Move field_name from runtime to schema generation time (#715)

Author: adriangb

python/pydantic_core/core_schema.py

@@ -1629,6 +1629,7 @@ class GeneralValidatorFunctionSchema(TypedDict):
 class FieldValidatorFunctionSchema(TypedDict):
     type: Literal['field']
     function: FieldValidatorFunction
+    field_name: str
 
 
 ValidationFunction = Union[NoInfoValidatorFunctionSchema, FieldValidatorFunctionSchema, GeneralValidatorFunctionSchema]
@@ -1691,6 +1692,7 @@ def fn(v: bytes) -> str:
 
 def field_before_validator_function(
     function: FieldValidatorFunction,
+    field_name: str,
     schema: CoreSchema,
     *,
     ref: str | None = None,
@@ -1710,7 +1712,7 @@ def fn(v: bytes, info: core_schema.FieldValidationInfo) -> str:
         return v.decode() + 'world'
 
     func_schema = core_schema.field_before_validator_function(
-        function=fn, schema=core_schema.str_schema()
+        function=fn, field_name='a', schema=core_schema.str_schema()
     )
     schema = core_schema.typed_dict_schema({'a': core_schema.typed_dict_field(func_schema)})
 
@@ -1720,14 +1722,15 @@ def fn(v: bytes, info: core_schema.FieldValidationInfo) -> str:
 
     Args:
         function: The validator function to call
+        field_name: The name of the field
         schema: The schema to validate the output of the validator function
         ref: optional unique identifier of the schema, used to reference the schema in other places
         metadata: Any other information you want to include with the schema, not used by pydantic-core
         serialization: Custom serialization schema
     """
     return _dict_not_none(
         type='function-before',
-        function={'type': 'field', 'function': function},
+        function={'type': 'field', 'function': function, 'field_name': field_name},
         schema=schema,
         ref=ref,
         metadata=metadata,
@@ -1826,6 +1829,7 @@ def fn(v: str) -> str:
 
 def field_after_validator_function(
     function: FieldValidatorFunction,
+    field_name: str,
     schema: CoreSchema,
     *,
     ref: str | None = None,
@@ -1845,7 +1849,7 @@ def fn(v: str, info: core_schema.FieldValidationInfo) -> str:
         return v + 'world'
 
     func_schema = core_schema.field_after_validator_function(
-        function=fn, schema=core_schema.str_schema()
+        function=fn, field_name='a', schema=core_schema.str_schema()
     )
     schema = core_schema.typed_dict_schema({'a': core_schema.typed_dict_field(func_schema)})
 
@@ -1855,14 +1859,15 @@ def fn(v: str, info: core_schema.FieldValidationInfo) -> str:
 
     Args:
         function: The validator function to call after the schema is validated
+        field_name: The name of the field
         schema: The schema to validate before the validator function
         ref: optional unique identifier of the schema, used to reference the schema in other places
         metadata: Any other information you want to include with the schema, not used by pydantic-core
         serialization: Custom serialization schema
     """
     return _dict_not_none(
         type='function-after',
-        function={'type': 'field', 'function': function},
+        function={'type': 'field', 'function': function, 'field_name': field_name},
         schema=schema,
         ref=ref,
         metadata=metadata,
@@ -1942,6 +1947,7 @@ class GeneralWrapValidatorFunctionSchema(TypedDict):
 class FieldWrapValidatorFunctionSchema(TypedDict):
     type: Literal['field']
     function: FieldWrapValidatorFunction
+    field_name: str
 
 
 WrapValidatorFunction = Union[
@@ -2053,6 +2059,7 @@ def fn(
 
 def field_wrap_validator_function(
     function: FieldWrapValidatorFunction,
+    field_name: str,
     schema: CoreSchema,
     *,
     ref: str | None = None,
@@ -2078,7 +2085,7 @@ def fn(
         return validator(v) + 'world'
 
     func_schema = core_schema.field_wrap_validator_function(
-        function=fn, schema=core_schema.str_schema()
+        function=fn, field_name='a', schema=core_schema.str_schema()
     )
     schema = core_schema.typed_dict_schema({'a': core_schema.typed_dict_field(func_schema)})
 
@@ -2088,14 +2095,15 @@ def fn(
 
     Args:
         function: The validator function to call
+        field_name: The name of the field
         schema: The schema to validate the output of the validator function
         ref: optional unique identifier of the schema, used to reference the schema in other places
         metadata: Any other information you want to include with the schema, not used by pydantic-core
         serialization: Custom serialization schema
     """
     return _dict_not_none(
         type='function-wrap',
-        function={'type': 'field', 'function': function},
+        function={'type': 'field', 'function': function, 'field_name': field_name},
         schema=schema,
         ref=ref,
         metadata=metadata,
@@ -2187,6 +2195,7 @@ def fn(v: str, info: core_schema.ValidationInfo) -> str:
 
 def field_plain_validator_function(
     function: FieldValidatorFunction,
+    field_name: str,
     *,
     ref: str | None = None,
     metadata: Any = None,
@@ -2204,7 +2213,7 @@ def fn(v: Any, info: core_schema.FieldValidationInfo) -> str:
         assert info.field_name is not None
         return str(v) + 'world'
 
-    func_schema = core_schema.field_plain_validator_function(function=fn)
+    func_schema = core_schema.field_plain_validator_function(function=fn, field_name='a')
     schema = core_schema.typed_dict_schema({'a': core_schema.typed_dict_field(func_schema)})
 
     v = SchemaValidator(schema)
@@ -2213,13 +2222,14 @@ def fn(v: Any, info: core_schema.FieldValidationInfo) -> str:
 
     Args:
         function: The validator function to call
+        field_name: The name of the field
         ref: optional unique identifier of the schema, used to reference the schema in other places
         metadata: Any other information you want to include with the schema, not used by pydantic-core
         serialization: Custom serialization schema
     """
     return _dict_not_none(
         type='function-plain',
-        function={'type': 'field', 'function': function},
+        function={'type': 'field', 'function': function, 'field_name': field_name},
         ref=ref,
         metadata=metadata,
         serialization=serialization,

src/validators/dataclass.rs

@@ -162,10 +162,6 @@ impl Validator for DataclassArgsValidator {
             ($args:ident, $get_method:ident, $get_macro:ident, $slice_macro:ident) => {{
                 // go through fields getting the value from args or kwargs and validating it
                 for (index, field) in self.fields.iter().enumerate() {
-                    let extra = Extra {
-                        field_name: Some(&field.name),
-                        ..extra
-                    };
                     let mut pos_value = None;
                     if let Some(args) = $args.args {
                         if !field.kw_only {
@@ -349,7 +345,6 @@ impl Validator for DataclassArgsValidator {
                 }
             }
             let next_extra = Extra {
-                field_name: Some(field_name),
                 data: Some(data_dict),
                 ..*extra
             };