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Forbid assigning lambda to object properties #1733

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sobolevn opened this issue Nov 19, 2020 · 7 comments · May be fixed by #1911
Open

Forbid assigning lambda to object properties #1733

sobolevn opened this issue Nov 19, 2020 · 7 comments · May be fixed by #1911
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help wanted Extra attention is needed level:starter Good for newcomers pr-available rule request Adding a new rule
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Version 0.17.0 ak...

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@sobolevn
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Rule request

Thesis

We should forbid code like:

class Example(object):
    def __init__(self):
        self.callback = lambda arg: arg + 1

Reasoning

This will be very tricky to understand for users: example.callback(1) will look like a method, but it is not a method.
@sobolevn sobolevn added help wanted Extra attention is needed level:starter Good for newcomers rule request Adding a new rule labels Nov 19, 2020
@sobolevn sobolevn added this to the Version 0.15 aka Python3.9 milestone Nov 19, 2020
@abhi-krish
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Hi! I'd like to work on this.

@sobolevn
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Awesome! Thanks a lot!

@abhi-krish
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Hey @sobolevn! This is my first time contributing and am not sure where I should start with this problem. Would you be able to point me in the right direction?

@sobolevn
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Sure!

Start with reading this file: https://github.com/wemake-services/wemake-python-styleguide/blob/master/CONTRIBUTING.md
Then look at: https://github.com/wemake-services/wemake-python-styleguide/blob/master/wemake_python_styleguide/visitors/ast/classes.py

@abhi-krish abhi-krish removed their assignment Nov 30, 2020
@sobolevn
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@willtkwon Please feel free! And thank you 🙂

@AlexandrKhabarov
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Is it correct that this check should find situations like this?

create_object.attr = lambda: print('Lambda!')

I mean that it should not distinguish lambda assignemnts inside init or anywehere.

@sobolevn
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We only treat self, cls, and mcs as self-like objects. So, we only check them. See https://github.com/wemake-services/wemake-python-styleguide/blob/master/wemake_python_styleguide/constants.py#L150

@sobolevn sobolevn linked a pull request Feb 25, 2021 that will close this issue
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@sobolevn sobolevn linked a pull request Feb 25, 2021 that will close this issue
1733 add lambda instance assignment violation #1911
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4 tasks
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help wanted Extra attention is needed level:starter Good for newcomers pr-available rule request Adding a new rule
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Version 0.17.0 aka Python3.10
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1733 add lambda instance assignment violation AlexandrKhabarov/wemake-python-styleguide
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@sobolevn @AlexandrKhabarov @abhi-krish