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Paramspec Mapped Types

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研究方向

先從 ParamSpec 範例和 issue 中要求的裝飾後簽名開始，然後檢視目前 Python typing 中關於參數包和可呼叫型別的語法。將所需的逐參數轉換與連結的 TypeScript mapped-tuple 範例進行比較；完成的標準是確定該語法是否能夠表達它，並記錄受支援的等價形式或限制。

由索引模型根據 Issue 內容生成。

描述

topic: other

Apologies if this has already been asked/solved - I can't figure out exactly what this is called so it's very difficult to search for.

I'm writing a simple strongly typed dependency system, based on function closures. I have a decorator function that has this typing:

# This is a stand-in for a full class implementation that has a __call__ method matching
# Callable[P, Awaitable[R]] - I'm just omitting it for brevity
type CallableObject[**P, R] = Callable[P, Awaitable[R]]

def dependency[**P, R](*args: P.args, **kwargs: P.kwargs) -> Callable[
    [Callable[P, Awaitable[R]] | Callable[P, R]], CallableObject
]:
    ...

This works to a degree, but, I want to transform the arguments in P to also accept functions that return the arguments type or an Awaitable of that type. For example:

def one() -> int:
    return 1

def two() -> int:
    return 2

@dependency()
def three(one: int, two: int) -> int:
    return one + two

# I want the decorated three to have this signature
def decorated_three(one: int | Callable[..., Awaitable[int] | int], two: int | Callable[..., Awaitable[int] | int]) -> int:
    ...

Essentially, I want to apply a mapping to every arg and kwarg in P that transforms it into P | Callable[..., Awaitable[P] | P]. Is this possible with the current grammar?

As a reference, I wrote an example that does what I'm attempting to do in typescript, where you can unpack what they call "type tuples" using the keyof syntax to mutate their values:

function dependency<P extends unknown[], R>(wrap: (...args: P) => R): (...args: {[V in keyof P]: P[V] | ((...args: any) => P[V] | Promise<P[V]>)}) => R {
    return wrap as any
}

function one(): number { return 1 }

function two(): number { return 2 }

function three(one: number, two: number): number { return one + two }

// Has type: const decorated_three: (one: number | ((...args: any) => number | Promise<number>), two: number | ((...args: any) => number | Promise<number>)) => number;
const decorated_three = dependency(three)

(Playground where you can see / verify the typing works as expected)

Apologies for dragging in another type system/language - I'm just looking for the python equivalent (if it exists).

Appreciate the help in advance. If this is a duplicate, please close it and mark it with the correct issue - I just couldn't find it 😅

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  3. Fork 儲存庫，在一個分支上完成修改。
  4. 送出 Pull Request，並在描述裡引用這個 Issue 編號。

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