Use ParamSpec for wrapped signatures

[Dreamsorcerer]

Fixes #504.

There are still a couple of issues with this.

1. Typing doesn't seem to work correctly with instance methods. Not sure how to fix this. Seems to be caused by this code:

   async-lru/async_lru/__init__.py

   Lines 227 to 233 in 0f20348

   	def __get__(
   	self, instance: _T, owner: Optional[Type[_T]]
   	) -> Union[Self, "_LRUCacheWrapperInstanceMethod[_P, _R, _T]"]:
   	if owner is None:
   	return self
   	else:
   	return _LRUCacheWrapperInstanceMethod(self, instance)

2. partial() use will cause new type errors. We can either wait until partial() is properly supported by typedshed/mypy (functools.partial should use PEP612 ParamSpec (depends on #8708) python/typeshed#8703 / functools.partial support python/mypy#1484), or we could expose a TypeAlias of _LRUCacheWrapper so it can be used in type annotations.
3. There also seems to be an issue with pypy, possibly a bug in pypy, but needs further investigation.
4. partial() doesn't pass the actual types through. We can merge without this though. (ParamSpec seems to get lost with partial() python/mypy#18589)
5. partialmethod() use will cause new type errors. It's uncommon enough that we can probably merge without this. (functools.partialmethod not supported properly? python/mypy#8619)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.92%. Comparing base (f60bf71) to head (0e56d88).
Report is 52 commits behind head on master.

❗ Current head 0e56d88 differs from pull request most recent head c8156f9

Please upload reports for the commit c8156f9 to get more accurate results.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #508      +/-   ##
==========================================
+ Coverage   96.88%   96.92%   +0.03%     
==========================================
  Files          12       12              
  Lines         770      780      +10     
  Branches       91       93       +2     
==========================================
+ Hits          746      756      +10     
  Misses         22       22              
  Partials        2        2              

Flag	Coverage Δ
unit	96.53% <91.66%> (-0.22%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[asvetlov]

Good step forward, thanks!

[Dreamsorcerer]

I'll review this soonish and see if I can get the last issues resolved.

[Vizonex]

@Dreamsorcerer As someone who would like to see these features get added myself, I also made my own version before seeing this Pull Request that injects Paramspec correctly as well as correctly defining Class Methods with the use of Concatenate to determine if there is a class method being used perhaps I would be willing to step in and help you complete your Pull request

_Coro = Coroutine[Any, Any, _R]
_CB = Callable[_P, _Coro[_R]]
_CBOM = Union[_CB[_P, _R], _CB[Concatenate[Self, _P], _R]]
_CBP = Union[_CBOM[_P, _R], "partial[_Coro[_R]]", "partialmethod[_Coro[_R]]"]

I call _CBOM A "Callable Or Method" but I think I simplified it to _CBM in my PR if I remember correctly.

For some reason it didn't branch to your pull request specifically but I hope my additions to your pull request will at least excite you. I do give you credit though for coming up with this solution to begin with.
#639

[Dreamsorcerer]

OK, there's still some details not fully working with partial, but I think we can merge without that.

It's just the issue with methods that is blocking us now. I'm not sure how to fix it, it seems to me like the code is a little too complex for static typing.

The main issue seems to be this function which dynamically changes for an instance method:

async-lru/async_lru/__init__.py

Lines 227 to 233 in 0f20348

	def __get__(
	self, instance: _T, owner: Optional[Type[_T]]
	) -> Union[Self, "_LRUCacheWrapperInstanceMethod[_P, _R, _T]"]:
	if owner is None:
	return self
	else:
	return _LRUCacheWrapperInstanceMethod(self, instance)

The only thing I can think of is to try and split that class into 2 subclasses, rather than handling the logic within that get method. Then have a class that doesn't handle instance methods and another that does. The latter can then be defined with Concatenate (as Vizonex suggested) in order to remove the self parameter from the calling code. I don't have time or motivation to try this right now.

[Dreamsorcerer]

I can atleast use an overload for mypy to know that an instance method gets _LRUCacheWrapperInstanceMethod and another doesn't. But, still not sure how to get Concatenate into there without a separate class.

[Dreamsorcerer]

@Vizonex Not sure if you want to take another attempt at it, but we're down to 10 errors in mypy. 8 of them are due to the instance issue, so if you can get Concatenate to work correctly you should be able to get it down to 2 errors (you can literally just run the command mypy to test locally).

[Vizonex]

On Sun, Feb 2, 2025 at 4:30 PM Sam Bull ***@***.***> wrote: @Vizonex <https://github.com/Vizonex> Not sure if you want to take another attempt at it, but we're down to 10 errors in mypy. 8 of them are due to the instance issue, so if you can get Concatenate to work correctly you should be able to get it down to 2 errors. — Reply to this email directly, view it on GitHub <#508 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/A3K7GGVMOZ7QQAYNSNTQOVD2N2L7PAVCNFSM6AAAAAA2XK7FTKVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDMMRZGU4DQNBRGQ> . You are receiving this because you were mentioned.Message ID: ***@***.***>

Sounds good.