Code Completion doesn't work for (class) functions decorated with decorators that return inner functions

Created February 15, 2022 13:02

So, decorated functions break down when when the decorator returns an inner function. This is not necessarily the case for stand-alone functions (unless they return other functions), but class functions show that effect immediately.

As can be seen, I get code completion for this class. But when I try to use code completion for return values, there's nothing:

Even though the viewer does have several functions, none are shown, as the returning type is "Any". If I explicitly name the type for the receiving variable, I have code completion:

So PyCharm does recognize the classes.

At the same time, none of the functions in that package give me parameter hints after I select a function:

As you can see (apart from the wrong documentation style) the function takes a file_name of type str, but the parameter hint only shows *args, **kwargs.

I don't have that problem in VS Code:

This does not happen in PyCharm 2020.2.5 nor in 2020.3

10 comments

Wickermoon

Created February 18, 2022 15:40

Update: So PyCharm 2021+ works with decorators, as long as those decorators don't return generic inner functions:

def simple_decorator(f: Callable[P, R]) -> Callable[P, R]:
    @wraps(f)
    def inner(*args: P.args, **kwargs: P.kwargs) -> R:
        try:
            return f(*args, **kwargs)
        except RemoteError as e:
            raise RemoteError(e.errormsg) from None
    return inner


def simple_decorator2(f):
    try:
        return f
    except RemoteError as e:
        raise RemoteError(e.errormsg) from None

The first decorator prevents parameter hinting (instead you just see P: ParamSpec("P")) and its return type is Any if used on a class function.

The second decorator does not prevent that. The try block is useless, but it's just to show why we need inner functions.

Wickermoon

Created February 22, 2022 10:11

At least some feedback on this issue would be nice. I mean, this bug literally breaks THE key feature of an IDE..code completion.

Wickermoon

Created March 01, 2022 13:38

Apparently code completion is not as important...

Pooyamohammadikazaj

Created November 29, 2022 10:38

Wickermoon could you solve the problem?

One more thing, what are P and R in your first comment?

Mdpgd95

Created March 31, 2023 01:06

Still happening for decorators returning `wrapper(*args, **kwargs)`

Build #PY-231.8109.197, built on March 29, 2023

Calix1999

Created May 04, 2023 22:25

Ran into something similar on IntelliJ `Build #IU-231.9011.4` with Python extension `231.9011.4` and the `@serde` decorator from `pyserde`. I get no autocomplete here:

@dataclass
@serde
class NoAutocomplete:
  f1: int
  f2: str

instance = NoAutocomplete(<no autocomplete here!>

If I remove the `@serde` decorator, autocomplete works normally. Here's the code for the `@serde` decorator at the time of writing:

@dataclass_transform()
def serde(
    _cls=None,
    **kwargs,
):  # type: ignore
    """
    serde decorator. Keyword arguments are passed in `serialize` and `deserialize`.
    """

    def wrap(cls):
        if should_impl_dataclass(cls):
            dataclass(cls)
        serialize(cls, **kwargs)
        deserialize(cls, **kwargs)
        return cls

    if _cls is None:
        return wrap  # type: ignore

    return wrap(_cls)