mypy "Explicit "Any" is not allowed" error when extending BaseModel

[DetachHead]

Initial Checks

• I confirm that I'm using Pydantic V2

Description

in my codebase, we ban the Any type using the --disallow-any-explicit rule (along with all the other rules that ban Any in other contexts). when extending BaseModel, mypy complains with a no-any-explicit error.

this is annoying because it means we have to add a type:ignore comment on all of our classes that use BaseModel.

related issue: the dataclass decorator had the same problem (#4355), which i fixed in #4356. but i can't seem to figure out what's causing it in this case. i think it may be related to the pydantic mypy plugin?

Example Code

from pydantic import BaseModel

class Foo(BaseModel): # error: Explicit "Any" is not allowed (no-any-explicit)
    ...

Python, Pydantic & OS Version

pydantic version: 2.5.3
        pydantic-core version: 2.14.6
          pydantic-core build: profile=release pgo=true
                 install path: C:\Users\user\project\.venv\Lib\site-packages\pydantic
               python version: 3.12.0 (tags/v3.12.0:0fb18b0, Oct  2 2023, 13:03:39) [MSC v.1935 64 bit (AMD64)]
                     platform: Windows-11-10.0.22621-SP0
             related packages: typing_extensions-4.11.0

[DetachHead]

BaseModels with {"extra": "forbid"} do not have this issue:

class Foo(BaseModel): # no error
    model_config = ConfigDict(extra="forbid")

however, the mypy plugin does not seem to work when the config comes from a variable:

from pydantic import BaseModel, ConfigDict

default_config = ConfigDict(extra="forbid")

class Foo(BaseModel): # error: Explicit "Any" is not allowed (no-any-explicit)
    model_config = default_config

---

edit:

actually, even with {"extra": "forbid"}, they're still broken if there are any fields on them at all:

class Foo(BaseModel): # error
    model_config = ConfigDict(extra="forbid")
    foo: int # error goes away if you remove this

---

edit 2:

seems like configuring the mypy plugin with these options fixes it:

[tool.pydantic-mypy]
init_forbid_extra = true
init_typed = true

[sydney-runkle]

@DetachHead,

Hmm, thanks for reporting this. @dmontagu might have a better idea of how the mypy plugin relates to this issue. Let's see what he thinks!