Forbid kwarg unpacking in class definition

[sobolevn]

Rule request

Thesis

We need to forbid code like this:

class Some(Base, **kwargs):
    ...

But, this code is valid:

class Some(Base, arg=1):
    ...

Reasoning

Dynamic class generation with unknown values is really bad!

[StutiV]

Hello, @sobolevn Can you assign me this issue? I'd like to contribute. Thanks.

[sobolevn]

Thanks a lot!

[StutiV]

Thank you, @sobolevn ! Can you please elaborate the issue? It'd be really helpful.

[sobolevn]

@StutiV what help do you need? I would love to answer speicific questions 🙂

[StutiV]

@sobolevn Which file should I be making these changes in?

[sobolevn]

@StutiV it is probably ast/classes.py. Feel free to choose the best visitor for the job.
https://github.com/wemake-services/wemake-python-styleguide/blob/master/wemake_python_styleguide/visitors/ast/classes.py

Probably WrongClassVisitor

[StakanAgan]

@sobolevn can you assign this issue for me?

[sobolevn]

@StakanAgan done! Thanks!

[thepabloaguilar]

@sobolevn do you have an example full example where a class receives parameters, please? Does the class need to have a metaclass or something like?

[sobolevn]

For example, this is fine:

from pydantic import BaseModel, Extra

class Model(BaseModel, extra=Extra.forbid):
    a: str

This is not (but will work the same way):

from pydantic import BaseModel, Extra

kw = {'extra': Extra.forbid}
class Model(BaseModel, **kw):
    a: str

Source: https://pydantic-docs.helpmanual.io/usage/model_config/