pylint-dev/pylint

arguments-differ: number of parameters was some number ... and is now the same number in overridden ...

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#5,793 opened on Feb 11, 2022

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C: arguments-differDocumentation :green_book:Good first issue

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Description

Bug description

The following code produces a warning that does not really tell much about what is going wrong:

"""Comment."""
class Base:
    """Comment."""
    def fun(self, var: int) -> int:
        """Comment."""
        print(var)

class Class(Base):
    """Comment."""
    def fun(self, *, var: int) -> int:
        print(var)

Configuration

No response

Command used

pylint bug.py

Pylint output

************* Module bug
bug.py:15:4: W0221: Number of parameters was 2 in 'Base.fun' and is now 2 in overridden 'Class.fun' method (arguments-differ)

------------------------------------------------------------------
Your code has been rated at 8.33/10 (previous run: 8.33/10, +0.00)

Expected behavior

I'd expect a more meaningful warning not only referring to the number parameters (which has not changed from Base.fun to Class.fun).

Pylint version

pylint 2.12.2
astroid 2.9.3
Python 3.10.2 (main, Jan 17 2022, 14:26:36) [GCC 7.5.0]

OS / Environment

No response

Additional dependencies

No response

Contributor guide

Research direction
Investigate the pylint codebase for the 'arguments differ' message (W0221) to modify the warning text when the number of parameters is the same but their kind (e.g., positional vs keyword only) differs. The fix likely resides in the checker that compares method signatures.
Tech stack
python
Domain
developer experiencetooling
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
GitPython
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70