Drop unused `Actor._root_n`..

Was failing due to the `.fail_after()` timeout being *too short* and
somehow the new interplay of that with strict-exception groups resulting
in the `TooSlowError` never raising but instead an eg with the embedded
`AssertionError`?? I still don't really get it honestly..

I've written up lengthy notes around the different `delay` settings that
can be used to see the diff outcomes, the failing case being the one
i still don't really grok and think is justification for `trio` to
bubble inner `Cancelled`s differently possibly?

For now i've included the original failing case as an `xfail`
parametrization for now which will hopefully drive a follow lowlevel
`trio` test in `test_trioisms`!

tests/test_cancellation.py

@@ -546,40 +546,123 @@ def test_cancel_via_SIGINT_other_task(
 
 async def spin_for(period=3):
     "Sync sleep."
+    print(f'sync sleeping in sub-sub for {period}\n')
     time.sleep(period)
 
 
-async def spawn():
-    async with tractor.open_nursery() as tn:
-        await tn.run_in_actor(
+async def spawn_sub_with_sync_blocking_task():
+    async with tractor.open_nursery() as an:
+        print('starting sync blocking subactor..\n')
+        await an.run_in_actor(
             spin_for,
             name='sleeper',
         )
+        print('exiting first subactor layer..\n')
 
 
+@pytest.mark.parametrize(
+    'man_cancel_outer',
+    [
+        False,  # passes if delay != 2
+
+        # always causes an unexpected eg-w-embedded-assert-err?
+        pytest.param(True,
+             marks=pytest.mark.xfail(
+                 reason=(
+                    'always causes an unexpected eg-w-embedded-assert-err?'
+                )
+            ),
+        ),
+    ],
+)
 @no_windows
 def test_cancel_while_childs_child_in_sync_sleep(
-    loglevel,
-    start_method,
-    spawn_backend,
+    loglevel: str,
+    start_method: str,
+    spawn_backend: str,
+    debug_mode: bool,
+    reg_addr: tuple,
+    man_cancel_outer: bool,
 ):
-    """Verify that a child cancelled while executing sync code is torn
+    '''
+    Verify that a child cancelled while executing sync code is torn
     down even when that cancellation is triggered by the parent
     2 nurseries "up".
-    """
+
+    Though the grandchild should stay blocking its actor runtime, its
+    parent should issue a "zombie reaper" to hard kill it after
+    sufficient timeout.
+
+    '''
     if start_method == 'forkserver':
         pytest.skip("Forksever sux hard at resuming from sync sleep...")
 
     async def main():
-        with trio.fail_after(2):
+        #
+        # XXX BIG TODO NOTE XXX
+        #
+        # it seems there's a strange race that can happen
+        # where where the fail-after will trigger outer scope
+        # .cancel() which then causes the inner scope to raise,
+        #
+        # BaseExceptionGroup('Exceptions from Trio nursery', [
+        #   BaseExceptionGroup('Exceptions from Trio nursery',
+        #   [
+        #       Cancelled(),
+        #       Cancelled(),
+        #   ]
+        #   ),
+        #   AssertionError('assert 0')
+        # ])
+        #
+        # WHY THIS DOESN'T MAKE SENSE:
+        # ---------------------------
+        # - it should raise too-slow-error when too slow..
+        #  * verified that using simple-cs and manually cancelling
+        #    you get same outcome -> indicates that the fail-after
+        #    can have its TooSlowError overriden!
+        #  |_ to check this it's easy, simplly decrease the timeout
+        #     as per the var below.
+        #
+        # - when using the manual simple-cs the outcome is different
+        #   DESPITE the `assert 0` which means regardless of the
+        #   inner scope effectively failing in the same way, the
+        #   bubbling up **is NOT the same**.
+        #
+        # delays trigger diff outcomes..
+        # ---------------------------
+        # as seen by uncommenting various lines below there is from
+        # my POV an unexpected outcome due to the delay=2 case.
+        #
+        # delay = 1  # no AssertionError in eg, TooSlowError raised.
+        # delay = 2  # is AssertionError in eg AND no TooSlowError !?
+        delay = 4  # is AssertionError in eg AND no _cs cancellation.
+
+        with trio.fail_after(delay) as _cs:
+        # with trio.CancelScope() as cs:
+        # ^XXX^ can be used instead to see same outcome.
+
             async with (
-                tractor.open_nursery() as an
+                # tractor.trionics.collapse_eg(),  # doesn't help
+                tractor.open_nursery(
+                    hide_tb=False,
+                    debug_mode=debug_mode,
+                    registry_addrs=[reg_addr],
+                ) as an,
             ):
                 await an.run_in_actor(
-                    spawn,
-                    name='spawn',
+                    spawn_sub_with_sync_blocking_task,
+                    name='sync_blocking_sub',
                 )
                 await trio.sleep(1)
+
+                if man_cancel_outer:
+                    print('Cancelling manually in root')
+                    _cs.cancel()
+
+                # trigger exc-srced taskc down
+                # the actor tree.
+                print('RAISING IN ROOT')
                 assert 0
 
     with pytest.raises(AssertionError):

tests/test_clustering.py

@@ -13,26 +13,24 @@ MESSAGE = 'tractoring at full speed'
 def test_empty_mngrs_input_raises() -> None:
 
     async def main():
-        with trio.fail_after(1):
+        with trio.fail_after(3):
             async with (
                 open_actor_cluster(
                     modules=[__name__],
 
                     # NOTE: ensure we can passthrough runtime opts
-                    loglevel='info',
-                    # debug_mode=True,
+                    loglevel='cancel',
+                    debug_mode=False,
 
                 ) as portals,
 
-                gather_contexts(
-                    # NOTE: it's the use of inline-generator syntax
-                    # here that causes the empty input.
-                    mngrs=(
-                        p.open_context(worker) for p in portals.values()
-                    ),
-                ),
+                gather_contexts(mngrs=()),
             ):
-                assert 0
+                # should fail before this?
+                assert portals
+
+                # test should fail if we mk it here!
+                assert 0, 'Should have raised val-err !?'
 
     with pytest.raises(ValueError):
         trio.run(main)

tractor/_clustering.py

@@ -55,10 +55,17 @@ async def open_actor_cluster(
         raise ValueError(
             'Number of names is {len(names)} but count it {count}')
 
-    async with tractor.open_nursery(
-        **runtime_kwargs,
-    ) as an:
-        async with trio.open_nursery() as n:
+    async with (
+        # tractor.trionics.collapse_eg(),
+        tractor.open_nursery(
+            **runtime_kwargs,
+        ) as an
+    ):
+        async with (
+            # tractor.trionics.collapse_eg(),
+            trio.open_nursery() as tn,
+            tractor.trionics.maybe_raise_from_masking_exc()
+        ):
             uid = tractor.current_actor().uid
 
             async def _start(name: str) -> None:
@@ -69,9 +76,8 @@ async def open_actor_cluster(
                 )
 
             for name in names:
-                n.start_soon(_start, name)
+                tn.start_soon(_start, name)
 
         assert len(portals) == count
         yield portals
-
         await an.cancel(hard_kill=hard_kill)

tractor/_runtime.py

@@ -174,7 +174,6 @@ class Actor:
     msg_buffer_size: int = 2**6
 
     # nursery placeholders filled in by `async_main()` after fork
-    _root_n: Nursery|None = None
     _service_n: Nursery|None = None
 
     _ipc_server: _server.IPCServer|None = None
@@ -1479,8 +1478,8 @@ async def async_main(
             collapse_eg(),
             trio.open_nursery() as root_tn,
         ):
-            actor._root_n = root_tn
-            assert actor._root_n
+            # actor._root_n = root_tn
+            # assert actor._root_n
 
             ipc_server: _server.IPCServer
             async with (

tractor/trionics/_beg.py

@@ -78,7 +78,6 @@ def collapse_exception_group(
 def get_collapsed_eg(
     beg: BaseExceptionGroup,
 
-    bp: bool = False,
 ) -> BaseException|None:
     '''
     If the input beg can collapse to a single sub-exception which is
@@ -92,7 +91,6 @@ def get_collapsed_eg(
     return maybe_exc
 
 
-
 @acm
 async def collapse_eg(
     hide_tb: bool = True,
@@ -102,6 +100,8 @@ async def collapse_eg(
         # trio.Cancelled,
     },
     add_notes: bool = True,
+
+    bp: bool = False,
 ):
     '''
     If `BaseExceptionGroup` raised in the body scope is
@@ -115,6 +115,20 @@ async def collapse_eg(
         yield
     except BaseExceptionGroup as _beg:
         beg = _beg
+
+        if (
+            bp
+            and
+            len(beg.exceptions) > 1
+        ):
+            import tractor
+            if tractor.current_actor(
+                err_on_no_runtime=False,
+            ):
+                await tractor.pause(shield=True)
+            else:
+                breakpoint()
+
         if (
             (exc := get_collapsed_eg(beg))
             and