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Autofix B006 (mutable-argument-default) #4693

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auscompgeek opened this issue May 28, 2023 · 1 comment · Fixed by #6131
Closed

Autofix B006 (mutable-argument-default) #4693

auscompgeek opened this issue May 28, 2023 · 1 comment · Fixed by #6131
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@qdegraaf
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fixes Related to suggested fixes for violations

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@auscompgeek
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B006 could have an autofixer to instead make the default None and check if it is None within the function.

pybetter includes a fixer for this:

Default values for kwargs are mutable.

As described in Common Gotchas section of "The Hitchhiker's Guide to Python", mutable arguments can be a tricky thing. This fixer replaces any default values that happen to be lists or dicts with None value, moving initialization from function definition into function body.

# BEFORE
def p(a=[]):
    print(a)

# AFTER
def p(a=None):
    if a is None:
        a = []
    
    print(a)

Be warned, that this fix may break code which intentionally uses mutable default arguments (e.g. caching).

This may want to also autofix the type hint to be Optional if there is one.
@charliermarsh charliermarsh added the fixes Related to suggested fixes for violations label May 29, 2023
@qdegraaf
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qdegraaf commented Jun 4, 2023

I'll give this one a go

@qdegraaf qdegraaf mentioned this issue Jun 5, 2023
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@qdegraaf qdegraaf mentioned this issue Jul 27, 2023
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konstin added a commit that referenced this issue Aug 10, 2023
@qdegraaf @konstin
[flake8-bugbear] Add autofix for B006 (#6131)
50dab9c 
## Summary

Reopening of #4880 

One open TODO as described in:
#4880 (comment)

FYI @charliermarsh seeing as you commented you wanted to do final review
and merge. @konstin @dhruvmanila @MichaReiser as previous reviewers.

# Old Description
## Summary

Adds an autofix for B006 turning mutable argument defaults into None and
setting their original value back in the function body if still `None`
at runtime like so:
```python
def before(x=[]):
    pass
    
def after(x=None):
    if x is None:
        x = []
    pass
```

## Test Plan

Added an extra test case to existing fixture with more indentation.
Checked results for all old examples.

NOTE: Also adapted the jupyter notebook test as this checked for B006 as
well.

## Issue link

Closes: #4693

---------

Co-authored-by: konstin <[email protected]>
durumu pushed a commit to durumu/ruff that referenced this issue Aug 12, 2023
@qdegraaf @konstin @durumu
[flake8-bugbear] Add autofix for B006 (astral-sh#6131)
fdfd44b 
## Summary

Reopening of astral-sh#4880 

One open TODO as described in:
astral-sh#4880 (comment)

FYI @charliermarsh seeing as you commented you wanted to do final review
and merge. @konstin @dhruvmanila @MichaReiser as previous reviewers.

# Old Description
## Summary

Adds an autofix for B006 turning mutable argument defaults into None and
setting their original value back in the function body if still `None`
at runtime like so:
```python
def before(x=[]):
    pass
    
def after(x=None):
    if x is None:
        x = []
    pass
```

## Test Plan

Added an extra test case to existing fixture with more indentation.
Checked results for all old examples.

NOTE: Also adapted the jupyter notebook test as this checked for B006 as
well.

## Issue link

Closes: astral-sh#4693

---------

Co-authored-by: konstin <[email protected]>
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