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decorator: Strengthen types of signature-preserving decorators.

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Signed-off-by: Anders Kaseorg <anders@zulip.com>
This commit is contained in:
Anders Kaseorg
2020-06-23 16:52:37 -07:00
parent a7bac82f2e
commit e582bbea4a
4 changed files with 37 additions and 33 deletions
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19
zerver/lib/cache.py
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@@ -20,6 +20,7 @@ from typing import (
Sequence,
Tuple,
TypeVar,
cast,
)
from django.conf import settings
@@ -39,7 +40,7 @@ if TYPE_CHECKING:
MEMCACHED_MAX_KEY_LENGTH = 250
ReturnT = TypeVar('ReturnT') # Useful for matching return types via Callable[..., ReturnT]
FuncT = TypeVar('FuncT', bound=Callable[..., object])
logger = logging.getLogger()
@@ -127,15 +128,15 @@ def get_cache_backend(cache_name: Optional[str]) -> BaseCache:
def get_cache_with_key(
keyfunc: Callable[..., str],
cache_name: Optional[str]=None,
) -> Callable[[Callable[..., ReturnT]], Callable[..., ReturnT]]:
) -> Callable[[FuncT], FuncT]:
"""
The main goal of this function getting value from the cache like in the "cache_with_key".
A cache value can contain any data including the "None", so
here used exception for case if value isn't found in the cache.
"""
def decorator(func: Callable[..., ReturnT]) -> (Callable[..., ReturnT]):
def decorator(func: FuncT) -> FuncT:
@wraps(func)
def func_with_caching(*args: Any, **kwargs: Any) -> Callable[..., ReturnT]:
def func_with_caching(*args: object, **kwargs: object) -> object:
key = keyfunc(*args, **kwargs)
try:
val = cache_get(key, cache_name=cache_name)
@@ -148,14 +149,14 @@ def get_cache_with_key(
return val[0]
raise NotFoundInCache()
return func_with_caching
return cast(FuncT, func_with_caching) # https://github.com/python/mypy/issues/1927
return decorator
def cache_with_key(
keyfunc: Callable[..., str], cache_name: Optional[str]=None,
timeout: Optional[int]=None, with_statsd_key: Optional[str]=None,
) -> Callable[[Callable[..., ReturnT]], Callable[..., ReturnT]]:
) -> Callable[[FuncT], FuncT]:
"""Decorator which applies Django caching to a function.
Decorator argument is a function which computes a cache key
@@ -163,9 +164,9 @@ def cache_with_key(
for avoiding collisions with other uses of this decorator or
other uses of caching."""
def decorator(func: Callable[..., ReturnT]) -> Callable[..., ReturnT]:
def decorator(func: FuncT) -> FuncT:
@wraps(func)
def func_with_caching(*args: Any, **kwargs: Any) -> ReturnT:
def func_with_caching(*args: object, **kwargs: object) -> object:
key = keyfunc(*args, **kwargs)
try:
@@ -198,7 +199,7 @@ def cache_with_key(
return val
return func_with_caching
return cast(FuncT, func_with_caching) # https://github.com/python/mypy/issues/1927
return decorator