Add stale entry deleted from registrar test

By spawning an actor task that immediately shuts down the transport
server and then sleeps, verify that attempting to connect via the
`._discovery.find_actor()` helper delivers `None` for the `Portal`
value.

Relates to #184 and #216

tests/conftest.py

@@ -219,7 +219,8 @@ def daemon(
     arb_addr: tuple[str, int],
 ):
     '''
-    Run a daemon actor as a "remote arbiter".
+    Run a daemon actor as a "remote registrar" and/or plain ol
+    separate actor (service) tree.
 
     '''
     if loglevel in ('trace', 'debug'):

tests/test_discovery.py

@@ -1,6 +1,7 @@
-"""
-Actor "discovery" testing
-"""
+'''
+Discovery subsystem via a "registrar" actor scenarios.
+
+'''
 import os
 import signal
 import platform
@@ -127,7 +128,10 @@ async def unpack_reg(actor_or_portal):
     else:
         msg = await actor_or_portal.run_from_ns('self', 'get_registry')
 
-    return {tuple(key.split('.')): val for key, val in msg.items()}
+    return {
+        tuple(key.split('.')): val
+        for key, val in msg.items()
+    }
 
 
 async def spawn_and_check_registry(
@@ -283,18 +287,22 @@ async def close_chans_before_nursery(
 
                 async with tractor.open_nursery() as tn:
                     portal1 = await tn.start_actor(
-                        name='consumer1', enable_modules=[__name__])
+                        name='consumer1',
+                        enable_modules=[__name__],
+                    )
                     portal2 = await tn.start_actor(
-                        'consumer2', enable_modules=[__name__])
+                        'consumer2',
+                        enable_modules=[__name__],
+                    )
 
-                    # TODO: compact this back as was in last commit once
-                    # 3.9+, see https://github.com/goodboy/tractor/issues/207
-                    async with portal1.open_stream_from(
+                    async with (
+                        portal1.open_stream_from(
                             stream_forever
-                    ) as agen1:
-                        async with portal2.open_stream_from(
+                        ) as agen1,
+                        portal2.open_stream_from(
                             stream_forever
-                        ) as agen2:
+                        ) as agen2,
+                    ):
                         async with trio.open_nursery() as n:
                             n.start_soon(streamer, agen1)
                             n.start_soon(cancel, use_signal, .5)
@@ -331,10 +339,12 @@ def test_close_channel_explicit(
     use_signal,
     arb_addr,
 ):
-    """Verify that closing a stream explicitly and killing the actor's
+    '''
+    Verify that closing a stream explicitly and killing the actor's
     "root nursery" **before** the containing nursery tears down also
     results in subactor(s) deregistering from the arbiter.
-    """
+
+    '''
     with pytest.raises(KeyboardInterrupt):
         trio.run(
             partial(
@@ -347,16 +357,18 @@ def test_close_channel_explicit(
 
 
 @pytest.mark.parametrize('use_signal', [False, True])
-def test_close_channel_explicit_remote_arbiter(
+def test_close_channel_explicit_remote_registrar(
     daemon,
     start_method,
     use_signal,
     arb_addr,
 ):
-    """Verify that closing a stream explicitly and killing the actor's
+    '''
+    Verify that closing a stream explicitly and killing the actor's
     "root nursery" **before** the containing nursery tears down also
     results in subactor(s) deregistering from the arbiter.
-    """
+
+    '''
     with pytest.raises(KeyboardInterrupt):
         trio.run(
             partial(
@@ -366,3 +378,51 @@ def test_close_channel_explicit_remote_arbiter(
                 remote_arbiter=True,
             ),
         )
+
+
+@tractor.context
+async def kill_transport(
+    ctx: tractor.Context,
+) -> None:
+
+    await ctx.started()
+    actor: tractor.Actor = tractor.current_actor()
+    actor.cancel_server()
+    await trio.sleep_forever()
+
+
+
+# @pytest.mark.parametrize('use_signal', [False, True])
+def test_stale_entry_is_deleted(
+    daemon,
+    start_method,
+    arb_addr,
+):
+    '''
+    Ensure that when a stale entry is detected in the registrar's table
+    that the `find_actor()` API takes care of deleting the stale entry
+    and not delivering a bad portal.
+
+    '''
+    async def main():
+
+        name: str = 'transport_fails_actor'
+        regport: tractor.Portal
+        tn: tractor.ActorNursery
+        async with (
+            tractor.open_nursery() as tn,
+            tractor.get_registrar(*arb_addr) as regport,
+        ):
+            ptl: tractor.Portal = await tn.start_actor(
+                name,
+                enable_modules=[__name__],
+            )
+            async with ptl.open_context(
+                kill_transport,
+            ) as (first, ctx):
+                async with tractor.find_actor(name) as maybe_portal:
+                    assert maybe_portal is None
+
+                await ptl.cancel_actor()
+
+    trio.run(main)