Wrap `send_chan_aclose_masks_beg.py` as test suite

Call it `test_trioisms::test_unmask_aclose_as_checkpoint_on_aexit` and
parametrize all script-mod`.main()` toggles including `.xfails()` for
the `raise_unmasked=False` cases.

examples/trio/send_chan_aclose_masks_beg.py

@@ -9,8 +9,10 @@ import tractor
 import trio
 
 
-log = tractor.log.get_logger(__name__)
+log = tractor.log.get_logger(
-tractor.log.get_console_log('info')
+    name=__name__
+)
+
 
 @cm
 def teardown_on_exc(
@@ -54,6 +56,7 @@ def teardown_on_exc(
 async def finite_stream_to_rent(
     tx: trio.abc.SendChannel,
     child_errors_mid_stream: bool,
+    raise_unmasked: bool,
 
     task_status: trio.TaskStatus[
         trio.CancelScope,
@@ -68,20 +71,41 @@ async def finite_stream_to_rent(
         # inside the child  task!
         #
         # TODO, uncomment next LoC to see the supprsessed beg[RTE]!
-        # tractor.trionics.maybe_raise_from_masking_exc(),
+        tractor.trionics.maybe_raise_from_masking_exc(
+            raise_unmasked=raise_unmasked,
+        ),
 
         tx as tx,  # .aclose() is the guilty masker chkpt!
-        trio.open_nursery() as _tn,
+
+        # 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.
-        task_status.started(_tn.cancel_scope)
+        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.info(
+                log.debug(
                     f'Child tx {i!r}\n'
                 )
                 if (
@@ -107,23 +131,31 @@ async def main(
     #   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.info(
+            log.debug(
                 f'Rent rx {msg!r}\n'
             )
 
@@ -139,7 +171,25 @@ async def main(
                 tn.cancel_scope.cancel()
 
 
+# XXX, manual test as script
 if __name__ == '__main__':
-
+    tractor.log.get_console_log(level='info')
     for case in [True, False]:
-        trio.run(main, case)
+        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_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
+    Demo how a masking `trio.Cancelled` could be handled by unmasking
-    `.__context__` field when a user (by accident) re-raises from a `finally:`.
+    from the `.__context__` field when a user (by accident) re-raises
+    from a `finally:`.
 
     '''
     import tractor
@@ -158,13 +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
+    Demo how a using an `async with sndchan` inside
-    will break a strict-eg-tn's multi-cancelled absorption..
+    a `.trionics.gather_contexts()` task will break a strict-eg-tn's
+    multi-cancelled absorption..
 
     '''
     from tractor import (
@@ -190,7 +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
@@ -211,3 +218,50 @@ 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,
+        ))