Bump "task-manager(-nursery)" naming, add logging

Namely just renaming any `trio.Nursery` instances to `tn`, the primary
`@acm`-API to `.trionics.open_taskman()` and change out all `print()`s
for logger instances with 'info' level enabled by the mod-script usage.

examples/trio/lockacquire_not_unmasked.py

@@ -0,0 +1,85 @@
+from contextlib import (
+    asynccontextmanager as acm,
+)
+from functools import partial
+
+import tractor
+import trio
+
+
+log = tractor.log.get_logger(
+    name=__name__
+)
+
+_lock: trio.Lock|None = None
+
+
+@acm
+async def acquire_singleton_lock(
+) -> None:
+    global _lock
+    if _lock is None:
+        log.info('Allocating LOCK')
+        _lock = trio.Lock()
+
+    log.info('TRYING TO LOCK ACQUIRE')
+    async with _lock:
+        log.info('ACQUIRED')
+        yield _lock
+
+    log.info('RELEASED')
+
+
+
+async def hold_lock_forever(
+    task_status=trio.TASK_STATUS_IGNORED
+):
+    async with (
+        tractor.trionics.maybe_raise_from_masking_exc(),
+        acquire_singleton_lock() as lock,
+    ):
+        task_status.started(lock)
+        await trio.sleep_forever()
+
+
+async def main(
+    ignore_special_cases: bool,
+    loglevel: str = 'info',
+    debug_mode: bool = True,
+):
+    async with (
+        trio.open_nursery() as tn,
+
+        # tractor.trionics.maybe_raise_from_masking_exc()
+        # ^^^ XXX NOTE, interestingly putting the unmasker
+        # here does not exhibit the same behaviour ??
+    ):
+        if not ignore_special_cases:
+            from tractor.trionics import _taskc
+            _taskc._mask_cases.clear()
+
+        _lock = await tn.start(
+            hold_lock_forever,
+        )
+        with trio.move_on_after(0.2):
+            await tn.start(
+                hold_lock_forever,
+            )
+
+        tn.cancel_scope.cancel()
+
+
+# XXX, manual test as script
+if __name__ == '__main__':
+    tractor.log.get_console_log(level='info')
+    for case in [True, False]:
+        log.info(
+            f'\n'
+            f'------ RUNNING SCRIPT TRIAL ------\n'
+            f'ignore_special_cases: {case!r}\n'
+        )
+        trio.run(partial(
+            main,
+            ignore_special_cases=case,
+            loglevel='info',
+        ))

examples/trio/send_chan_aclose_masks_beg.py

@@ -0,0 +1,195 @@
+from contextlib import (
+    contextmanager as cm,
+    # TODO, any diff in async case(s)??
+    # asynccontextmanager as acm,
+)
+from functools import partial
+
+import tractor
+import trio
+
+
+log = tractor.log.get_logger(
+    name=__name__
+)
+
+
+@cm
+def teardown_on_exc(
+    raise_from_handler: bool = False,
+):
+    '''
+    You could also have a teardown handler which catches any exc and
+    does some required teardown. In this case the problem is
+    compounded UNLESS you ensure the handler's scope is OUTSIDE the
+    `ux.aclose()`.. that is in the caller's enclosing scope.
+
+    '''
+    try:
+        yield
+    except BaseException as _berr:
+        berr = _berr
+        log.exception(
+            f'Handling termination teardown in child due to,\n'
+            f'{berr!r}\n'
+        )
+        if raise_from_handler:
+            # XXX teardown ops XXX
+            # on termination these steps say need to be run to
+            # ensure wider system consistency (like the state of
+            # remote connections/services).
+            #
+            # HOWEVER, any bug in this teardown code is also
+            # masked by the `tx.aclose()`!
+            # this is also true if `_tn.cancel_scope` is
+            # `.cancel_called` by the parent in a graceful
+            # request case..
+
+            # simulate a bug in teardown handler.
+            raise RuntimeError(
+                'woopsie teardown bug!'
+            )
+
+        raise  # no teardown bug.
+
+
+async def finite_stream_to_rent(
+    tx: trio.abc.SendChannel,
+    child_errors_mid_stream: bool,
+    raise_unmasked: bool,
+
+    task_status: trio.TaskStatus[
+        trio.CancelScope,
+    ] = trio.TASK_STATUS_IGNORED,
+):
+    async with (
+        # XXX without this unmasker the mid-streaming RTE is never
+        # reported since it is masked by the `tx.aclose()`
+        # call which in turn raises `Cancelled`!
+        #
+        # NOTE, this is WITHOUT doing any exception handling
+        # inside the child  task!
+        #
+        # TODO, uncomment next LoC to see the supprsessed beg[RTE]!
+        tractor.trionics.maybe_raise_from_masking_exc(
+            raise_unmasked=raise_unmasked,
+        ),
+
+        tx as tx,  # .aclose() is the guilty masker chkpt!
+
+        # XXX, this ONLY matters in the
+        # `child_errors_mid_stream=False` case oddly!?
+        # THAT IS, if no tn is opened in that case then the
+        # test will not fail; it raises the RTE correctly?
+        #
+        # -> so it seems this new scope somehow affects the form of
+        #    eventual in the parent EG?
+        tractor.trionics.maybe_open_nursery(
+            nursery=(
+                None
+                if not child_errors_mid_stream
+                else True
+            ),
+        ) as _tn,
+    ):
+        # pass our scope back to parent for supervision\
+        # control.
+        cs: trio.CancelScope|None = (
+            None
+            if _tn is True
+            else _tn.cancel_scope
+        )
+        task_status.started(cs)
+
+        with teardown_on_exc(
+            raise_from_handler=not child_errors_mid_stream,
+        ):
+            for i in range(100):
+                log.debug(
+                    f'Child tx {i!r}\n'
+                )
+                if (
+                    child_errors_mid_stream
+                    and
+                    i == 66
+                ):
+                    # oh wait but WOOPS there's a bug
+                    # in that teardown code!?
+                    raise RuntimeError(
+                        'woopsie, a mid-streaming bug!?'
+                    )
+
+                await tx.send(i)
+
+
+async def main(
+    # TODO! toggle this for the 2 cases!
+    # 1. child errors mid-stream while parent is also requesting
+    #   (graceful) cancel of that child streamer.
+    #
+    # 2. child contains a teardown handler which contains a
+    #   bug and raises.
+    #
+    child_errors_mid_stream: bool,
+
+    raise_unmasked: bool = False,
+    loglevel: str = 'info',
+):
+    tractor.log.get_console_log(level=loglevel)
+
+    # the `.aclose()` being checkpoints on these
+    # is the source of the problem..
+    tx, rx = trio.open_memory_channel(1)
+
+    async with (
+        tractor.trionics.collapse_eg(),
+        trio.open_nursery() as tn,
+        rx as rx,
+    ):
+        _child_cs = await tn.start(
+            partial(
+                finite_stream_to_rent,
+                child_errors_mid_stream=child_errors_mid_stream,
+                raise_unmasked=raise_unmasked,
+                tx=tx,
+            )
+        )
+        async for msg in rx:
+            log.debug(
+                f'Rent rx {msg!r}\n'
+            )
+
+            # simulate some external cancellation
+            # request **JUST BEFORE** the child errors.
+            if msg == 65:
+                log.cancel(
+                    f'Cancelling parent on,\n'
+                    f'msg={msg}\n'
+                    f'\n'
+                    f'Simulates OOB cancel request!\n'
+                )
+                tn.cancel_scope.cancel()
+
+
+# XXX, manual test as script
+if __name__ == '__main__':
+    tractor.log.get_console_log(level='info')
+    for case in [True, False]:
+        log.info(
+            f'\n'
+            f'------ RUNNING SCRIPT TRIAL ------\n'
+            f'child_errors_midstream: {case!r}\n'
+        )
+        try:
+            trio.run(partial(
+                main,
+                child_errors_mid_stream=case,
+                # raise_unmasked=True,
+                loglevel='info',
+            ))
+        except Exception as _exc:
+            exc = _exc
+            log.exception(
+                'Should have raised an RTE or Cancelled?\n'
+            )
+            breakpoint()

tests/test_docs_examples.py

@@ -95,6 +95,7 @@ def run_example_in_subproc(
             and 'integration' not in p[0]
             and 'advanced_faults' not in p[0]
             and 'multihost' not in p[0]
+            and 'trio' not in p[0]
         )
     ],
     ids=lambda t: t[1],

tests/test_inter_peer_cancellation.py

@@ -24,14 +24,10 @@ from tractor._testing import (
 )
 
 # XXX TODO cases:
-# - [ ] peer cancelled itself - so other peers should
-#   get errors reflecting that the peer was itself the .canceller?
-
 # - [x] WE cancelled the peer and thus should not see any raised
 #   `ContextCancelled` as it should be reaped silently?
 #   => pretty sure `test_context_stream_semantics::test_caller_cancels()`
 #      already covers this case?
-
 # - [x] INTER-PEER: some arbitrary remote peer cancels via
 #   Portal.cancel_actor().
 #   => all other connected peers should get that cancel requesting peer's
@@ -44,16 +40,6 @@ from tractor._testing import (
 #   that also spawned a remote task task in that same peer-parent.
 
 
-# def test_self_cancel():
-#     '''
-#     2 cases:
-#     - calls `Actor.cancel()` locally in some task
-#     - calls LocalPortal.cancel_actor()` ?
-
-#     '''
-#     ...
-
-
 @tractor.context
 async def open_stream_then_sleep_forever(
     ctx: Context,
@@ -806,7 +792,7 @@ async def basic_echo_server(
     ctx: Context,
     peer_name: str = 'wittle_bruv',
 
-    err_after: int|None = None,
+    err_after_imsg: int|None = None,
 
 ) -> None:
     '''
@@ -835,8 +821,9 @@ async def basic_echo_server(
             await ipc.send(resp)
 
             if (
-                err_after
-                and i > err_after
+                err_after_imsg
+                and
+                i > err_after_imsg
             ):
                 raise RuntimeError(
                     f'Simulated error in `{peer_name}`'
@@ -978,7 +965,8 @@ async def tell_little_bro(
     actor_name: str,
 
     caller: str = '',
-    err_after: int|None = None,
+    err_after: float|None = None,
+    rng_seed: int = 50,
 ):
     # contact target actor, do a stream dialog.
     async with (
@@ -989,14 +977,18 @@ async def tell_little_bro(
             basic_echo_server,
 
             # XXX proxy any delayed err condition
-            err_after=err_after,
+            err_after_imsg=(
+                err_after * rng_seed
+                if err_after is not None
+                else None
+            ),
         ) as (sub_ctx, first),
 
         sub_ctx.open_stream() as echo_ipc,
     ):
         actor: Actor = current_actor()
         uid: tuple = actor.uid
-        for i in range(100):
+        for i in range(rng_seed):
             msg: tuple = (
                 uid,
                 i,
@@ -1021,13 +1013,13 @@ async def tell_little_bro(
 )
 @pytest.mark.parametrize(
     'raise_sub_spawn_error_after',
-    [None, 50],
+    [None, 0.5],
 )
 def test_peer_spawns_and_cancels_service_subactor(
     debug_mode: bool,
     raise_client_error: str,
     reg_addr: tuple[str, int],
-    raise_sub_spawn_error_after: int|None,
+    raise_sub_spawn_error_after: float|None,
 ):
     # NOTE: this tests for the modden `mod wks open piker` bug
     # discovered as part of implementing workspace ctx
@@ -1041,6 +1033,7 @@ def test_peer_spawns_and_cancels_service_subactor(
     #   and the server's spawned child should cancel and terminate!
     peer_name: str = 'little_bro'
 
+
     def check_inner_rte(rae: RemoteActorError):
         '''
         Validate the little_bro's relayed inception!
@@ -1134,8 +1127,7 @@ def test_peer_spawns_and_cancels_service_subactor(
                         )
 
                     try:
-                        res = await client_ctx.result(hide_tb=False)
-
+                        res = await client_ctx.wait_for_result(hide_tb=False)
                         # in remote (relayed inception) error
                         # case, we should error on the line above!
                         if raise_sub_spawn_error_after:
@@ -1146,6 +1138,23 @@ def test_peer_spawns_and_cancels_service_subactor(
                         assert isinstance(res, ContextCancelled)
                         assert client_ctx.cancel_acked
                         assert res.canceller == root.uid
+                        assert not raise_sub_spawn_error_after
+
+                        # cancelling the spawner sub should
+                        # transitively cancel it's sub, the little
+                        # bruv.
+                        print('root cancelling server/client sub-actors')
+                        await spawn_ctx.cancel()
+                        async with tractor.find_actor(
+                            name=peer_name,
+                        ) as sub:
+                            assert not sub
+
+                    # XXX, only for tracing
+                    # except BaseException as _berr:
+                    #     berr = _berr
+                    #     await tractor.pause(shield=True)
+                    #     raise berr
 
                     except RemoteActorError as rae:
                         _err = rae
@@ -1174,19 +1183,8 @@ def test_peer_spawns_and_cancels_service_subactor(
                         raise
                         # await tractor.pause()
 
-                    else:
-                        assert not raise_sub_spawn_error_after
-
-                        # cancelling the spawner sub should
-                        # transitively cancel it's sub, the little
-                        # bruv.
-                        print('root cancelling server/client sub-actors')
-                        await spawn_ctx.cancel()
-                        async with tractor.find_actor(
-                            name=peer_name,
-                        ) as sub:
-                            assert not sub
 
+                    # await tractor.pause()
                     # await server.cancel_actor()
 
             except RemoteActorError as rae:
@@ -1199,7 +1197,7 @@ def test_peer_spawns_and_cancels_service_subactor(
 
             # since we called `.cancel_actor()`, `.cancel_ack`
             # will not be set on the ctx bc `ctx.cancel()` was not
-            # called directly fot this confext.
+            # called directly for this confext.
             except ContextCancelled as ctxc:
                 _ctxc = ctxc
                 print(
@@ -1239,12 +1237,19 @@ def test_peer_spawns_and_cancels_service_subactor(
 
                 # assert spawn_ctx.cancelled_caught
 
+    async def _main():
+        with trio.fail_after(
+            3 if not debug_mode
+            else 999
+        ):
+            await main()
+
     if raise_sub_spawn_error_after:
         with pytest.raises(RemoteActorError) as excinfo:
-            trio.run(main)
+            trio.run(_main)
 
         rae: RemoteActorError = excinfo.value
         check_inner_rte(rae)
 
     else:
-        trio.run(main)
+        trio.run(_main)

tests/test_oob_cancellation.py

@@ -0,0 +1,239 @@
+'''
+Define the details of inter-actor "out-of-band" (OoB) cancel
+semantics, that is how cancellation works when a cancel request comes
+from the different concurrency (primitive's) "layer" then where the
+eventual `trio.Task` actually raises a signal.
+
+'''
+from functools import partial
+# from contextlib import asynccontextmanager as acm
+# import itertools
+
+import pytest
+import trio
+import tractor
+from tractor import (  # typing
+    ActorNursery,
+    Portal,
+    Context,
+    # ContextCancelled,
+    # RemoteActorError,
+)
+# from tractor._testing import (
+#     tractor_test,
+#     expect_ctxc,
+# )
+
+# XXX TODO cases:
+# - [ ] peer cancelled itself - so other peers should
+#   get errors reflecting that the peer was itself the .canceller?
+
+# def test_self_cancel():
+#     '''
+#     2 cases:
+#     - calls `Actor.cancel()` locally in some task
+#     - calls LocalPortal.cancel_actor()` ?
+#
+# things to ensure!
+# -[ ] the ctxc raised in a child should ideally show the tb of the
+#     underlying `Cancelled` checkpoint, i.e.
+#     `raise scope_error from ctxc`?
+#
+# -[ ] a self-cancelled context, if not allowed to block on
+#     `ctx.result()` at some point will hang since the `ctx._scope`
+#     is never `.cancel_called`; cases for this include,
+#     - an `open_ctx()` which never starteds before being OoB actor
+#       cancelled.
+#       |_ parent task will be blocked in `.open_context()` for the
+#         `Started` msg, and when the OoB ctxc arrives `ctx._scope`
+#         will never have been signalled..
+
+#     '''
+#     ...
+
+# TODO, sanity test against the case in `/examples/trio/lockacquire_not_unmasked.py`
+# but with the `Lock.acquire()` from a `@context` to ensure the
+# implicit ignore-case-non-unmasking.
+#
+# @tractor.context
+# async def acquire_actor_global_lock(
+#     ctx: tractor.Context,
+#     ignore_special_cases: bool,
+# ):
+
+#     async with maybe_unmask_excs(
+#         ignore_special_cases=ignore_special_cases,
+#     ):
+#         await ctx.started('locked')
+
+#     # block til cancelled
+#     await trio.sleep_forever()
+
+
+@tractor.context
+async def sleep_forever(
+    ctx: tractor.Context,
+    # ignore_special_cases: bool,
+    do_started: bool,
+):
+
+    # async with maybe_unmask_excs(
+    #     ignore_special_cases=ignore_special_cases,
+    # ):
+    #     await ctx.started('locked')
+    if do_started:
+        await ctx.started()
+
+    # block til cancelled
+    print('sleepin on child-side..')
+    await trio.sleep_forever()
+
+
+@pytest.mark.parametrize(
+    'cancel_ctx',
+    [True, False],
+)
+def test_cancel_ctx_with_parent_side_entered_in_bg_task(
+    debug_mode: bool,
+    loglevel: str,
+    cancel_ctx: bool,
+):
+    '''
+    The most "basic" out-of-band-task self-cancellation case where
+    `Portal.open_context()` is entered in a bg task and the
+    parent-task (of the containing nursery) calls `Context.cancel()`
+    without the child knowing; the `Context._scope` should be
+    `.cancel_called` when the IPC ctx's child-side relays
+    a `ContextCancelled` with a `.canceller` set to the parent
+    actor('s task).
+
+    '''
+    async def main():
+        with trio.fail_after(
+            2 if not debug_mode else 999,
+        ):
+            an: ActorNursery
+            async with (
+                tractor.open_nursery(
+                    debug_mode=debug_mode,
+                    loglevel='devx',
+                    enable_stack_on_sig=True,
+                ) as an,
+                trio.open_nursery() as tn,
+            ):
+                ptl: Portal = await an.start_actor(
+                    'sub',
+                    enable_modules=[__name__],
+                )
+
+                async def _open_ctx_async(
+                    do_started: bool = True,
+                    task_status=trio.TASK_STATUS_IGNORED,
+                ):
+                    # do we expect to never enter the
+                    # `.open_context()` below.
+                    if not do_started:
+                        task_status.started()
+
+                    async with ptl.open_context(
+                        sleep_forever,
+                        do_started=do_started,
+                    ) as (ctx, first):
+                        task_status.started(ctx)
+                        await trio.sleep_forever()
+
+                # XXX, this is the key OoB part!
+                #
+                # - start the `.open_context()` in a bg task which
+                #   blocks inside the embedded scope-body,
+                #
+                # -  when we call `Context.cancel()` it **is
+                #   not** from the same task which eventually runs
+                #   `.__aexit__()`,
+                #
+                # - since the bg "opener" task will be in
+                #   a `trio.sleep_forever()`, it must be interrupted
+                #   by the `ContextCancelled` delivered from the
+                #   child-side; `Context._scope: CancelScope` MUST
+                #   be `.cancel_called`!
+                #
+                print('ASYNC opening IPC context in subtask..')
+                maybe_ctx: Context|None = await tn.start(partial(
+                    _open_ctx_async,
+                ))
+
+                if (
+                    maybe_ctx
+                    and
+                    cancel_ctx
+                ):
+                    print('cancelling first IPC ctx!')
+                    await maybe_ctx.cancel()
+
+                # XXX, note that despite `maybe_context.cancel()`
+                # being called above, it's the parent (bg) task
+                # which was originally never interrupted in
+                # the `ctx._scope` body due to missing case logic in
+                # `ctx._maybe_cancel_and_set_remote_error()`.
+                #
+                # It didn't matter that the subactor process was
+                # already terminated and reaped, nothing was
+                # cancelling the ctx-parent task's scope!
+                #
+                print('cancelling subactor!')
+                await ptl.cancel_actor()
+
+                if maybe_ctx:
+                    try:
+                        await maybe_ctx.wait_for_result()
+                    except tractor.ContextCancelled as ctxc:
+                        assert not cancel_ctx
+                        assert (
+                            ctxc.canceller
+                            ==
+                            tractor.current_actor().aid.uid
+                        )
+                        # don't re-raise since it'll trigger
+                        # an EG from the above tn.
+
+    if cancel_ctx:
+        # graceful self-cancel
+        trio.run(main)
+
+    else:
+        # ctx parent task should see OoB ctxc due to
+        # `ptl.cancel_actor()`.
+        with pytest.raises(tractor.ContextCancelled) as excinfo:
+            trio.run(main)
+
+        assert 'root' in excinfo.value.canceller[0]
+
+
+# def test_parent_actor_cancels_subactor_with_gt1_ctxs_open_to_it(
+#     debug_mode: bool,
+#     loglevel: str,
+# ):
+#     '''
+#     Demos OoB cancellation from the perspective of a ctx opened with
+#     a child subactor where the parent cancels the child at the "actor
+#     layer" using `Portal.cancel_actor()` and thus the
+#     `ContextCancelled.canceller` received by the ctx's parent-side
+#     task will appear to be a "self cancellation" even though that
+#     specific task itself was not cancelled and thus
+#     `Context.cancel_called ==False`.
+#     '''
+                # TODO, do we have an existing implied ctx
+                # cancel test like this?
+                # with trio.move_on_after(0.5):# as cs:
+                #     await _open_ctx_async(
+                #         do_started=False,
+                #     )
+
+
+                # in-line ctx scope should definitely raise
+                # a ctxc with `.canceller = 'root'`
+                # async with ptl.open_context(
+                #     sleep_forever,
+                #     do_started=True,
+                # ) as pair:
+

tests/test_trioisms.py

@@ -6,11 +6,18 @@ want to see changed.
 from contextlib import (
     asynccontextmanager as acm,
 )
+from types import ModuleType
+
+from functools import partial
 
 import pytest
+from _pytest import pathlib
 from tractor.trionics import collapse_eg
 import trio
 from trio import TaskStatus
+from tractor._testing import (
+    examples_dir,
+)
 
 
 @pytest.mark.parametrize(
@@ -106,8 +113,9 @@ def test_acm_embedded_nursery_propagates_enter_err(
     debug_mode: bool,
 ):
     '''
-    Demo how a masking `trio.Cancelled` could be handled by unmasking from the
-    `.__context__` field when a user (by accident) re-raises from a `finally:`.
+    Demo how a masking `trio.Cancelled` could be handled by unmasking
+    from the `.__context__` field when a user (by accident) re-raises
+    from a `finally:`.
 
     '''
     import tractor
@@ -117,11 +125,9 @@ def test_acm_embedded_nursery_propagates_enter_err(
         async with (
             trio.open_nursery() as tn,
             tractor.trionics.maybe_raise_from_masking_exc(
-                tn=tn,
                 unmask_from=(
-                    trio.Cancelled
-                    if unmask_from_canc
-                    else None
+                    (trio.Cancelled,) if unmask_from_canc
+                    else ()
                 ),
             )
         ):
@@ -136,8 +142,7 @@ def test_acm_embedded_nursery_propagates_enter_err(
         with tractor.devx.maybe_open_crash_handler(
             pdb=debug_mode,
         ) as bxerr:
-            if bxerr:
-                assert not bxerr.value
+            assert not bxerr.value
 
             async with (
                 wraps_tn_that_always_cancels() as tn,
@@ -145,11 +150,12 @@ def test_acm_embedded_nursery_propagates_enter_err(
                 assert not tn.cancel_scope.cancel_called
                 assert 0
 
-        assert (
-            (err := bxerr.value)
-            and
-            type(err) is AssertionError
-        )
+        if debug_mode:
+            assert (
+                (err := bxerr.value)
+                and
+                type(err) is AssertionError
+            )
 
     with pytest.raises(ExceptionGroup) as excinfo:
         trio.run(_main)
@@ -160,13 +166,13 @@ def test_acm_embedded_nursery_propagates_enter_err(
     assert len(assert_eg.exceptions) == 1
 
 
-
 def test_gatherctxs_with_memchan_breaks_multicancelled(
     debug_mode: bool,
 ):
     '''
-    Demo how a using an `async with sndchan` inside a `.trionics.gather_contexts()` task
-    will break a strict-eg-tn's multi-cancelled absorption..
+    Demo how a using an `async with sndchan` inside
+    a `.trionics.gather_contexts()` task will break a strict-eg-tn's
+    multi-cancelled absorption..
 
     '''
     from tractor import (
@@ -192,7 +198,6 @@ def test_gatherctxs_with_memchan_breaks_multicancelled(
                 f'Closed {task!r}\n'
             )
 
-
     async def main():
         async with (
             # XXX should ensure ONLY the KBI
@@ -213,3 +218,85 @@ def test_gatherctxs_with_memchan_breaks_multicancelled(
 
     with pytest.raises(KeyboardInterrupt):
         trio.run(main)
+
+
+@pytest.mark.parametrize(
+    'raise_unmasked', [
+        True,
+        pytest.param(
+            False,
+            marks=pytest.mark.xfail(
+                reason="see examples/trio/send_chan_aclose_masks.py"
+            )
+        ),
+    ]
+)
+@pytest.mark.parametrize(
+    'child_errors_mid_stream',
+    [True, False],
+)
+def test_unmask_aclose_as_checkpoint_on_aexit(
+    raise_unmasked: bool,
+    child_errors_mid_stream: bool,
+    debug_mode: bool,
+):
+    '''
+    Verify that our unmasker util works over the common case where
+    a mem-chan's `.aclose()` is included in an `@acm` stack
+    and it being currently a checkpoint, can `trio.Cancelled`-mask an embedded
+    exception from user code resulting in a silent failure which
+    appears like graceful cancellation.
+
+    This test suite is mostly implemented as an example script so it
+    could more easily be shared with `trio`-core peeps as `tractor`-less
+    minimum reproducing example.
+
+    '''
+    mod: ModuleType = pathlib.import_path(
+        examples_dir()
+        / 'trio'
+        / 'send_chan_aclose_masks_beg.py',
+        root=examples_dir(),
+        consider_namespace_packages=False,
+    )
+    with pytest.raises(RuntimeError):
+        trio.run(partial(
+            mod.main,
+            raise_unmasked=raise_unmasked,
+            child_errors_mid_stream=child_errors_mid_stream,
+        ))
+
+
+
+@pytest.mark.parametrize(
+    'ignore_special_cases', [
+        True,
+        pytest.param(
+            False,
+            marks=pytest.mark.xfail(
+                reason="see examples/trio/lockacquire_not_umasked.py"
+            )
+        ),
+    ]
+)
+def test_cancelled_lockacquire_in_ipctx_not_unmasked(
+    ignore_special_cases: bool,
+    loglevel: str,
+    debug_mode: bool,
+):
+    mod: ModuleType = pathlib.import_path(
+        examples_dir()
+        / 'trio'
+        / 'lockacquire_not_unmasked.py',
+        root=examples_dir(),
+        consider_namespace_packages=False,
+    )
+    async def _main():
+        with trio.fail_after(2):
+            await mod.main(
+                ignore_special_cases=ignore_special_cases,
+                loglevel=loglevel,
+                debug_mode=debug_mode,
+            )
+
+    trio.run(_main)

tractor/_context.py

@@ -442,25 +442,25 @@ class Context:
         '''
         Records whether cancellation has been requested for this context
         by a call to  `.cancel()` either due to,
-        - either an explicit call by some local task,
+        - an explicit call by some local task,
         - or an implicit call due to an error caught inside
-          the ``Portal.open_context()`` block.
+          the `Portal.open_context()` block.
 
         '''
         return self._cancel_called
 
-    @cancel_called.setter
-    def cancel_called(self, val: bool) -> None:
-        '''
-        Set the self-cancelled request `bool` value.
+    # XXX, to debug who frickin sets it..
+    # @cancel_called.setter
+    # def cancel_called(self, val: bool) -> None:
+    #     '''
+    #     Set the self-cancelled request `bool` value.
 
-        '''
-        # to debug who frickin sets it..
-        # if val:
-        #     from .devx import pause_from_sync
-        #     pause_from_sync()
+    #     '''
+    #     if val:
+    #         from .devx import pause_from_sync
+    #         pause_from_sync()
 
-        self._cancel_called = val
+    #     self._cancel_called = val
 
     @property
     def canceller(self) -> tuple[str, str]|None:
@@ -635,6 +635,71 @@ class Context:
         '''
         await self.chan.send(Stop(cid=self.cid))
 
+    @property
+    def parent_task(self) -> trio.Task:
+        '''
+        This IPC context's "owning task" which is a `trio.Task`
+        on one of the "sides" of the IPC.
+
+        Note that the "parent_" prefix here refers to the local
+        `trio` task tree using the same interface as
+        `trio.Nursery.parent_task` whereas for IPC contexts,
+        a different cross-actor task hierarchy exists:
+
+        - a "parent"-side which originally entered
+          `Portal.open_context()`,
+
+        - the "child"-side which was spawned and scheduled to invoke
+          a function decorated with `@tractor.context`.
+
+        This task is thus a handle to mem-domain-distinct/per-process
+        `Nursery.parent_task` depending on in which of the above
+        "sides" this context exists.
+
+        '''
+        return self._task
+
+    def _is_blocked_on_rx_chan(self) -> bool:
+        '''
+        Predicate to indicate whether the owner `._task: trio.Task` is
+        currently blocked (by `.receive()`-ing) on its underlying RPC
+        feeder `._rx_chan`.
+
+        This knowledge is highly useful when handling so called
+        "out-of-band" (OoB) cancellation conditions where a peer
+        actor's task transmitted some remote error/cancel-msg and we
+        must know whether to signal-via-cancel currently executing
+        "user-code" (user defined code embedded in `ctx._scope`) or
+        simply to forward the IPC-msg-as-error **without calling**
+        `._scope.cancel()`.
+
+        In the latter case it is presumed that if the owner task is
+        blocking for the next IPC msg, it will eventually receive,
+        process and raise the equivalent local error **without**
+        requiring `._scope.cancel()` to be explicitly called by the
+        *delivering OoB RPC-task* (via `_deliver_msg()`).
+
+        '''
+        # NOTE, see the mem-chan meth-impls for *why* this
+        # logic works,
+        # `trio._channel.MemoryReceiveChannel.receive[_nowait]()`
+        #
+        # XXX realize that this is NOT an
+        # official/will-be-loudly-deprecated API:
+        # - https://trio.readthedocs.io/en/stable/reference-lowlevel.html#trio.lowlevel.Task.custom_sleep_data
+        #  |_https://trio.readthedocs.io/en/stable/reference-lowlevel.html#trio.lowlevel.wait_task_rescheduled
+        #
+        # orig repo intro in the mem-chan change over patch:
+        # - https://github.com/python-trio/trio/pull/586#issuecomment-414039117
+        #  |_https://github.com/python-trio/trio/pull/616
+        #  |_https://github.com/njsmith/trio/commit/98c38cef6f62e731bf8c7190e8756976bface8f0
+        #
+        return (
+            self._task.custom_sleep_data
+            is
+            self._rx_chan
+        )
+
     def _maybe_cancel_and_set_remote_error(
         self,
         error: BaseException,
@@ -787,13 +852,27 @@ class Context:
         if self._canceller is None:
             log.error('Ctx has no canceller set!?')
 
+        cs: trio.CancelScope = self._scope
+
+        # ?TODO? see comment @ .start_remote_task()`
+        #
+        # if not cs:
+        #     from .devx import mk_pdb
+        #     mk_pdb().set_trace()
+        #     raise RuntimeError(
+        #         f'IPC ctx was not be opened prior to remote error delivery !?\n'
+        #         f'{self}\n'
+        #         f'\n'
+        #         f'`Portal.open_context()` must be entered (somewhere) beforehand!\n'
+        #     )
+
         # Cancel the local `._scope`, catch that
         # `._scope.cancelled_caught` and re-raise any remote error
         # once exiting (or manually calling `.wait_for_result()`) the
         # `.open_context()`  block.
-        cs: trio.CancelScope = self._scope
         if (
             cs
+            and not cs.cancel_called
 
             # XXX this is an expected cancel request response
             # message and we **don't need to raise it** in the
@@ -802,8 +881,7 @@ class Context:
             # if `._cancel_called` then `.cancel_acked and .cancel_called`
             # always should be set.
             and not self._is_self_cancelled()
-            and not cs.cancel_called
-            and not cs.cancelled_caught
+            # and not cs.cancelled_caught
         ):
             if (
                 msgerr
@@ -814,7 +892,7 @@ class Context:
                 not self._cancel_on_msgerr
             ):
                 message: str = (
-                    'NOT Cancelling `Context._scope` since,\n'
+                    f'NOT Cancelling `Context._scope` since,\n'
                     f'Context._cancel_on_msgerr = {self._cancel_on_msgerr}\n\n'
                     f'AND we got a msg-type-error!\n'
                     f'{error}\n'
@@ -824,13 +902,43 @@ class Context:
                 # `trio.Cancelled` subtype here ;)
                 # https://github.com/goodboy/tractor/issues/368
                 message: str = 'Cancelling `Context._scope` !\n\n'
-                # from .devx import pause_from_sync
-                # pause_from_sync()
-                self._scope.cancel()
-        else:
-            message: str = 'NOT cancelling `Context._scope` !\n\n'
+                cs.cancel()
+
+        # TODO, explicit condition for OoB (self-)cancellation?
+        # - we called `Portal.cancel_actor()` from this actor
+        #   and the peer ctx task delivered ctxc due to it.
+        # - currently `self._is_self_cancelled()` will be true
+        #   since the ctxc.canceller check will match us even though it
+        #   wasn't from this ctx specifically!
+        elif (
+            cs
+            and self._is_self_cancelled()
+            and not cs.cancel_called
+        ):
+            message: str = (
+                'Cancelling `ctx._scope` due to OoB self-cancel ?!\n'
+                '\n'
+            )
             # from .devx import mk_pdb
             # mk_pdb().set_trace()
+            # TODO XXX, required to fix timeout failure in
+            # `test_cancelled_lockacquire_in_ipctx_not_unmaskeed`
+            #
+
+            # XXX NOTE XXX, this is SUPER SUBTLE!
+            # we only want to cancel our embedded `._scope`
+            # if the ctx's current/using task is NOT blocked
+            # on `._rx_chan.receive()` and on some other
+            # `trio`-checkpoint since in the former case
+            # any `._remote_error` will be relayed through
+            # the rx-chan and appropriately raised by the owning
+            # `._task` directly. IF the owner task is however
+            # blocking elsewhere we need to interrupt it **now**.
+            if not self._is_blocked_on_rx_chan():
+                cs.cancel()
+        else:
+            # rx_stats = self._rx_chan.statistics()
+            message: str = 'NOT cancelling `Context._scope` !\n\n'
 
         fmt_str: str = 'No `self._scope: CancelScope` was set/used ?\n'
         if (
@@ -854,6 +962,7 @@ class Context:
                 +
                 cs_fmt
             )
+
         log.cancel(
             message
             +
@@ -946,8 +1055,9 @@ class Context:
 
         '''
         side: str = self.side
-        # XXX for debug via the `@.setter`
-        self.cancel_called = True
+        self._cancel_called = True
+        # ^ XXX for debug via the `@.setter`
+        # self.cancel_called = True
 
         header: str = (
             f'Cancelling ctx from {side!r}-side\n'
@@ -2011,6 +2121,9 @@ async def open_context_from_portal(
             f'|_{portal.actor}\n'
         )
 
+    # ?TODO? could we move this to inside the `tn` block?
+    # -> would allow doing `ctx.parent_task = tn.parent_task` ?
+    # -> would allow a `if not ._scope: => raise RTE` ?
     ctx: Context = await portal.actor.start_remote_task(
         portal.channel,
         nsf=nsf,
@@ -2037,6 +2150,7 @@ async def open_context_from_portal(
     scope_err: BaseException|None = None
     ctxc_from_child: ContextCancelled|None = None
     try:
+        # from .devx import pause
         async with (
             collapse_eg(),
             trio.open_nursery() as tn,
@@ -2059,6 +2173,10 @@ async def open_context_from_portal(
             # the dialog, the `Error` msg should be raised from the `msg`
             # handling block below.
             try:
+                log.runtime(
+                    f'IPC ctx parent waiting on Started msg..\n'
+                    f'ctx.cid: {ctx.cid!r}\n'
+                )
                 started_msg, first = await ctx._pld_rx.recv_msg(
                     ipc=ctx,
                     expect_msg=Started,
@@ -2067,16 +2185,16 @@ async def open_context_from_portal(
                 )
             except trio.Cancelled as taskc:
                 ctx_cs: trio.CancelScope = ctx._scope
+                log.cancel(
+                    f'IPC ctx was cancelled during "child" task sync due to\n\n'
+                    f'.cid: {ctx.cid!r}\n'
+                    f'.maybe_error: {ctx.maybe_error!r}\n'
+                )
+                # await pause(shield=True)
+
                 if not ctx_cs.cancel_called:
                     raise
 
-                # from .devx import pause
-                # await pause(shield=True)
-
-                log.cancel(
-                    'IPC ctx was cancelled during "child" task sync due to\n\n'
-                    f'{ctx.maybe_error}\n'
-                )
                 # OW if the ctx's scope was cancelled manually,
                 # likely the `Context` was cancelled via a call to
                 # `._maybe_cancel_and_set_remote_error()` so ensure
@@ -2272,13 +2390,16 @@ async def open_context_from_portal(
         match scope_err:
             case trio.Cancelled():
                 logmeth = log.cancel
+                cause: str = 'cancelled'
 
             # XXX explicitly report on any non-graceful-taskc cases
             case _:
+                cause: str = 'errored'
                 logmeth = log.exception
 
         logmeth(
-            f'ctx {ctx.side!r}-side exited with {ctx.repr_outcome()!r}\n'
+            f'ctx {ctx.side!r}-side {cause!r} with,\n'
+            f'{ctx.repr_outcome()!r}\n'
         )
 
         if debug_mode():
@@ -2303,6 +2424,7 @@ async def open_context_from_portal(
         # told us it's cancelled ;p
         if ctxc_from_child is None:
             try:
+                # await pause(shield=True)
                 await ctx.cancel()
             except (
                 trio.BrokenResourceError,
@@ -2459,8 +2581,10 @@ async def open_context_from_portal(
                 log.cancel(
                     f'Context cancelled by local {ctx.side!r}-side task\n'
                     f'c)>\n'
-                    f' |_{ctx._task}\n\n'
-                    f'{repr(scope_err)}\n'
+                    f'  |_{ctx.parent_task}\n'
+                    f'   .cid={ctx.cid!r}\n'
+                    f'\n'
+                    f'{scope_err!r}\n'
                 )
 
             # TODO: should we add a `._cancel_req_received`

tractor/_rpc.py

@@ -654,8 +654,7 @@ async def _invoke(
                 # scope ensures unasking of the `await coro` below
                 # *should* never be interfered with!!
                 maybe_raise_from_masking_exc(
-                    tn=tn,
-                    unmask_from=Cancelled,
+                    unmask_from=(Cancelled,),
                 ) as _mbme,  # maybe boxed masked exc
             ):
                 ctx._scope_nursery = tn

tractor/_supervise.py

@@ -446,12 +446,12 @@ class ActorNursery:
 @acm
 async def _open_and_supervise_one_cancels_all_nursery(
     actor: Actor,
-    tb_hide: bool = False,
+    hide_tb: bool = True,
 
 ) -> typing.AsyncGenerator[ActorNursery, None]:
 
     # normally don't need to show user by default
-    __tracebackhide__: bool = tb_hide
+    __tracebackhide__: bool = hide_tb
 
     outer_err: BaseException|None = None
     inner_err: BaseException|None = None

tractor/hilevel/__init__.py

@@ -0,0 +1,26 @@
+# tractor: structured concurrent "actors".
+# Copyright 2024-eternity Tyler Goodlet.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+'''
+High level design patterns, APIs and runtime extensions built on top
+of the `tractor` runtime core.
+
+'''
+from ._service import (
+    open_service_mngr as open_service_mngr,
+    get_service_mngr as get_service_mngr,
+    ServiceMngr as ServiceMngr,
+)

tractor/hilevel/_service.py

@@ -0,0 +1,592 @@
+# tractor: structured concurrent "actors".
+# Copyright 2024-eternity Tyler Goodlet.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+'''
+Daemon subactor as service(s) management and supervision primitives
+and API.
+
+'''
+from __future__ import annotations
+from contextlib import (
+    asynccontextmanager as acm,
+    # contextmanager as cm,
+)
+from collections import defaultdict
+from dataclasses import (
+    dataclass,
+    field,
+)
+import functools
+import inspect
+from typing import (
+    Callable,
+    Any,
+)
+
+import tractor
+import trio
+from trio import TaskStatus
+from tractor import (
+    log,
+    ActorNursery,
+    current_actor,
+    ContextCancelled,
+    Context,
+    Portal,
+)
+
+log = log.get_logger('tractor')
+
+
+# TODO: implement a `@singleton` deco-API for wrapping the below
+# factory's impl for general actor-singleton use?
+#
+# -[ ] go through the options peeps on SO did?
+#  * https://stackoverflow.com/questions/6760685/what-is-the-best-way-of-implementing-singleton-in-python
+#  * including @mikenerone's answer
+#   |_https://stackoverflow.com/questions/6760685/what-is-the-best-way-of-implementing-singleton-in-python/39186313#39186313
+#
+# -[ ] put it in `tractor.lowlevel._globals` ?
+#  * fits with our oustanding actor-local/global feat req?
+#   |_ https://github.com/goodboy/tractor/issues/55
+#  * how can it relate to the `Actor.lifetime_stack` that was
+#    silently patched in?
+#   |_ we could implicitly call both of these in the same
+#     spot in the runtime using the lifetime stack?
+#    - `open_singleton_cm().__exit__()`
+#    -`del_singleton()`
+#   |_ gives SC fixtue semantics to sync code oriented around
+#     sub-process lifetime?
+#  * what about with `trio.RunVar`?
+#   |_https://trio.readthedocs.io/en/stable/reference-lowlevel.html#trio.lowlevel.RunVar
+#    - which we'll need for no-GIL cpython (right?) presuming
+#      multiple `trio.run()` calls in process?
+#
+#
+# @singleton
+# async def open_service_mngr(
+#     **init_kwargs,
+# ) -> ServiceMngr:
+#     '''
+#     Note this function body is invoke IFF no existing singleton instance already
+#     exists in this proc's memory.
+
+#     '''
+#     # setup
+#     yield ServiceMngr(**init_kwargs)
+#     # teardown
+
+
+# a deletion API for explicit instance de-allocation?
+# @open_service_mngr.deleter
+# def del_service_mngr() -> None:
+#     mngr = open_service_mngr._singleton[0]
+#     open_service_mngr._singleton[0] = None
+#     del mngr
+
+
+
+# TODO: implement a singleton deco-API for wrapping the below
+# factory's impl for general actor-singleton use?
+#
+# @singleton
+# async def open_service_mngr(
+#     **init_kwargs,
+# ) -> ServiceMngr:
+#     '''
+#     Note this function body is invoke IFF no existing singleton instance already
+#     exists in this proc's memory.
+
+#     '''
+#     # setup
+#     yield ServiceMngr(**init_kwargs)
+#     # teardown
+
+
+
+# TODO: singleton factory API instead of a class API
+@acm
+async def open_service_mngr(
+    *,
+    debug_mode: bool = False,
+
+    # NOTE; since default values for keyword-args are effectively
+    # module-vars/globals as per the note from,
+    # https://docs.python.org/3/tutorial/controlflow.html#default-argument-values
+    #
+    # > "The default value is evaluated only once. This makes
+    #   a difference when the default is a mutable object such as
+    #   a list, dictionary, or instances of most classes"
+    #
+    _singleton: list[ServiceMngr|None] = [None],
+    **init_kwargs,
+
+) -> ServiceMngr:
+    '''
+    Open an actor-global "service-manager" for supervising a tree
+    of subactors and/or actor-global tasks.
+
+    The delivered `ServiceMngr` is singleton instance for each
+    actor-process, that is, allocated on first open and never
+    de-allocated unless explicitly deleted by al call to
+    `del_service_mngr()`.
+
+    '''
+    # TODO: factor this an allocation into
+    # a `._mngr.open_service_mngr()` and put in the
+    # once-n-only-once setup/`.__aenter__()` part!
+    # -[ ] how to make this only happen on the `mngr == None` case?
+    #  |_ use `.trionics.maybe_open_context()` (for generic
+    #     async-with-style-only-once of the factory impl, though
+    #     what do we do for the allocation case?
+    #    / `.maybe_open_nursery()` (since for this specific case
+    #    it's simpler?) to activate
+    async with (
+        tractor.open_nursery() as an,
+        trio.open_nursery() as tn,
+    ):
+        # impl specific obvi..
+        init_kwargs.update({
+            'an': an,
+            'tn': tn,
+        })
+
+        mngr: ServiceMngr|None
+        if (mngr := _singleton[0]) is None:
+
+            log.info('Allocating a new service mngr!')
+            mngr = _singleton[0] = ServiceMngr(**init_kwargs)
+
+            # TODO: put into `.__aenter__()` section of
+            # eventual `@singleton_acm` API wrapper.
+            #
+            # assign globally for future daemon/task creation
+            mngr.an = an
+            mngr.tn = tn
+
+        else:
+            assert (mngr.an and mngr.tn)
+            log.info(
+                'Using extant service mngr!\n\n'
+                f'{mngr!r}\n'  # it has a nice `.__repr__()` of services state
+            )
+
+        try:
+            # NOTE: this is a singleton factory impl specific detail
+            # which should be supported in the condensed
+            # `@singleton_acm` API?
+            mngr.debug_mode = debug_mode
+
+            yield mngr
+        finally:
+            # TODO: is this more clever/efficient?
+            # if 'samplerd' in mngr.service_ctxs:
+            #     await mngr.cancel_service('samplerd')
+            tn.cancel_scope.cancel()
+
+
+
+def get_service_mngr() -> ServiceMngr:
+    '''
+    Try to get the singleton service-mngr for this actor presuming it
+    has already been allocated using,
+
+    .. code:: python
+
+        async with open_<@singleton_acm(func)>() as mngr`
+            ... this block kept open ...
+
+    If not yet allocated raise a `ServiceError`.
+
+    '''
+    # https://stackoverflow.com/a/12627202
+    # https://docs.python.org/3/library/inspect.html#inspect.Signature
+    maybe_mngr: ServiceMngr|None = inspect.signature(
+        open_service_mngr
+    ).parameters['_singleton'].default[0]
+
+    if maybe_mngr is None:
+        raise RuntimeError(
+            'Someone must allocate a `ServiceMngr` using\n\n'
+            '`async with open_service_mngr()` beforehand!!\n'
+        )
+
+    return maybe_mngr
+
+
+async def _open_and_supervise_service_ctx(
+    serman: ServiceMngr,
+    name: str,
+    ctx_fn: Callable,  # TODO, type for `@tractor.context` requirement
+    portal: Portal,
+
+    allow_overruns: bool = False,
+    task_status: TaskStatus[
+        tuple[
+            trio.CancelScope,
+            Context,
+            trio.Event,
+            Any,
+        ]
+    ] = trio.TASK_STATUS_IGNORED,
+    **ctx_kwargs,
+
+) -> Any:
+    '''
+    Open a remote IPC-context defined by `ctx_fn` in the
+    (service) actor accessed via `portal` and supervise the
+    (local) parent task to termination at which point the remote
+    actor runtime is cancelled alongside it.
+
+    The main application is for allocating long-running
+    "sub-services" in a main daemon and explicitly controlling
+    their lifetimes from an actor-global singleton.
+
+    '''
+    # TODO: use the ctx._scope directly here instead?
+    # -[ ] actually what semantics do we expect for this
+    #   usage!?
+    with trio.CancelScope() as cs:
+        try:
+            async with portal.open_context(
+                ctx_fn,
+                allow_overruns=allow_overruns,
+                **ctx_kwargs,
+
+            ) as (ctx, started):
+
+                # unblock once the remote context has started
+                complete = trio.Event()
+                task_status.started((
+                    cs,
+                    ctx,
+                    complete,
+                    started,
+                ))
+                log.info(
+                    f'`pikerd` service {name} started with value {started}'
+                )
+                # wait on any context's return value
+                # and any final portal result from the
+                # sub-actor.
+                ctx_res: Any = await ctx.wait_for_result()
+
+                # NOTE: blocks indefinitely until cancelled
+                # either by error from the target context
+                # function or by being cancelled here by the
+                # surrounding cancel scope.
+                return (
+                    await portal.wait_for_result(),
+                    ctx_res,
+                )
+
+        except ContextCancelled as ctxe:
+            canceller: tuple[str, str] = ctxe.canceller
+            our_uid: tuple[str, str] = current_actor().uid
+            if (
+                canceller != portal.chan.uid
+                and
+                canceller != our_uid
+            ):
+                log.cancel(
+                    f'Actor-service `{name}` was remotely cancelled by a peer?\n'
+
+                    # TODO: this would be a good spot to use
+                    # a respawn feature Bo
+                    f'-> Keeping `pikerd` service manager alive despite this inter-peer cancel\n\n'
+
+                    f'cancellee: {portal.chan.uid}\n'
+                    f'canceller: {canceller}\n'
+                )
+            else:
+                raise
+
+        finally:
+            # NOTE: the ctx MUST be cancelled first if we
+            # don't want the above `ctx.wait_for_result()` to
+            # raise a self-ctxc. WHY, well since from the ctx's
+            # perspective the cancel request will have
+            # arrived out-out-of-band at the `Actor.cancel()`
+            # level, thus `Context.cancel_called == False`,
+            # meaning `ctx._is_self_cancelled() == False`.
+            # with trio.CancelScope(shield=True):
+            # await ctx.cancel()
+            await portal.cancel_actor()  # terminate (remote) sub-actor
+            complete.set()  # signal caller this task is done
+            serman.service_ctxs.pop(name)  # remove mngr entry
+
+
+# TODO: we need remote wrapping and a general soln:
+# - factor this into a ``tractor.highlevel`` extension # pack for the
+#   library.
+# - wrap a "remote api" wherein you can get a method proxy
+#   to the pikerd actor for starting services remotely!
+# - prolly rename this to ActorServicesNursery since it spawns
+#   new actors and supervises them to completion?
+@dataclass
+class ServiceMngr:
+    '''
+    A multi-subactor-as-service manager.
+
+    Spawn, supervise and monitor service/daemon subactors in a SC
+    process tree.
+
+    '''
+    an: ActorNursery
+    tn: trio.Nursery
+    debug_mode: bool = False # tractor sub-actor debug mode flag
+
+    service_tasks: dict[
+        str,
+        tuple[
+            trio.CancelScope,
+            trio.Event,
+        ]
+    ] = field(default_factory=dict)
+
+    service_ctxs: dict[
+        str,
+        tuple[
+            trio.CancelScope,
+            Context,
+            Portal,
+            trio.Event,
+        ]
+    ] = field(default_factory=dict)
+
+    # internal per-service task mutexs
+    _locks = defaultdict(trio.Lock)
+
+    # TODO, unify this interface with our `TaskManager` PR!
+    #
+    #
+    async def start_service_task(
+        self,
+        name: str,
+        # TODO: typevar for the return type of the target and then
+        # use it below for `ctx_res`?
+        fn: Callable,
+
+        allow_overruns: bool = False,
+        **ctx_kwargs,
+
+    ) -> tuple[
+        trio.CancelScope,
+        Any,
+        trio.Event,
+    ]:
+        async def _task_manager_start(
+            task_status: TaskStatus[
+                tuple[
+                    trio.CancelScope,
+                    trio.Event,
+                ]
+            ] = trio.TASK_STATUS_IGNORED,
+        ) -> Any:
+
+            task_cs = trio.CancelScope()
+            task_complete = trio.Event()
+
+            with task_cs as cs:
+                task_status.started((
+                    cs,
+                    task_complete,
+                ))
+                try:
+                    await fn()
+                except trio.Cancelled as taskc:
+                    log.cancel(
+                        f'Service task for `{name}` was cancelled!\n'
+                        # TODO: this would be a good spot to use
+                        # a respawn feature Bo
+                    )
+                    raise taskc
+                finally:
+                    task_complete.set()
+        (
+            cs,
+            complete,
+        ) = await self.tn.start(_task_manager_start)
+
+        # store the cancel scope and portal for later cancellation or
+        # retstart if needed.
+        self.service_tasks[name] = (
+            cs,
+            complete,
+        )
+        return (
+            cs,
+            complete,
+        )
+
+    async def cancel_service_task(
+        self,
+        name: str,
+
+    ) -> Any:
+        log.info(f'Cancelling `pikerd` service {name}')
+        cs, complete = self.service_tasks[name]
+
+        cs.cancel()
+        await complete.wait()
+        # TODO, if we use the `TaskMngr` from #346
+        # we can also get the return value from the task!
+
+        if name in self.service_tasks:
+            # TODO: custom err?
+            # raise ServiceError(
+            raise RuntimeError(
+                f'Service task {name!r} not terminated!?\n'
+            )
+
+    async def start_service_ctx(
+        self,
+        name: str,
+        portal: Portal,
+        # TODO: typevar for the return type of the target and then
+        # use it below for `ctx_res`?
+        ctx_fn: Callable,
+        **ctx_kwargs,
+
+    ) -> tuple[
+        trio.CancelScope,
+        Context,
+        Any,
+    ]:
+        '''
+        Start a remote IPC-context defined by `ctx_fn` in a background
+        task and immediately return supervision primitives to manage it:
+
+        - a `cs: CancelScope` for the newly allocated bg task
+        - the `ipc_ctx: Context` to manage the remotely scheduled
+          `trio.Task`.
+        - the `started: Any` value returned by the remote endpoint
+          task's `Context.started(<value>)` call.
+
+        The bg task supervises the ctx such that when it terminates the supporting
+        actor runtime is also cancelled, see `_open_and_supervise_service_ctx()`
+        for details.
+
+        '''
+        cs, ipc_ctx, complete, started = await self.tn.start(
+            functools.partial(
+                _open_and_supervise_service_ctx,
+                serman=self,
+                name=name,
+                ctx_fn=ctx_fn,
+                portal=portal,
+                **ctx_kwargs,
+            )
+        )
+
+        # store the cancel scope and portal for later cancellation or
+        # retstart if needed.
+        self.service_ctxs[name] = (cs, ipc_ctx, portal, complete)
+        return (
+            cs,
+            ipc_ctx,
+            started,
+        )
+
+    async def start_service(
+        self,
+        daemon_name: str,
+        ctx_ep: Callable,  # kwargs must `partial`-ed in!
+        # ^TODO, type for `@tractor.context` deco-ed funcs!
+
+        debug_mode: bool = False,
+        **start_actor_kwargs,
+
+    ) -> Context:
+        '''
+        Start new subactor and schedule a supervising "service task"
+        in it which explicitly defines the sub's lifetime.
+
+        "Service daemon subactors" are cancelled (and thus
+        terminated) using the paired `.cancel_service()`.
+
+        Effectively this API can be used to manage "service daemons"
+        spawned under a single parent actor with supervision
+        semantics equivalent to a one-cancels-one style actor-nursery
+        or "(subactor) task manager" where each subprocess's (and
+        thus its embedded actor runtime) lifetime is synced to that
+        of the remotely spawned task defined by `ctx_ep`.
+
+        The funcionality can be likened to a "daemonized" version of
+        `.hilevel.worker.run_in_actor()` but with supervision
+        controls offered by `tractor.Context` where the main/root
+        remotely scheduled `trio.Task` invoking `ctx_ep` determines
+        the underlying subactor's lifetime.
+
+        '''
+        entry: tuple|None = self.service_ctxs.get(daemon_name)
+        if entry:
+            (cs, sub_ctx, portal, complete) = entry
+            return sub_ctx
+
+        if daemon_name not in self.service_ctxs:
+            portal: Portal = await self.an.start_actor(
+                daemon_name,
+                debug_mode=(  # maybe set globally during allocate
+                    debug_mode
+                    or
+                    self.debug_mode
+                ),
+                **start_actor_kwargs,
+            )
+            ctx_kwargs: dict[str, Any] = {}
+            if isinstance(ctx_ep, functools.partial):
+                ctx_kwargs: dict[str, Any] = ctx_ep.keywords
+                ctx_ep: Callable = ctx_ep.func
+
+            (
+                cs,
+                sub_ctx,
+                started,
+            ) = await self.start_service_ctx(
+                name=daemon_name,
+                portal=portal,
+                ctx_fn=ctx_ep,
+                **ctx_kwargs,
+            )
+
+            return sub_ctx
+
+    async def cancel_service(
+        self,
+        name: str,
+
+    ) -> Any:
+        '''
+        Cancel the service task and actor for the given ``name``.
+
+        '''
+        log.info(f'Cancelling `pikerd` service {name}')
+        cs, sub_ctx, portal, complete = self.service_ctxs[name]
+
+        # cs.cancel()
+        await sub_ctx.cancel()
+        await complete.wait()
+
+        if name in self.service_ctxs:
+            # TODO: custom err?
+            # raise ServiceError(
+            raise RuntimeError(
+                f'Service actor for {name} not terminated and/or unknown?'
+            )
+
+        # assert name not in self.service_ctxs, \
+        #     f'Serice task for {name} not terminated?'

tractor/msg/_ops.py

@@ -613,10 +613,9 @@ async def drain_to_final_msg(
             #       msg: dict = await ctx._rx_chan.receive()
             #   if res_cs.cancelled_caught:
             #
-            # -[ ] make sure pause points work here for REPLing
+            # -[x] make sure pause points work here for REPLing
             #   the runtime itself; i.e. ensure there's no hangs!
-            # |_from tractor.devx.debug import pause
-            #   await pause()
+            #  |_see masked code below in .cancel_called path
 
         # NOTE: we get here if the far end was
         # `ContextCancelled` in 2 cases:
@@ -652,6 +651,10 @@ async def drain_to_final_msg(
                     f'IPC ctx cancelled externally during result drain ?\n'
                     f'{ctx}'
                 )
+                # XXX, for tracing `Cancelled`..
+                # from tractor.devx.debug import pause
+                # await pause(shield=True)
+
             # CASE 2: mask the local cancelled-error(s)
             # only when we are sure the remote error is
             # the source cause of this local task's

tractor/trionics/__init__.py

@@ -21,7 +21,6 @@ Sugary patterns for trio + tractor designs.
 from ._mngrs import (
     gather_contexts as gather_contexts,
     maybe_open_context as maybe_open_context,
-    maybe_open_nursery as maybe_open_nursery,
 )
 from ._broadcast import (
     AsyncReceiver as AsyncReceiver,
@@ -37,3 +36,6 @@ from ._beg import (
 from ._taskc import (
     maybe_raise_from_masking_exc as maybe_raise_from_masking_exc,
 )
+from ._tn import (
+    maybe_open_nursery as maybe_open_nursery,
+)

tractor/trionics/_broadcast.py

@@ -22,7 +22,7 @@ https://docs.rs/tokio/1.11.0/tokio/sync/broadcast/index.html
 from __future__ import annotations
 from abc import abstractmethod
 from collections import deque
-from contextlib import asynccontextmanager
+from contextlib import asynccontextmanager as acm
 from functools import partial
 from operator import ne
 from typing import (
@@ -398,7 +398,7 @@ class BroadcastReceiver(ReceiveChannel):
 
             return await self._receive_from_underlying(key, state)
 
-    @asynccontextmanager
+    @acm
     async def subscribe(
         self,
         raise_on_lag: bool = True,

tractor/trionics/_mngrs.py

@@ -23,7 +23,6 @@ from contextlib import (
     asynccontextmanager as acm,
 )
 import inspect
-from types import ModuleType
 from typing import (
     Any,
     AsyncContextManager,
@@ -31,24 +30,20 @@ from typing import (
     AsyncIterator,
     Callable,
     Hashable,
-    Optional,
     Sequence,
     TypeVar,
-    TYPE_CHECKING,
 )
 
 import trio
 from tractor._state import current_actor
 from tractor.log import get_logger
+from ._tn import maybe_open_nursery
 # from ._beg import collapse_eg
 # from ._taskc import (
 #     maybe_raise_from_masking_exc,
 # )
 
 
-if TYPE_CHECKING:
-    from tractor import ActorNursery
-
 
 log = get_logger(__name__)
 
@@ -56,30 +51,6 @@ log = get_logger(__name__)
 T = TypeVar("T")
 
 
-@acm
-async def maybe_open_nursery(
-    nursery: trio.Nursery|ActorNursery|None = None,
-    shield: bool = False,
-    lib: ModuleType = trio,
-
-    **kwargs,  # proxy thru
-
-) -> AsyncGenerator[trio.Nursery, Any]:
-    '''
-    Create a new nursery if None provided.
-
-    Blocks on exit as expected if no input nursery is provided.
-
-    '''
-    if nursery is not None:
-        yield nursery
-    else:
-        async with lib.open_nursery(**kwargs) as nursery:
-            if lib == trio:
-                nursery.cancel_scope.shield = shield
-            yield nursery
-
-
 async def _enter_and_wait(
     mngr: AsyncContextManager[T],
     unwrapped: dict[int, T],
@@ -204,7 +175,7 @@ class _Cache:
     a kept-alive-while-in-use async resource.
 
     '''
-    service_tn: Optional[trio.Nursery] = None
+    service_tn: trio.Nursery|None = None
     locks: dict[Hashable, trio.Lock] = {}
     users: int = 0
     values: dict[Any,  Any] = {}
@@ -213,7 +184,7 @@ class _Cache:
         tuple[trio.Nursery, trio.Event]
     ] = {}
     # nurseries: dict[int, trio.Nursery] = {}
-    no_more_users: Optional[trio.Event] = None
+    no_more_users: trio.Event|None = None
 
     @classmethod
     async def run_ctx(
@@ -223,16 +194,18 @@ class _Cache:
         task_status: trio.TaskStatus[T] = trio.TASK_STATUS_IGNORED,
 
     ) -> None:
-        async with mng as value:
-            _, no_more_users = cls.resources[ctx_key]
-            cls.values[ctx_key] = value
-            task_status.started(value)
-            try:
-                await no_more_users.wait()
-            finally:
-                # discard nursery ref so it won't be re-used (an error)?
-                value = cls.values.pop(ctx_key)
-                cls.resources.pop(ctx_key)
+        try:
+            async with mng as value:
+                _, no_more_users = cls.resources[ctx_key]
+                try:
+                    cls.values[ctx_key] = value
+                    task_status.started(value)
+                    await no_more_users.wait()
+                finally:
+                    value = cls.values.pop(ctx_key)
+        finally:
+            # discard nursery ref so it won't be re-used (an error)?
+            cls.resources.pop(ctx_key)
 
 
 @acm

tractor/trionics/_supervisor.py

@@ -0,0 +1,341 @@
+# tractor: structured concurrent "actors".
+# Copyright 2018-eternity Tyler Goodlet.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+'''
+Erlang-style (ish) "one-cancels-one" nursery, what we just call
+a "task manager".
+
+'''
+from __future__ import annotations
+from contextlib import (
+    asynccontextmanager as acm,
+    # contextmanager as cm,
+)
+from functools import partial
+from typing import (
+    Generator,
+    Any,
+)
+
+from outcome import (
+    Outcome,
+    acapture,
+)
+from msgspec import Struct
+import trio
+from trio import (
+    TaskStatus,
+    CancelScope,
+    Nursery,
+)
+from trio.lowlevel import (
+    Task,
+)
+from tractor.log import get_logger
+
+log = get_logger(__name__)
+
+
+class TaskOutcome(Struct):
+    '''
+    The outcome of a scheduled ``trio`` task which includes an interface
+    for synchronizing to the completion of the task's runtime and access
+    to the eventual boxed result/value or raised exception.
+
+    '''
+    lowlevel_task: Task
+    _exited = trio.Event()  # as per `trio.Runner.task_exited()`
+    _outcome: Outcome | None = None  # as per `outcome.Outcome`
+    _result: Any | None = None  # the eventual maybe-returned-value
+
+    @property
+    def result(self) -> Any:
+        '''
+        Either Any or None depending on whether the Outcome has compeleted.
+
+        '''
+        if self._outcome is None:
+            raise RuntimeError(
+                f'Task {self.lowlevel_task.name} is not complete.\n'
+                'First wait on `await TaskOutcome.wait_for_result()`!'
+            )
+        return self._result
+
+    def _set_outcome(
+        self,
+        outcome: Outcome,
+    ):
+        '''
+        Set the ``Outcome`` for this task.
+
+        This method should only ever be called by the task's supervising
+        nursery implemenation.
+
+        '''
+        self._outcome = outcome
+        self._result = outcome.unwrap()
+        self._exited.set()
+
+    async def wait_for_result(self) -> Any:
+        '''
+        Unwind the underlying task's ``Outcome`` by async waiting for
+        the task to first complete and then unwrap it's result-value.
+
+        '''
+        if self._exited.is_set():
+            return self._result
+
+        await self._exited.wait()
+
+        out = self._outcome
+        if out is None:
+            raise ValueError(f'{out} is not an outcome!?')
+
+        return self.result
+
+
+class TaskManagerNursery(Struct):
+    _tn: Nursery
+    _scopes: dict[
+        Task,
+        tuple[CancelScope, Outcome]
+    ] = {}
+
+    task_manager: Generator[Any, Outcome, None] | None = None
+
+    async def start_soon(
+        self,
+        async_fn,
+        *args,
+
+        name=None,
+        task_manager: Generator[Any, Outcome, None] | None = None
+
+    ) -> tuple[CancelScope, Task]:
+
+        # NOTE: internals of a nursery don't let you know what
+        # the most recently spawned task is by order.. so we'd
+        # have to either change that or do set ops.
+        # pre_start_tasks: set[Task] = n._children.copy()
+        # new_tasks = n._children - pre_start_Tasks
+        # assert len(new_tasks) == 1
+        # task = new_tasks.pop()
+
+        tn: Nursery = self._tn
+
+        sm = self.task_manager
+        # we do default behavior of a scope-per-nursery
+        # if the user did not provide a task manager.
+        if sm is None:
+            return tn.start_soon(async_fn, *args, name=None)
+
+        # new_task: Task|None = None
+        to_return: tuple[Any] | None = None
+
+        # NOTE: what do we enforce as a signature for the
+        # `@task_scope_manager` here?
+        mngr = sm(nursery=tn)
+
+        async def _start_wrapped_in_scope(
+            task_status: TaskStatus[
+                tuple[CancelScope, Task]
+            ] = trio.TASK_STATUS_IGNORED,
+
+        ) -> None:
+
+            # TODO: this was working before?! and, do we need something
+            # like it to implement `.start()`?
+            # nonlocal to_return
+
+            # execute up to the first yield
+            try:
+                to_return: tuple[Any] = next(mngr)
+            except StopIteration:
+                raise RuntimeError("task manager didn't yield") from None
+
+            # TODO: how do we support `.start()` style?
+            # - relay through whatever the
+            #   started task passes back via `.started()` ?
+            #   seems like that won't work with also returning
+            #   a "task handle"?
+            # - we were previously binding-out this `to_return` to
+            #   the parent's lexical scope, why isn't that working
+            #   now?
+            task_status.started(to_return)
+
+            # invoke underlying func now that cs is entered.
+            outcome = await acapture(async_fn, *args)
+
+            # execute from the 1st yield to return and expect
+            # generator-mngr `@task_scope_manager` thinger to
+            # terminate!
+            try:
+                mngr.send(outcome)
+
+
+                # I would presume it's better to have a handle to
+                # the `Outcome` entirely? This method sends *into*
+                # the mngr this `Outcome.value`; seems like kinda
+                # weird semantics for our purposes?
+                # outcome.send(mngr)
+
+            except StopIteration:
+                return
+            else:
+                raise RuntimeError(f"{mngr} didn't stop!")
+
+        to_return = await tn.start(_start_wrapped_in_scope)
+        assert to_return is not None
+
+        # TODO: use the fancy type-check-time type signature stuff from
+        # mypy i guess..to like, relay the type of whatever the
+        # generator yielded through? betcha that'll be un-grokable XD
+        return to_return
+
+
+# TODO: define a decorator to runtime type check that this a generator
+# with a single yield that also delivers a value (of some std type) from
+# the yield expression?
+# @trio.task_manager
+def add_task_handle_and_crash_handling(
+    nursery: Nursery,
+
+    debug_mode: bool = False,
+
+) -> Generator[
+    Any,
+    Outcome,
+    None,
+]:
+    '''
+    A customizable, user defined "task scope manager".
+
+    With this specially crafted single-yield generator function you can
+    add more granular controls around every task spawned by `trio` B)
+
+    '''
+    # if you need it you can ask trio for the task obj
+    task: Task = trio.lowlevel.current_task()
+    log.info(f'Spawning task: {task.name}')
+
+    # User defined "task handle" for more granular supervision
+    # of each spawned task as needed for their particular usage.
+    task_outcome = TaskOutcome(task)
+
+    # NOTE: if wanted the user could wrap the output task handle however
+    # they want!
+    # class TaskHandle(Struct):
+    #     task: Task
+    #     cs: CancelScope
+    #     outcome: TaskOutcome
+
+    # this yields back when the task is terminated, cancelled or returns.
+    try:
+        with CancelScope() as cs:
+
+            # the yielded value(s) here are what are returned to the
+            # nursery's `.start_soon()` caller B)
+            lowlevel_outcome: Outcome = yield (task_outcome, cs)
+            task_outcome._set_outcome(lowlevel_outcome)
+
+    # Adds "crash handling" from `pdbp` by entering
+    # a REPL on std errors.
+    except Exception as err:
+        if debug_mode:
+            log.exception(
+                f'{task.name} crashed, entering debugger!'
+            )
+            import pdbp
+            pdbp.xpm()
+
+        raise err
+
+    finally:
+        log.info(
+            f'Task exitted\n'
+            f')>\n'
+            f' |_{task}\n'
+            # ^^TODO? use sclang formatter?
+            # -[ ] .devx.pformat.nest_from_op()` yo!
+        )
+
+
+@acm
+async def open_taskman(
+    task_manager: Generator[Any, Outcome, None] | None = None,
+
+    **lowlevel_nursery_kwargs,
+):
+    async with trio.open_nursery(**lowlevel_nursery_kwargs) as nurse:
+        yield TaskManagerNursery(
+            nurse,
+            task_manager=task_manager,
+        )
+
+
+async def sleep_then_return_val(val: str):
+    await trio.sleep(0.2)
+    return val
+
+
+async def ensure_cancelled():
+    try:
+        await trio.sleep_forever()
+
+    except trio.Cancelled:
+        task = trio.lowlevel.current_task()
+        log.cancel(f'heyyo ONLY {task.name} was cancelled as expected B)')
+        assert 0
+
+    except BaseException:
+        raise RuntimeError("woa woa woa this ain't right!")
+
+
+if __name__ == '__main__':
+
+    from tractor.log import get_console_log
+    get_console_log(level='info')
+
+    async def main():
+        async with open_taskman(
+            task_manager=partial(
+                add_task_handle_and_crash_handling,
+                debug_mode=True,
+            ),
+        ) as tm:
+            for _ in range(3):
+                outcome, _ = await tm.start_soon(trio.sleep_forever)
+
+            # extra task we want to engage in debugger post mortem.
+            err_outcome, cs = await tm.start_soon(ensure_cancelled)
+
+            val: str = 'yoyoyo'
+            val_outcome, _ = await tm.start_soon(
+                sleep_then_return_val,
+                val,
+            )
+            res = await val_outcome.wait_for_result()
+            assert res == val
+            log.info(f'{res} -> GOT EXPECTED TASK VALUE')
+
+            await trio.sleep(0.6)
+            log.cancel(
+                f'Cancelling and waiting on {err_outcome.lowlevel_task} '
+                'to CRASH..'
+            )
+            cs.cancel()
+
+    trio.run(main)

tractor/trionics/_taskc.py

@@ -22,7 +22,14 @@ from __future__ import annotations
 from contextlib import (
     asynccontextmanager as acm,
 )
-from typing import TYPE_CHECKING
+import inspect
+from types import (
+    TracebackType,
+)
+from typing import (
+    Type,
+    TYPE_CHECKING,
+)
 
 import trio
 from tractor.log import get_logger
@@ -60,12 +67,71 @@ def find_masked_excs(
     return None
 
 
+_mask_cases: dict[
+    Type[Exception],  # masked exc type
+    dict[
+        int,  # inner-frame index into `inspect.getinnerframes()`
+        # `FrameInfo.function/filename: str`s to match
+        dict[str, str],
+    ],
+] = {
+    trio.WouldBlock: {
+        # `trio.Lock.acquire()` has a checkpoint inside the
+        # `WouldBlock`-no_wait path's handler..
+        -5: {  # "5th frame up" from checkpoint
+            'filename': 'trio/_sync.py',
+            'function': 'acquire',
+            # 'lineno': 605,  # matters?
+        },
+    }
+}
+
+
+def is_expected_masking_case(
+    cases: dict,
+    exc_ctx: Exception,
+    exc_match: BaseException,
+
+) -> bool|inspect.FrameInfo:
+    '''
+    Determine whether the provided masked exception is from a known
+    bug/special/unintentional-`trio`-impl case which we do not wish
+    to unmask.
+
+    Return any guilty `inspect.FrameInfo` ow `False`.
+
+    '''
+    exc_tb: TracebackType = exc_match.__traceback__
+    if cases := _mask_cases.get(type(exc_ctx)):
+        inner: list[inspect.FrameInfo] = inspect.getinnerframes(exc_tb)
+
+        # from tractor.devx.debug import mk_pdb
+        # mk_pdb().set_trace()
+        for iframe, matchon in cases.items():
+            try:
+                masker_frame: inspect.FrameInfo = inner[iframe]
+            except IndexError:
+                continue
+
+            for field, in_field in matchon.items():
+                val = getattr(
+                    masker_frame,
+                    field,
+                )
+                if in_field not in val:
+                    break
+            else:
+                return masker_frame
+
+    return False
+
+
+
 # XXX, relevant discussion @ `trio`-core,
 # https://github.com/python-trio/trio/issues/455
 #
 @acm
 async def maybe_raise_from_masking_exc(
-    tn: trio.Nursery|None = None,
     unmask_from: (
         BaseException|
         tuple[BaseException]
@@ -74,18 +140,30 @@ async def maybe_raise_from_masking_exc(
     raise_unmasked: bool = True,
     extra_note: str = (
         'This can occurr when,\n'
-        ' - a `trio.Nursery` scope embeds a `finally:`-block '
-        'which executes a checkpoint!'
+        '\n'
+        ' - a `trio.Nursery/CancelScope` embeds a `finally/except:`-block '
+        'which execs an un-shielded checkpoint!'
         #
         # ^TODO? other cases?
     ),
 
-    always_warn_on: tuple[BaseException] = (
+    always_warn_on: tuple[Type[BaseException]] = (
         trio.Cancelled,
     ),
+
+    # don't ever unmask or warn on any masking pair,
+    # {<masked-excT-key> -> <masking-excT-value>}
+    never_warn_on: dict[
+        Type[BaseException],
+        Type[BaseException],
+    ] = {
+        KeyboardInterrupt: trio.Cancelled,
+        trio.Cancelled: trio.Cancelled,
+    },
     # ^XXX, special case(s) where we warn-log bc likely
     # there will be no operational diff since the exc
     # is always expected to be consumed.
+
 ) -> BoxedMaybeException:
     '''
     Maybe un-mask and re-raise exception(s) suppressed by a known
@@ -104,81 +182,112 @@ async def maybe_raise_from_masking_exc(
         individual sub-excs but maintain the eg-parent's form right?
 
     '''
+    if not isinstance(unmask_from, tuple):
+        raise ValueError(
+            f'Invalid unmask_from = {unmask_from!r}\n'
+            f'Must be a `tuple[Type[BaseException]]`.\n'
+        )
+
     from tractor.devx.debug import (
         BoxedMaybeException,
-        pause,
     )
     boxed_maybe_exc = BoxedMaybeException(
         raise_on_exit=raise_unmasked,
     )
     matching: list[BaseException]|None = None
-    maybe_eg: ExceptionGroup|None
-
-    if tn:
-        try:  # handle egs
-            yield boxed_maybe_exc
-            return
-        except* unmask_from as _maybe_eg:
-            maybe_eg = _maybe_eg
+    try:
+        yield boxed_maybe_exc
+        return
+    except BaseException as _bexc:
+        bexc = _bexc
+        if isinstance(bexc, BaseExceptionGroup):
             matches: ExceptionGroup
-            matches, _ = maybe_eg.split(
-                unmask_from
-            )
-            if not matches:
-                raise
+            matches, _ = bexc.split(unmask_from)
+            if matches:
+                matching = matches.exceptions
 
-            matching: list[BaseException] = matches.exceptions
-    else:
-        try:  # handle non-egs
-            yield boxed_maybe_exc
-            return
-        except unmask_from as _maybe_exc:
-            maybe_exc = _maybe_exc
-            matching: list[BaseException] = [
-                maybe_exc
-            ]
-
-        # XXX, only unmask-ed for debuggin!
-        # TODO, remove eventually..
-        except BaseException as _berr:
-            berr = _berr
-            await pause(shield=True)
-            raise berr
+        elif (
+            unmask_from
+            and
+            type(bexc) in unmask_from
+        ):
+            matching = [bexc]
 
     if matching is None:
         raise
 
     masked: list[tuple[BaseException, BaseException]] = []
     for exc_match in matching:
-
         if exc_ctx := find_masked_excs(
             maybe_masker=exc_match,
-            unmask_from={unmask_from},
+            unmask_from=set(unmask_from),
         ):
-            masked.append((exc_ctx, exc_match))
+            masked.append((
+                exc_ctx,
+                exc_match,
+            ))
             boxed_maybe_exc.value = exc_match
             note: str = (
                 f'\n'
-                f'^^WARNING^^ the above {exc_ctx!r} was masked by a {unmask_from!r}\n'
+                f'^^WARNING^^\n'
+                f'the above {type(exc_ctx)!r} was masked by a {type(exc_match)!r}\n'
             )
             if extra_note:
                 note += (
                     f'\n'
                     f'{extra_note}\n'
                 )
-            exc_ctx.add_note(note)
 
-            if type(exc_match) in always_warn_on:
+            do_warn: bool = (
+                never_warn_on.get(
+                    type(exc_ctx)  # masking type
+                )
+                is not
+                type(exc_match)  # masked type
+            )
+
+            if do_warn:
+                exc_ctx.add_note(note)
+
+            if (
+                do_warn
+                and
+                type(exc_match) in always_warn_on
+            ):
                 log.warning(note)
 
-            # await tractor.pause(shield=True)
-            if raise_unmasked:
-
+            if (
+                do_warn
+                and
+                raise_unmasked
+            ):
                 if len(masked) < 2:
+                    # don't unmask already known "special" cases..
+                    if (
+                        _mask_cases
+                        and
+                        (cases := _mask_cases.get(type(exc_ctx)))
+                        and
+                        (masker_frame := is_expected_masking_case(
+                            cases,
+                            exc_ctx,
+                            exc_match,
+                        ))
+                    ):
+                        log.warning(
+                            f'Ignoring already-known, non-ideal-but-valid '
+                            f'masker code @\n'
+                            f'{masker_frame}\n'
+                            f'\n'
+                            f'NOT raising {exc_ctx} from masker {exc_match!r}\n'
+                        )
+                        raise exc_match
+
                     raise exc_ctx from exc_match
-                else:
-                    # ?TODO, see above but, possibly unmasking sub-exc
-                    # entries if there are > 1
-                    await pause(shield=True)
+
+                # ??TODO, see above but, possibly unmasking sub-exc
+                # entries if there are > 1
+                # else:
+                #     await pause(shield=True)
     else:
         raise

tractor/trionics/_tn.py

@@ -0,0 +1,94 @@
+# tractor: structured concurrent "actors".
+# Copyright 2018-eternity Tyler Goodlet.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+'''
+`trio.Nursery` wrappers which we short-hand refer to as
+`tn`: "task nursery".
+
+(whereas we refer to `tractor.ActorNursery` as the short-hand `an`)
+
+'''
+from __future__ import annotations
+from contextlib import (
+    asynccontextmanager as acm,
+)
+from types import ModuleType
+from typing import (
+    Any,
+    AsyncGenerator,
+    TYPE_CHECKING,
+)
+
+import trio
+from tractor.log import get_logger
+
+# from ._beg import (
+#     collapse_eg,
+# )
+
+if TYPE_CHECKING:
+    from tractor import ActorNursery
+
+log = get_logger(__name__)
+
+
+# ??TODO? is this even a good idea??
+# it's an extra LoC to stack `collapse_eg()` vs.
+# a new/foreign/bad-std-named very thing wrapper..?
+# -[ ] is there a better/simpler name?
+# @acm
+# async def open_loose_tn() -> trio.Nursery:
+#     '''
+#     Implements the equivalent of the old style loose eg raising
+#     task-nursery from `trio<=0.25.0` ,
+
+#     .. code-block:: python
+
+#         async with trio.open_nursery(
+#             strict_exception_groups=False,
+#         ) as tn:
+#             ...
+
+#     '''
+#     async with (
+#         collapse_eg(),
+#         trio.open_nursery() as tn,
+#     ):
+#         yield tn
+
+
+@acm
+async def maybe_open_nursery(
+    nursery: trio.Nursery|ActorNursery|None = None,
+    shield: bool = False,
+    lib: ModuleType = trio,
+    loose: bool = False,
+
+    **kwargs,  # proxy thru
+
+) -> AsyncGenerator[trio.Nursery, Any]:
+    '''
+    Create a new nursery if None provided.
+
+    Blocks on exit as expected if no input nursery is provided.
+
+    '''
+    if nursery is not None:
+        yield nursery
+    else:
+        async with lib.open_nursery(**kwargs) as tn:
+            tn.cancel_scope.shield = shield
+            yield tn