pytest
 import trio
 import tractor
-from async_generator import aclosing
 from tractor.testing import tractor_test
 
 
@@ -30,10 +29,10 @@ def is_even(i):
 
 
 @tractor.msg.pub
-async def pubber(get_topics):
+async def pubber(get_topics, seed=10):
     ss = tractor.current_actor().statespace
 
-    for i in cycle(range(10)):
+    for i in cycle(range(seed)):
 
         # ensure topic subscriptions are as expected
         ss['get_topics'] = get_topics
@@ -42,7 +41,11 @@ async def pubber(get_topics):
         await trio.sleep(0.1)
 
 
-async def subs(which, pub_actor_name):
+async def subs(
+    which, pub_actor_name, seed=10,
+    portal=None,
+    task_status=trio.TASK_STATUS_IGNORED,
+):
     if len(which) == 1:
         if which[0] == 'even':
             pred = is_even
@@ -54,11 +57,43 @@ async def subs(which, pub_actor_name):
             return isinstance(i, int)
 
     async with tractor.find_actor(pub_actor_name) as portal:
-        agen = await portal.run(__name__, 'pubber', topics=which)
-        async with aclosing(agen) as agen:
+        agen = await portal.run(
+            __name__, 'pubber',
+            topics=which,
+            seed=seed,
+        )
+        task_status.started(agen)
+        times = 10
+        count = 0
+        await agen.__anext__()
+        async for pkt in agen:
+            for topic, value in pkt.items():
+                assert pred(value)
+            count += 1
+            if count >= times:
+                break
+
+        await agen.aclose()
+
+        agen = await portal.run(
+            __name__, 'pubber',
+            topics=['odd'],
+            seed=seed,
+        )
+
+        await agen.__anext__()
+        count = 0
+        # async with aclosing(agen) as agen:
+        try:
             async for pkt in agen:
                 for topic, value in pkt.items():
-                    assert pred(value)
+                    pass
+                    # assert pred(value)
+                count += 1
+                if count >= times:
+                    break
+        finally:
+            await agen.aclose()
 
 
 @tractor.msg.pub(tasks=['one', 'two'])
@@ -101,7 +136,7 @@ async def test_required_args(callwith_expecterror):
     'pub_actor',
     ['streamer', 'arbiter']
 )
-def test_pubsub_multi_actor_subs(
+def test_multi_actor_subs_arbiter_pub(
     loglevel,
     arb_addr,
     pub_actor,
@@ -115,7 +150,7 @@ def test_pubsub_multi_actor_subs(
 
             name = 'arbiter'
 
-            if pub_actor is 'streamer':
+            if pub_actor == 'streamer':
                 # start the publisher as a daemon
                 master_portal = await n.start_actor(
                     'streamer',
@@ -131,7 +166,7 @@ def test_pubsub_multi_actor_subs(
                 # block until 2nd actor is initialized
                 pass
 
-            if pub_actor is 'arbiter':
+            if pub_actor == 'arbiter':
                 # wait for publisher task to be spawned in a local RPC task
                 while not ss.get('get_topics'):
                     await trio.sleep(0.1)
@@ -144,7 +179,7 @@ def test_pubsub_multi_actor_subs(
                 # block until 2nd actor is initialized
                 pass
 
-            if pub_actor is 'arbiter':
+            if pub_actor == 'arbiter':
                 start = time.time()
                 while 'odd' not in get_topics():
                     await trio.sleep(0.1)
@@ -166,13 +201,13 @@ def test_pubsub_multi_actor_subs(
             await even_portal.cancel_actor()
             await trio.sleep(0.5)
 
-            if pub_actor is 'arbiter':
+            if pub_actor == 'arbiter':
                 assert 'even' not in get_topics()
 
             await odd_portal.cancel_actor()
             await trio.sleep(1)
 
-            if pub_actor is 'arbiter':
+            if pub_actor == 'arbiter':
                 while get_topics():
                     await trio.sleep(0.1)
                     if time.time() - start > 1:
@@ -185,3 +220,43 @@ def test_pubsub_multi_actor_subs(
         arbiter_addr=arb_addr,
         rpc_module_paths=[__name__],
     )
+
+
+def test_single_subactor_pub_multitask_subs(
+    loglevel,
+    arb_addr,
+):
+    async def main():
+
+        async with tractor.open_nursery() as n:
+
+            portal = await n.start_actor(
+                'streamer',
+                rpc_module_paths=[__name__],
+            )
+            async with tractor.wait_for_actor('streamer'):
+                # block until 2nd actor is initialized
+                pass
+
+            async with trio.open_nursery() as tn:
+                agen = await tn.start(subs, ['even'], 'streamer')
+
+                await trio.sleep(0.1)
+                tn.start_soon(subs, ['even'], 'streamer')
+
+                # XXX this will trigger the python bug:
+                # https://bugs.python.org/issue32526
+                # await agen.aclose()
+
+                await trio.sleep(0.1)
+                tn.start_soon(subs, ['even'], 'streamer')
+                await trio.sleep(0.1)
+                tn.start_soon(subs, ['even'], 'streamer')
+
+            await portal.cancel_actor()
+
+    tractor.run(
+        main,
+        arbiter_addr=arb_addr,
+        rpc_module_paths=[__name__],
+    )