used-before-assignment false negative with TYPE_CHECKING

[DanielNoord]

Bug description

Within functions used-before-assignment doesn't get raised for some edge cases.

from typing import TYPE_CHECKING

if TYPE_CHECKING:
    from datetime import datetime

# pylint: disable=missing-function-docstring, missing-module-docstring


def func_two():
    second = datetime.now()
    return second


def func():
    first: datetime
    first = datetime.now()
    second = datetime.now()
    return first, second

Configuration

Default config.

Command used

pylint

Pylint output

************* Module test
test.py:10: [E0601(used-before-assignment), func_two] Using variable 'datetime' before assignment


-------------------------------------------------------------------
Your code has been rated at 4.55/10 (previous run: 10.00/10, -5.45)

Expected behavior

************* Module test
test.py:10: [E0601(used-before-assignment), func_two] Using variable 'datetime' before assignment
test.py:16: [E0601(used-before-assignment), func_two] Using variable 'datetime' before assignment


-------------------------------------------------------------------
Your code has been rated at 4.55/10 (previous run: 10.00/10, -5.45)

Pylint version

2.16.1

OS / Environment

/

Additional dependencies

No response

[jacobtylerwalls]

Is this still a problem as of #8071?

[MaximMukhametov]

Is this still a problem as of #8071?

yes, I have the same problem with:

from typing import TYPE_CHECKING
# It's needed just to avoid the PyCharm's static analyzer bug
# https://stackoverflow.com/questions/53276766/how-to-avoid-unexpected-argument-warning-using-data-classes
if TYPE_CHECKING:
    from dataclasses import dataclass  # noqa
else:
    from pydantic.dataclasses import dataclass  # noqa


@dataclass
class Item:
    """Item domain model."""

    user_id: int
    title: str
    id: int | None = None

[DanielNoord]

@jacobtylerwalls Yeah, on main this is still an issue.. I wonder if we could expand on that PR?

[zenlyj]

@DanielNoord if no one has started on this, could you assign it to me? Thanks! 🙂

[zenlyj]

@MaximMukhametov i am struggling to understand why used-before-assignment should be emitted in your example. Isn't dataclass defined by this line: from pydantic.dataclasses import dataclass? Please let me know if I am missing something here.

[jacobtylerwalls]

@zenlyj pylint is taking into account that if TYPE_CHECKING: will be false at runtime. Add the line func() at the bottom of Daniël's example, and execute it. You will see:

    first = datetime.now()
            ^^^^^^^^
NameError: name 'datetime' is not defined

[zenlyj]

@jacobtylerwalls thanks for clarifying! Any thoughts on the other case posted by @MaximMukhametov? I am unsure if the dataclass decorator should raise used-before-assignment, since it is defined in the else block.

[jacobtylerwalls]

Ah, sorry! You have a point; doesn't seem like we should emit warnings in that case (and we don't currently.)