Add a with_config decorator to comply with typing spec (#8611)

docs/api/config.md

@@ -3,6 +3,7 @@
       group_by_category: false
       members:
         - ConfigDict
+        - with_config
         - ExtraValues
         - BaseConfig
 

docs/concepts/config.md

@@ -57,7 +57,7 @@ from pydantic.dataclasses import dataclass
 config = ConfigDict(str_max_length=10, validate_assignment=True)
 
 
-@dataclass(config=config)  # (1)!
+@dataclass(config=config)
 class User:
     id: int
     name: str = 'John Doe'
@@ -76,26 +76,38 @@ except ValidationError as e:
     """
 ```
 
+## Configuration with `dataclass` from the standard library or `TypedDict`
 
-1. If using the `dataclass` from the standard library or `TypedDict`, you should use `__pydantic_config__` instead.
-   See:
+If using the `dataclass` from the standard library or `TypedDict`, you should use `__pydantic_config__` instead.
 
-    ```py
-    from dataclasses import dataclass
-    from datetime import datetime
+```py
+from dataclasses import dataclass
+from datetime import datetime
+
+from pydantic import ConfigDict
+
+
+@dataclass
+class User:
+    __pydantic_config__ = ConfigDict(strict=True)
+
+    id: int
+    name: str = 'John Doe'
+    signup_ts: datetime = None
+```
 
-    from pydantic import ConfigDict
+Alternatively, the [`with_config`][pydantic.config.with_config] decorator can be used to comply with type checkers.
 
+```py
+from typing_extensions import TypedDict
 
-    @dataclass
-    class User:
-        __pydantic_config__ = ConfigDict(strict=True)
+from pydantic import ConfigDict, with_config
 
-        id: int
-        name: str = 'John Doe'
-        signup_ts: datetime = None
-    ```
 
+@with_config(ConfigDict(str_to_lower=True))
+class Model(TypedDict):
+    x: str
+```
 
 ## Change behaviour globally
 

pydantic/__init__.py

@@ -19,7 +19,7 @@
     from ._internal._generate_schema import GenerateSchema as GenerateSchema
     from .aliases import AliasChoices, AliasGenerator, AliasPath
     from .annotated_handlers import GetCoreSchemaHandler, GetJsonSchemaHandler
-    from .config import ConfigDict
+    from .config import ConfigDict, with_config
     from .errors import *
     from .fields import Field, PrivateAttr, computed_field
     from .functional_serializers import (
@@ -80,6 +80,7 @@
     'WrapSerializer',
     # config
     'ConfigDict',
+    'with_config',
     # deprecated V1 config, these are imported via `__getattr__` below
     'BaseConfig',
     'Extra',
@@ -234,6 +235,7 @@
     'WrapSerializer': (__package__, '.functional_serializers'),
     # config
     'ConfigDict': (__package__, '.config'),
+    'with_config': (__package__, '.config'),
     # validate call
     'validate_call': (__package__, '.validate_call_decorator'),
     # errors

pydantic/config.py

@@ -1,7 +1,7 @@
 """Configuration for Pydantic models."""
 from __future__ import annotations as _annotations
 
-from typing import TYPE_CHECKING, Any, Callable, Dict, List, Type, Union
+from typing import TYPE_CHECKING, Any, Callable, Dict, List, Type, TypeVar, Union
 
 from typing_extensions import Literal, TypeAlias, TypedDict
 
@@ -11,7 +11,7 @@
 if TYPE_CHECKING:
     from ._internal._generate_schema import GenerateSchema as _GenerateSchema
 
-__all__ = ('ConfigDict',)
+__all__ = ('ConfigDict', 'with_config')
 
 
 JsonValue: TypeAlias = Union[int, float, str, bool, None, List['JsonValue'], 'JsonDict']
@@ -945,4 +945,40 @@ class Model(BaseModel):
     '''
 
 
+_TypeT = TypeVar('_TypeT', bound=type)
+
+
+def with_config(config: ConfigDict) -> Callable[[_TypeT], _TypeT]:
+    """Usage docs: https://docs.pydantic.dev/2.6/concepts/config/#configuration-with-dataclass-from-the-standard-library-or-typeddict
+
+    A convenience decorator to set a [Pydantic configuration](config.md) on a `TypedDict` or a `dataclass` from the standard library.
+
+    Although the configuration can be set using the `__pydantic_config__` attribute, it does not play well with type checkers,
+    especially with `TypedDict`.
+
+    !!! example "Usage"
+
+        ```py
+        from typing_extensions import TypedDict
+
+        from pydantic import ConfigDict, TypeAdapter, with_config
+
+        @with_config(ConfigDict(str_to_lower=True))
+        class Model(TypedDict):
+            x: str
+
+        ta = TypeAdapter(Model)
+
+        print(ta.validate_python({'x': 'ABC'}))
+        #> {'x': 'abc'}
+        ```
+    """
+
+    def inner(TypedDictClass: _TypeT, /) -> _TypeT:
+        TypedDictClass.__pydantic_config__ = config
+        return TypedDictClass
+
+    return inner
+
+
 __getattr__ = getattr_migration(__name__)

tests/mypy/modules/with_config_decorator.py

@@ -0,0 +1,11 @@
+from typing import TypedDict
+
+from pydantic import ConfigDict, with_config
+
+
+@with_config(ConfigDict(str_to_lower=True))
+class Model(TypedDict):
+    a: str
+
+
+model = Model(a='ABC')

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

@@ -0,0 +1,11 @@
+from typing import TypedDict
+
+from pydantic import ConfigDict, with_config
+
+
+@with_config(ConfigDict(str_to_lower=True))
+class Model(TypedDict):
+    a: str
+
+
+model = Model(a='ABC')

tests/mypy/outputs/1.1.1/pyproject-default_toml/with_config_decorator.py

@@ -0,0 +1,11 @@
+from typing import TypedDict
+
+from pydantic import ConfigDict, with_config
+
+
+@with_config(ConfigDict(str_to_lower=True))
+class Model(TypedDict):
+    a: str
+
+
+model = Model(a='ABC')

tests/mypy/test_mypy.py

@@ -110,6 +110,7 @@ def build(self) -> List[Union[Tuple[str, str], Any]]:
         ('mypy-plugin-strict-no-any.ini', 'dataclass_no_any.py'),
         ('mypy-plugin-very-strict.ini', 'metaclass_args.py'),
         ('pyproject-default.toml', 'computed_fields.py'),
+        ('pyproject-default.toml', 'with_config_decorator.py'),
     ]
 )
 

tests/test_dataclasses.py

@@ -32,6 +32,7 @@
     field_serializer,
     field_validator,
     model_validator,
+    with_config,
 )
 from pydantic._internal._mock_val_ser import MockValSer
 from pydantic.dataclasses import is_pydantic_dataclass, rebuild_dataclass
@@ -2406,6 +2407,24 @@ class Model:
     assert ta.validate_python({'x': 'ABC '}).x == 'ABC '
 
 
+def test_dataclasses_with_config_decorator():
+    @dataclasses.dataclass
+    @with_config(ConfigDict(str_to_lower=True))
+    class Model1:
+        x: str
+
+    ta = TypeAdapter(Model1)
+    assert ta.validate_python({'x': 'ABC'}).x == 'abc'
+
+    @with_config(ConfigDict(str_to_lower=True))
+    @dataclasses.dataclass
+    class Model2:
+        x: str
+
+    ta = TypeAdapter(Model2)
+    assert ta.validate_python({'x': 'ABC'}).x == 'abc'
+
+
 def test_pydantic_field_annotation():
     @pydantic.dataclasses.dataclass
     class Model:

tests/test_types_typeddict.py

@@ -20,6 +20,7 @@
     PositiveInt,
     PydanticUserError,
     ValidationError,
+    with_config,
 )
 from pydantic._internal._decorators import get_attribute_from_bases
 from pydantic.functional_serializers import field_serializer, model_serializer
@@ -919,3 +920,13 @@ class C(B):
         pass
 
     assert get_attribute_from_bases(C, 'x') == 2
+
+
+def test_typeddict_with_config_decorator():
+    @with_config(ConfigDict(str_to_lower=True))
+    class Model(TypedDict):
+        x: str
+
+    ta = TypeAdapter(Model)
+
+    assert ta.validate_python({'x': 'ABC'}) == {'x': 'abc'}