Fix mypy error on free before validator (classmethod) (#8285)

pydantic/functional_validators.py

@@ -417,6 +417,21 @@ def __call__(  # noqa: D102
         ...
 
 
+class FreeModelBeforeValidatorWithoutInfo(Protocol):
+    """A @model_validator decorated function signature.
+    This is used when `mode='before'` and the function does not have info argument.
+    """
+
+    def __call__(  # noqa: D102
+        self,
+        # this can be a dict, a model instance
+        # or anything else that gets passed to validate_python
+        # thus validators _must_ handle all cases
+        __value: Any,
+    ) -> Any:
+        ...
+
+
 class ModelBeforeValidatorWithoutInfo(Protocol):
     """A @model_validator decorated function signature.
     This is used when `mode='before'` and the function does not have info argument.
@@ -433,6 +448,20 @@ def __call__(  # noqa: D102
         ...
 
 
+class FreeModelBeforeValidator(Protocol):
+    """A `@model_validator` decorated function signature. This is used when `mode='before'`."""
+
+    def __call__(  # noqa: D102
+        self,
+        # this can be a dict, a model instance
+        # or anything else that gets passed to validate_python
+        # thus validators _must_ handle all cases
+        __value: Any,
+        __info: _core_schema.ValidationInfo,
+    ) -> Any:
+        ...
+
+
 class ModelBeforeValidator(Protocol):
     """A `@model_validator` decorated function signature. This is used when `mode='before'`."""
 
@@ -457,7 +486,9 @@ def __call__(  # noqa: D102
 """A `@model_validator` decorated function signature. This is used when `mode='after'`."""
 
 _AnyModelWrapValidator = Union[ModelWrapValidator[_ModelType], ModelWrapValidatorWithoutInfo[_ModelType]]
-_AnyModeBeforeValidator = Union[ModelBeforeValidator, ModelBeforeValidatorWithoutInfo]
+_AnyModeBeforeValidator = Union[
+    FreeModelBeforeValidator, ModelBeforeValidator, FreeModelBeforeValidatorWithoutInfo, ModelBeforeValidatorWithoutInfo
+]
 _AnyModelAfterValidator = Union[ModelAfterValidator[_ModelType], ModelAfterValidatorWithoutInfo[_ModelType]]
 
 
@@ -499,8 +530,6 @@ def model_validator(
 
     Example usage:
     ```py
-    from typing import Optional
-
     from typing_extensions import Self
 
     from pydantic import BaseModel, ValidationError, model_validator
@@ -525,8 +554,7 @@ def verify_square(self) -> Self:
         print(e)
         '''
         1 validation error for Square
-        __root__
-          width and height do not match (type=value_error)
+          Value error, width and height do not match [type=value_error, input_value={'width': 1, 'height': 2}, input_type=dict]
         '''
     ```
 

tests/mypy/modules/success.py

@@ -42,6 +42,7 @@
     WrapValidator,
     create_model,
     field_validator,
+    model_validator,
     root_validator,
     validate_call,
 )
@@ -308,3 +309,15 @@ class Abstract(BaseModel):
 
 class Concrete(Abstract):
     class_id = 1
+
+
+def two_dim_shape_validator(v: Dict[str, Any]) -> Dict[str, Any]:
+    assert 'volume' not in v, 'shape is 2d, cannot have volume'
+    return v
+
+
+class Square(BaseModel):
+    width: float
+    height: float
+
+    free_validator = model_validator(mode='before')(two_dim_shape_validator)

tests/mypy/outputs/1.0.1/mypy-default_ini/success.py

@@ -42,6 +42,7 @@
     WrapValidator,
     create_model,
     field_validator,
+    model_validator,
     root_validator,
     validate_call,
 )
@@ -314,3 +315,15 @@ class Abstract(BaseModel):
 
 class Concrete(Abstract):
     class_id = 1
+
+
+def two_dim_shape_validator(v: Dict[str, Any]) -> Dict[str, Any]:
+    assert 'volume' not in v, 'shape is 2d, cannot have volume'
+    return v
+
+
+class Square(BaseModel):
+    width: float
+    height: float
+
+    free_validator = model_validator(mode='before')(two_dim_shape_validator)

tests/mypy/outputs/1.0.1/pyproject-default_toml/success.py

@@ -42,6 +42,7 @@
     WrapValidator,
     create_model,
     field_validator,
+    model_validator,
     root_validator,
     validate_call,
 )
@@ -314,3 +315,15 @@ class Abstract(BaseModel):
 
 class Concrete(Abstract):
     class_id = 1
+
+
+def two_dim_shape_validator(v: Dict[str, Any]) -> Dict[str, Any]:
+    assert 'volume' not in v, 'shape is 2d, cannot have volume'
+    return v
+
+
+class Square(BaseModel):
+    width: float
+    height: float
+
+    free_validator = model_validator(mode='before')(two_dim_shape_validator)