Fix issue with config decl at class level

changes/2532-uriyyo.md

@@ -0,0 +1,2 @@
+Fix bug with configurations declarations that are passed as
+keyword arguments during class creation.

pydantic/main.py

@@ -248,7 +248,12 @@ def __new__(mcs, name, bases, namespace, **kwargs):  # noqa C901
                 class_vars.update(base.__class_vars__)
                 hash_func = base.__hash__
 
-        config_kwargs = {key: kwargs.pop(key) for key in kwargs.keys() & BaseConfig.__dict__.keys()}
+        allowed_config_kwargs: SetStr = {
+            key
+            for key in dir(config)
+            if not (key.startswith('__') and key.endswith('__'))  # skip dunder methods and attributes
+        }
+        config_kwargs = {key: kwargs.pop(key) for key in kwargs.keys() & allowed_config_kwargs}
         config_from_namespace = namespace.get('Config')
         if config_kwargs and config_from_namespace:
             raise TypeError('Specifying config in two places is ambiguous, use either Config attribute or class kwargs')

tests/test_main.py

@@ -7,6 +7,7 @@
 import pytest
 
 from pydantic import (
+    BaseConfig,
     BaseModel,
     ConfigError,
     Extra,
@@ -1734,3 +1735,14 @@ class Model(BaseModel, extra='allow'):
 
             class Config:
                 extra = 'forbid'
+
+
+def test_class_kwargs_custom_config():
+    class Base(BaseModel):
+        class Config(BaseConfig):
+            some_config = 'value'
+
+    class Model(Base, some_config='new_value'):
+        a: int
+
+    assert Model.__config__.some_config == 'new_value'