Remove unnecessary warning for config in plugin

pydantic/mypy.py

@@ -957,7 +957,11 @@ def get_config_update(self, name: str, arg: Expression) -> ModelConfigData | Non
             elif isinstance(arg, MemberExpr):
                 forbid_extra = arg.name == 'forbid'
             else:
-                error_invalid_config_value(name, self._api, arg)
+                # Do not emit an error for other types of `arg` (e.g., `NameExpr`, `ConditionalExpr`, etc.)
+                # It would be nice if we could type-check these better, but I don't know what the API is to
+                # evaluate an expr into its type and then check if that type is compatible with the expected type.
+                # Note that you can still get proper type checking via: `model_config = ConfigDict(...)`, it's just that
+                # if you don't use an explicit string, the plugin won't be able to infer whether extra is forbidden.
                 return None
             return ModelConfigData(forbid_extra=forbid_extra)
         if name == 'alias_generator':

tests/mypy/modules/config_conditional_extra.py

@@ -0,0 +1,9 @@
+from pydantic import BaseModel, ConfigDict
+
+
+def condition() -> bool:
+    return True
+
+
+class MyModel(BaseModel):
+    model_config = ConfigDict(extra='ignore' if condition() else 'forbid')

tests/mypy/test_mypy.py

@@ -87,7 +87,6 @@ def build(self) -> List[Union[Tuple[str, str], Any]]:
             'plugin_fail.py',
             'plugin_success_baseConfig.py',
             'plugin_fail_baseConfig.py',
-            'plugin_optional_inheritance.py',
             'pydantic_settings.py',
         ],
     ).build()
@@ -105,6 +104,8 @@ def build(self) -> List[Union[Tuple[str, str], Any]]:
     # One-off cases
     + [
         ('mypy-plugin.ini', 'custom_constructor.py'),
+        ('mypy-plugin.ini', 'config_conditional_extra.py'),
+        ('mypy-plugin.ini', 'plugin_optional_inheritance.py'),
         ('mypy-plugin.ini', 'generics.py'),
         ('mypy-plugin.ini', 'root_models.py'),
         ('mypy-plugin-strict.ini', 'plugin_default_factory.py'),