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import pytest
import gc
from snakeoil.caching import WeakInstMeta
class weak_slotted(metaclass=WeakInstMeta):
__inst_caching__ = True
__slots__ = ('one',)
class weak_inst(metaclass=WeakInstMeta):
__inst_caching__ = True
counter = 0
def __new__(cls, *args, **kwargs):
cls.counter += 1
return object.__new__(cls)
def __init__(self, *args, **kwargs):
pass
@classmethod
def reset(cls):
cls.counter = 0
class automatic_disabled_weak_inst(weak_inst):
pass
class explicit_disabled_weak_inst(weak_inst):
__inst_caching__ = False
class reenabled_weak_inst(automatic_disabled_weak_inst):
__inst_caching__ = True
class TestWeakInstMeta:
def test_reuse(self, kls=weak_inst):
kls.reset()
o = kls()
assert o is kls()
assert kls.counter == 1
del o
gc.collect()
kls()
assert kls.counter == 2
def test_disabling_inst(self):
weak_inst.reset()
for x in (1, 2):
o = weak_inst(disable_inst_caching=True)
assert weak_inst.counter is x
del o
gc.collect()
o = weak_inst()
assert o is not weak_inst(disable_inst_caching=True)
def test_class_disabling(self):
automatic_disabled_weak_inst.reset()
assert automatic_disabled_weak_inst() is not automatic_disabled_weak_inst()
assert explicit_disabled_weak_inst() is not explicit_disabled_weak_inst()
def test_reenabled(self):
self.test_reuse(reenabled_weak_inst)
# Read this before doing anything with the warnings-related
# tests unless you really enjoy debugging Heisenbugs.
#
# The warnings module is optimized for the common case of
# warnings that should be ignored: it stores a "key"
# consisting of the type of warning, the warning message and
# the module it originates from in a dict (cleverly hidden
# away in the globals() of the frame calling warn()) if a
# warning should be ignored, and then immediately ignores
# warnings matching that key, *without* looking at the current
# filters list.
#
# This means that if our test(s) with warnings ignored run
# before tests with warnings turned into exceptions (test
# order is random, enter Heisenbugs) and both tests involve
# the same exception message they will screw up the tests.
#
# To make matters more interesting the warning message we deal
# with here is not constant. Specifically it contains the
# repr() of an argument tuple, containing a class instance,
# which means the message will contain the address that object
# is stored at!
#
# This exposed itself as crazy test failures where running
# from .py fails and from .pyc works (perhaps related to the
# warnings module taking a different codepath for this) and
# creating objects or setting pdb breakpoints before that
# failure caused the test to pass again.
#
# What all this means: Be 100% positively absolutely sure
# test_uncachable and test_uncachable_warnings do not see the
# same warning message ever. We do that by making sure their
# warning messages contain a different classname
# (RaisingHashFor...).
# UserWarning is ignored and everything other warning is an error.
@pytest.mark.filterwarnings('ignore::UserWarning')
@pytest.mark.filterwarnings('error')
def test_uncachable(self):
weak_inst.reset()
# This name is *important*, see above.
class RaisingHashForTestUncachable:
def __init__(self, error):
self.error = error
def __hash__(self):
raise self.error
assert weak_inst([]) is not weak_inst([])
assert weak_inst.counter == 2
for x in (TypeError, NotImplementedError):
assert weak_inst(RaisingHashForTestUncachable(x)) is not \
weak_inst(RaisingHashForTestUncachable(x))
@pytest.mark.filterwarnings('error::UserWarning')
def test_uncachable_warning_msg(self):
# This name is *important*, see above.
class RaisingHashForTestUncachableWarnings:
def __init__(self, error):
self.error = error
def __hash__(self):
raise self.error
for x in (TypeError, NotImplementedError):
with pytest.raises(UserWarning):
weak_inst(RaisingHashForTestUncachableWarnings(x))
def test_hash_collision(self):
class BrokenHash:
def __hash__(self):
return 1
assert weak_inst(BrokenHash()) is not weak_inst(BrokenHash())
def test_weak_slot(self):
weak_slotted()
def test_keyword_args(self):
o = weak_inst(argument=1)
assert o is weak_inst(argument=1)
assert o is not weak_inst(argument=2)
def test_existing_weakref_slot(self):
# The actual test is that the class definition works.
class ExistingWeakrefSlot:
__inst_caching__ = True
__slots__ = ('one', '__weakref__')
assert ExistingWeakrefSlot()
def test_weakref(self):
weak_inst.reset()
unique = object()
o = weak_inst(unique)
# make sure it's only strong ref-ed
assert weak_inst.counter == 1
_myid = id(o)
del o
gc.collect()
o = weak_inst(unique)
assert weak_inst.counter == 2
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