Allow to register new class/dataclass/attribute makers in attrs plugin

@euresti

This is a feature request.

attrs is very much intended to be composable (e.g. https://github.com/hynek/environ_config) but currently the attrs plugin only works on the core library's functions:

mypy/mypy/plugins/attrs.py

Lines 24 to 37 in b2d6174

    
           # The names of the different functions that create classes or arguments. 
        
           attr_class_makers = { 
        
               'attr.s', 
        
               'attr.attrs', 
        
               'attr.attributes', 
        
           } 
        
           attr_dataclass_makers = { 
        
               'attr.dataclass', 
        
           } 
        
           attr_attrib_makers = { 
        
               'attr.ib', 
        
               'attr.attrib', 
        
               'attr.attr', 
        
           }

I would like to be able to signal somehow to mypy, that some function is a wrapper around @attr.s/@attr.ib/@attr.dataclass. Not only would third-party applications benefit, but I could really use it while experimenting on python-attrs/attrs#408.

Any ideas/plans how we could achieve that?

cc also @euresti & @chadrik

FYI in our code I literally append to these lists in a mypy plugin.

I did have a vision that the plugin could support an @class_maker(...) decorator that would do nothing at runtime but let the plugin know that this method (along with some default values) is a class_maker or attrib_maker.

So you'd do:

@class_maker(auto_attribs_default=True)
def my_class_maker(...):
   ...

Or something like that.

Another possible pattern we can support is:

if TYPE_CHECKING:
    custom_maker = attr.s
else:
    def custom_maker(cls):
        ...

The same problem exists for dataclasses, see #6239

Just FTR cross-posting the workaround that currently works:

from typing import TYPE_CHECKING
if TYPE_CHECKING:
    from attr import s as custom_maker
else:
    def custom_maker(cls):
        ...

but it is arguably worse than #5406 (comment), that currently doesn't work.

Heh. Here's what I did in our code base. I added a plugin that adds some methods when imported. (Did y'all wonder why I made those variables globals?)

from mypy.plugin import Plugin
from mypy.plugins.attrs import (
    attr_attrib_makers,
    attr_class_makers,
    attr_dataclass_makers,
)

# These work just like attr.dataclass
attr_dataclass_makers.add("my_module.method_looks_like_attr_dataclass")

# This work just like attr.s
attr_class_makers.add("my_module.method_looks_like_attr_s")

# These are our attr.ib makers.
attr_attrib_makers.add("my_module.method_looks_like_attrib")

class MyPlugin(Plugin):
    # Our plugin does nothing but it has to exist so this file gets loaded.
    pass


def plugin(version):
    return MyPlugin

Hah. Get mypy to not complain incorrectly about init args.

A checkup since it has been quite a long time. Are there any updates or cleaner workarounds?

I found from the mentions a cleaner one

if TYPE_CHECKING:
    from attrs import define
else:
    def define(cls):
        cls.__init_subclass__ = UnsupportedSubclassing.complain
        return attrs.define(cls)

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Allow to register new class/dataclass/attribute makers in attrs plugin #5406

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	# The names of the different functions that create classes or arguments.
	attr_class_makers = {
	'attr.s',
	'attr.attrs',
	'attr.attributes',
	}
	attr_dataclass_makers = {
	'attr.dataclass',
	}
	attr_attrib_makers = {
	'attr.ib',
	'attr.attrib',
	'attr.attr',
	}

Allow to register new class/dataclass/attribute makers in attrs plugin #5406

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euresti commented on Jul 31, 2018

ilevkivskyi commented on Aug 1, 2018

ilevkivskyi commented on Jan 22, 2019

ilevkivskyi commented on May 8, 2019

euresti commented on May 8, 2019

LecrisUT commented on Apr 9, 2026

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