When making a dynamic member descriptor that can also behave as a Wrapper Why Does Self Not get deleted from ParamSpec?

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
25/100
Issue type
Documentation
Clarity
Needs clarification
Activity status
Stale
Tech stack
python
Domain
developer-experience

Research direction

Start with the supplied Python example and review the rules for ParamSpec, Self, Concatenate, and descriptor binding. Compare how mypy and pyright interpret the example, then determine whether the intended outcome requires a specification clarification or documentation change; done means the behavior and expected annotations are clearly decided.

Written by the indexing model from the issue text.

Description

topic: other

I've bumped into one of the largest and most frustrating puzzles I've ever encountered but I wanted to understand what the thought process behind ParamSpec was for class functions because I think if Self was ignored from ParamSpec dynamically based on weather or not a class function was in use it would not only fix lru_cache but it would also allow async_lru library to be type-hinted as well. No matter what I do, nothing works. I've tried multiple search engines to no avail so I go here now as my final resort since it's not a mypy problem because pyright is also plagued by the same rules.


from typing import ParamSpec, TypeVar, Callable, Protocol

P = ParamSpec("P")
T = TypeVar("T")
I = TypeVar("I")

# I made a class of my own for callable to illistrate the problem at hand.
class CallableProto(Protocol[P, T]):
    def __call__(self, *args:P.args, **kwds:P.kwargs) -> T:...

class RespectingCallable(CallableProto[P, T]):
    def __init__(self, func:Callable[P, T]):
        self.func = func
    # My question is Why does Self inside of a class function still get preserved in 
    # ParamSpec when it's just a class function? Shouldn't it get removed?
    # Also Concatenate doesn't work I've tried that one already with no success...
    def __get__(self, instance:I, obj:type[I]) -> CallableProto[P, T]:...

class A:
    def __init__(self) -> None:
        pass
    @RespectingCallable
    def coro(self, val:int) -> str:
        return f"{val}"

g = A()
# It appears as (self: A, val: int) -> str instead of (val: int) -> str 
# (mypy and pyright are also both are plagued by these rules)
g.coro(1)

@RespectingCallable
def func(i:int) -> str:
    return f"{i}"
# Somehow this is fine?
func(1)
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