RET504 "false positive" when using variables for typing

[autinerd]

Hello together,

When introducing the RET rules to Home Assistant I currently have this case (simplified):

def fun(a: dict[str, Any]) -> list[dict[str, Any]:
    services: list[dict[str, Any]]
    if "services" in a:
        services = a["services"]
        return services
    ... # services is further assigned and used

where RET504 is flagging, but when fixed mypy is complaining because of the Any type. The current options are 1. use cast, 2. declare the type again or 3. add a # noqa.

It would be cool that when a type declaration of the variable is found, that this assignment followed by a return would not get flagged.

[diceroll123]

You may want to have a be a TypedDict, something like

from typing import TypedDict, NotRequired, Any

class A_Type(TypedDict):
    services: NotRequired[list[dict[str, Any]]]

def fun(a: A_Type) -> list[dict[str, Any]]:
    services: list[dict[str, Any]]
    if "services" in a:
        return a["services"]
    # services being assigned other ways
    services = []
    return services

[autinerd]

In my case it is too versatile to have a TypedDict. https://github.com/home-assistant/core/pull/114528/files

https://github.com/home-assistant/core/pull/114528/files#diff-da81d27b5f83f07ead4bcbb0f29527511a2d7985acbe1cae45636e28202857ccR63-R74

hass.data is a dict which contains all kinds of different stuff for each integration/platform etc. in Home Assistant. There is currently work done to improve the typing topic, but until then we need these type annotations.

[charliermarsh]

I'm curious if you could do:

services: list[dict[str, Any]] = a["services"]
return services

That might be easier to "detect" / allow.

[autinerd]

I'm curious if you could do:

services: list[dict[str, Any]] = a["services"]
return services

That might be easier to "detect" / allow.

This is already working without issue, but then you have to annotate the variable multiple times.

[charliermarsh]

Oh, hah, I didn't realize that. I think we can support the variant from your first post.