model config in inheritance doesn't respect MRO

[KotlinIsland]

Initial Checks

• I confirm that I'm using Pydantic V2

Description

in the example below, the output should be True in my opinion because A is first in the mro.

Example Code

from pydantic import BaseModel, ConfigDict


class A(BaseModel):
    model_config = ConfigDict(strict=True)


class B(BaseModel):
    model_config = ConfigDict(strict=False)


class C(A, B):
    pass


print(C.model_config["strict"])  # False

Python, Pydantic & OS Version

pydantic version: 2.8.2
        pydantic-core version: 2.20.1
          pydantic-core build: profile=release pgo=true
                 install path: C:\Users\AMONGUS\projects\test\.venv\Lib\site-packages\pydantic
               python version: 3.12.2 (tags/v3.12.2:6abddd9, Feb  6 2024, 21:26:36) [MSC v.1937 64 bit (AMD64)]
                     platform: Windows-10-10.0.19045-SP0
             related packages: typing_extensions-4.12.2
                       commit: unknown

[sydney-runkle]

Hmm, I'm not convinced this should change - this would be a breaking change. When we merge fields, we respect the settings on the last field with the highest priority...

[sydney-runkle]

Ah yes, we've established this pattern in our docs:

When subclassing a model, the model_config attribute is inherited. This is helpful in the case where you'd like to use a base class with a given configuration for many models. Note, if you inherit from multiple BaseModel subclasses, like class MyModel(Model1, Model2), the non-default settings in the model_config attribute from the two models will be merged, and for any settings defined in both, those from Model2 will override those from Model1.

[KotlinIsland]

i find that very bizarre and unintuitive:

class A:
    a = 1
class B:
    a = 2
class C(A, B):
    pass
print(C.a)  # 1

[KotlinIsland]

@sydney-runkle was there any reasoning behind this pattern that you know of? what would it take to get it fixed?

[sydney-runkle]

@KotlinIsland,

I agree with you, this is a concerning pattern. Perhaps we could address in V3. I'll open and tag it as such.