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import gc
import sys
from collections.abc import Callable
from typing import TYPE_CHECKING, Any, Protocol, TypedDict, TypeVar
import pytest
from propcache.api import under_cached_property
IS_PYPY = hasattr(sys, "pypy_version_info")
if sys.version_info >= (3, 11):
from typing import assert_type
_T_co = TypeVar("_T_co", covariant=True)
class APIProtocol(Protocol):
def under_cached_property(
self, func: Callable[[Any], _T_co]
) -> under_cached_property[_T_co]: ...
def test_under_cached_property(propcache_module: APIProtocol) -> None:
class A:
def __init__(self) -> None:
self._cache: dict[str, int] = {}
@propcache_module.under_cached_property
def prop(self) -> int:
return 1
@propcache_module.under_cached_property
def prop2(self) -> str:
return "foo"
a = A()
if sys.version_info >= (3, 11):
assert_type(a.prop, int)
assert a.prop == 1
if sys.version_info >= (3, 11):
assert_type(a.prop2, str)
assert a.prop2 == "foo"
def test_under_cached_property_typeddict(propcache_module: APIProtocol) -> None:
"""Test static typing passes with TypedDict."""
class _Cache(TypedDict, total=False):
prop: int
prop2: str
class A:
def __init__(self) -> None:
self._cache: _Cache = {}
@propcache_module.under_cached_property
def prop(self) -> int:
return 1
@propcache_module.under_cached_property
def prop2(self) -> str:
return "foo"
a = A()
if sys.version_info >= (3, 11):
assert_type(a.prop, int)
assert a.prop == 1
if sys.version_info >= (3, 11):
assert_type(a.prop2, str)
assert a.prop2 == "foo"
def test_under_cached_property_assignment(propcache_module: APIProtocol) -> None:
class A:
def __init__(self) -> None:
self._cache: dict[str, Any] = {}
@propcache_module.under_cached_property
def prop(self) -> None:
"""Mock property."""
a = A()
with pytest.raises(AttributeError):
a.prop = 123 # type: ignore[assignment]
def test_under_cached_property_without_cache(propcache_module: APIProtocol) -> None:
class A:
def __init__(self) -> None:
"""Init."""
self._cache: dict[str, int] = {}
@propcache_module.under_cached_property
def prop(self) -> None:
"""Mock property."""
a = A()
with pytest.raises(AttributeError):
a.prop = 123 # type: ignore[assignment]
def test_under_cached_property_check_without_cache(
propcache_module: APIProtocol,
) -> None:
class A:
def __init__(self) -> None:
"""Init."""
# Note that self._cache is intentionally missing
# here to verify AttributeError
@propcache_module.under_cached_property
def prop(self) -> None:
"""Mock property."""
a = A()
with pytest.raises(AttributeError):
_ = a.prop # type: ignore[call-overload]
def test_under_cached_property_caching(propcache_module: APIProtocol) -> None:
class A:
def __init__(self) -> None:
self._cache: dict[str, int] = {}
@propcache_module.under_cached_property
def prop(self) -> int:
"""Docstring."""
return 1
a = A()
assert a.prop == 1
def test_under_cached_property_class_docstring(propcache_module: APIProtocol) -> None:
class A:
def __init__(self) -> None:
"""Init."""
@propcache_module.under_cached_property
def prop(self) -> None:
"""Docstring."""
if TYPE_CHECKING:
# At type checking, the fixture doesn't represent the real module, so
# we use the global-level imported module to verify the isinstance() check here
# matches the behaviour users would see in real code.
assert isinstance(A.prop, under_cached_property)
else:
assert isinstance(A.prop, propcache_module.under_cached_property)
assert "Docstring." == A.prop.__doc__
def test_ensured_wrapped_function_is_accessible(propcache_module: APIProtocol) -> None:
"""Test that the wrapped function can be accessed from python."""
class A:
def __init__(self) -> None:
"""Init."""
self._cache: dict[str, int] = {}
@propcache_module.under_cached_property
def prop(self) -> int:
"""Docstring."""
return 1
a = A()
assert A.prop.wrapped(a) == 1
@pytest.mark.c_extension
@pytest.mark.skipif(IS_PYPY, reason="PyPy has no C extension")
def test_under_cached_property_no_refcount_leak(propcache_module: APIProtocol) -> None:
"""Test that under_cached_property does not leak references."""
class UnderCachedPropertySentinel:
"""A unique object we can track."""
def count_sentinels() -> int:
"""Count the number of UnderCachedPropertySentinel instances in gc."""
gc.collect()
return sum(
1
for obj in gc.get_objects()
if isinstance(obj, UnderCachedPropertySentinel)
)
class A:
def __init__(self) -> None:
"""Init."""
self._cache: dict[str, Any] = {}
@propcache_module.under_cached_property
def prop(self) -> UnderCachedPropertySentinel:
"""Return a sentinel object."""
return UnderCachedPropertySentinel()
initial_sentinel_count = count_sentinels()
a = A()
# First access - creates and caches the object
result = a.prop
# sys.getrefcount returns 1 higher than actual (the temp ref from the call)
# After first access: result owns 1, _cache owns 1, getrefcount call owns 1 = 3
initial_refcount = sys.getrefcount(result)
# Should have exactly 1 Sentinel instance now
assert count_sentinels() == initial_sentinel_count + 1
# Second access - should return the cached object without creating new refs
result2 = a.prop
assert result is result2
# After second access: result owns 1, result2 owns 1, _cache owns 1, getrefcount call owns 1 = 4
# Only result2 should add 1
second_refcount = sys.getrefcount(result)
assert second_refcount == initial_refcount + 1
# Still should have exactly 1 Sentinel instance
assert count_sentinels() == initial_sentinel_count + 1
# Third access
result3 = a.prop
assert result is result3
# result2 and result3 each add 1
third_refcount = sys.getrefcount(result)
assert third_refcount == initial_refcount + 2
# Clean up local refs - should be back to just result and _cache
del result2
del result3
after_cleanup_refcount = sys.getrefcount(result)
assert after_cleanup_refcount == initial_refcount
# Clear the cache and verify no leak when re-fetching
# After clearing: only result owns it
del a._cache["prop"]
cleared_refcount = sys.getrefcount(result)
assert cleared_refcount == initial_refcount - 1 # No longer in _cache
# Re-fetch - this should create a new object, not affect old one
result4 = a.prop
assert result4 is not result # Should be a new object
refetch_refcount = sys.getrefcount(result)
assert refetch_refcount == cleared_refcount # Original object refcount unchanged
# Now we should have 2 Sentinel instances:
# - original in `result`
# - new one in `result4`
assert count_sentinels() == initial_sentinel_count + 2
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