Add ctx-ep suite for `trio`'s *finally-footgun*
Deats are documented within, but basically a subtlety we already track with `trio`'s masking of excs by a checkpoint-in-`finally` can cause compounded issues with our `@context` endpoints, mostly in terms of remote error and cancel-ack relay semantics.moar_eg_smoothing
Tyler Goodlet
parent
6c46882545
commit
a21d9b1e33
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'''
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Special case testing for issues not (dis)covered in the primary
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`Context` related functional/scenario suites.
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**NOTE: this mod is a WIP** space for handling
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odd/rare/undiscovered/not-yet-revealed faults which either
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loudly (ideal case) breakl our supervision protocol
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or (worst case) result in distributed sys hangs.
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Suites here further try to clarify (if [partially] ill-defined) and
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verify our edge case semantics for inter-actor-relayed-exceptions
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including,
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- lowlevel: what remote obj-data is interchanged for IPC and what is
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native-obj form is expected from unpacking in the the new
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mem-domain.
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- which kinds of `RemoteActorError` (and its derivs) are expected by which
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(types of) peers (parent, child, sibling, etc) with what
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particular meta-data set such as,
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- `.src_uid`: the original (maybe) peer who raised.
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- `.relay_uid`: the next-hop-peer who sent it.
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- `.relay_path`: the sequence of peer actor hops.
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- `.is_inception`: a predicate that denotes multi-hop remote errors.
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- when should `ExceptionGroup`s be relayed from a particular
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remote endpoint, they should never be caused by implicit `._rpc`
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nursery machinery!
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- various special `trio` edge cases around its cancellation semantics
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and how we (currently) leverage `trio.Cancelled` as a signal for
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whether a `Context` task should raise `ContextCancelled` (ctx).
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'''
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# from contextlib import (
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# asynccontextmanager as acm,
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# )
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import pytest
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import trio
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import tractor
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from tractor import ( # typing
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ActorNursery,
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Portal,
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Context,
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ContextCancelled,
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)
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# from tractor._testing import (
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# tractor_test,
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# expect_ctxc,
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# )
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@tractor.context
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async def sleep_n_chkpt_in_finally(
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ctx: Context,
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sleep_n_raise: bool,
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chld_raise_delay: float,
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chld_finally_delay: float,
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rent_cancels: bool,
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rent_ctxc_delay: float,
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gto_task: bool = False,
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tn_cancels: bool = False,
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expect_exc: str|None = None,
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) -> None:
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'''
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Sync, open a tn, then wait for cancel, run a chkpt inside
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the user's `finally:` teardown.
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This covers a footgun case that `trio` core doesn't seem to care about
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wherein an exc can be masked by a `trio.Cancelled` raised inside a tn emedded
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`finally:`.
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Also see `test_trioisms::test_acm_embedded_nursery_propagates_enter_err`
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for the down and gritty details.
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Since a `@context` endpoint fn can also contain code like this,
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**and** bc we currently have no easy way other then
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`trio.Cancelled` to signal cancellation on each side of an IPC `Context`,
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the footgun issue can compound itself as demonstrated in this suite..
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Here are some edge cases codified with "sclang" syntax.
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Note that the parent/child relationship is just a pragmatic
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choice, these cases can occurr regardless of the supervision
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hiearchy,
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- rent c)=> chld.raises-then-taskc-in-finally
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|_ chld's body raises an `exc: BaseException`.
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_ in its `finally:` block it runs a chkpoint
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which raises a taskc (`trio.Cancelled`) which
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masks `exc` instead raising taskc up to the first tn.
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_ the embedded/chld tn captures the masking taskc and then
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raises it up to the ._rpc-ep-tn instead of `exc`.
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_ the rent thinks the child ctxc-ed instead of errored..
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'''
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await ctx.started()
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if expect_exc:
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expect_exc: BaseException = tractor._exceptions.get_err_type(
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type_name=expect_exc,
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)
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berr: BaseException|None = None
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async with (
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tractor.trionics.collapse_eg(
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# raise_from_src=True, # to show orig eg
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),
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trio.open_nursery() as tn
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):
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if gto_task:
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tn.start_soon(trio.sleep_forever())
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try:
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if not sleep_n_raise:
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await trio.sleep_forever()
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elif sleep_n_raise:
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# XXX this sleep is less then the sleep the parent
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# does before calling `ctx.cancel()`
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await trio.sleep(chld_raise_delay)
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# XXX this will be masked by a taskc raised in
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# the `finally:` if this fn doesn't terminate
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# before any ctxc-req arrives AND a checkpoint is hit
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# in that `finally:`.
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raise RuntimeError('my app krurshed..')
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except BaseException as _berr:
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berr = _berr
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# TODO: it'd sure be nice to be able to inject our own
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# `ContextCancelled` here instead of of `trio.Cancelled`
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# so that our runtime can expect it and this "user code"
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# would be able to tell the diff between a generic trio
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# cancel and a tractor runtime-IPC cancel.
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if expect_exc:
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if not isinstance(
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berr,
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expect_exc,
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):
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raise ValueError(
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f'Unexpected exc type ??\n'
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f'{berr!r}\n'
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f'\n'
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f'Expected a {expect_exc!r}\n'
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)
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raise berr
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# simulate what user code might try even though
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# it's a known boo-boo..
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finally:
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# maybe wait for rent ctxc to arrive
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with trio.CancelScope(shield=True):
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await trio.sleep(chld_finally_delay)
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if tn_cancels:
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tn.cancel_scope.cancel()
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# !!XXX this will raise `trio.Cancelled` which
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# will mask the RTE from above!!!
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#
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# YES, it's the same case as our extant
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# `test_trioisms::test_acm_embedded_nursery_propagates_enter_err`
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try:
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await trio.lowlevel.checkpoint()
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except trio.Cancelled as taskc:
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if (scope_err := taskc.__context__):
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print(
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f'XXX MASKED REMOTE ERROR XXX\n'
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f'ENDPOINT exception -> {scope_err!r}\n'
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f'will be masked by -> {taskc!r}\n'
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)
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# await tractor.pause(shield=True)
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raise taskc
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@pytest.mark.parametrize(
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'chld_callspec',
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[
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dict(
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sleep_n_raise=None,
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chld_raise_delay=0.1,
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chld_finally_delay=0.1,
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expect_exc='Cancelled',
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rent_cancels=True,
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rent_ctxc_delay=0.1,
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tn_cancels=True,
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),
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dict(
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sleep_n_raise='RuntimeError',
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chld_raise_delay=0.1,
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chld_finally_delay=1,
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expect_exc='RuntimeError',
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rent_cancels=False,
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rent_ctxc_delay=0.1,
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tn_cancels=False,
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),
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],
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ids=lambda item: f'chld_callspec={item!r}'
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)
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def test_masked_taskc_with_taskc_still_is_contx(
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debug_mode: bool,
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chld_callspec: dict,
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tpt_proto: str,
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):
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expect_exc_str: str|None = chld_callspec['sleep_n_raise']
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rent_ctxc_delay: float|None = chld_callspec['rent_ctxc_delay']
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async def main():
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an: ActorNursery
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async with tractor.open_nursery(
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debug_mode=debug_mode,
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enable_transports=[tpt_proto],
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) as an:
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ptl: Portal = await an.start_actor(
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'cancellee',
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enable_modules=[__name__],
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)
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ctx: Context
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async with (
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ptl.open_context(
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sleep_n_chkpt_in_finally,
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**chld_callspec,
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) as (ctx, sent),
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):
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assert not sent
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await trio.sleep(rent_ctxc_delay)
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await ctx.cancel()
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# recv error or result from chld
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ctxc: ContextCancelled = await ctx.wait_for_result()
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assert (
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ctxc is ctx.outcome
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and
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isinstance(ctxc, ContextCancelled)
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)
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# always graceful terminate the sub in non-error cases
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await an.cancel()
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if expect_exc_str:
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expect_exc: BaseException = tractor._exceptions.get_err_type(
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type_name=expect_exc_str,
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)
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with pytest.raises(
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expected_exception=tractor.RemoteActorError,
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) as excinfo:
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trio.run(main)
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rae = excinfo.value
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assert expect_exc == rae.boxed_type
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else:
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trio.run(main)
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Loading…
Reference in New Issue