Investigate replacing addfinalizer with ExitStack

[graingert]

addfinalizer can be implemented in terms of adding a callback to a stack

it would be interesting if there was a per usage scope fixture for eexit stacks,

then each fixture could get a very own exit stack in a well expressed manner (and if each fixture had one, it wouldnt be as bad to expose it)

Originally posted by @RonnyPfannschmidt in #5589 (comment)

[graingert]

note: ExitStack exposes pop_all any implementation would have to remove such access

[graingert]

@RonnyPfannschmidt how about exposing request.exit_stack as an instance of:

class RequestExitStack(contextlib.ExitStack):
    def pop_all(self):
        raise NotImplimentedError

[graingert]

However this is only if there's a usecase for addfinalizer that can't be replaced with a yield fixture using ExitStack

[RonnyPfannschmidt]

@graingert i'd like to defer exporting exit stacks until they are a "per fixture request" style/type of fixture

if each fixture request has a own exit stack, then its fine if a fixture pops all its things

[nicoddemus]

@RonnyPfannschmidt did you ever get a chance to read #4871? It is related to how finalizers are handled.

[RonnyPfannschmidt]

no, will do now