PatchDict util (#1262)

* PatchDict utility

docs/docs/guides/response/django-pydantic.md

@@ -125,3 +125,31 @@ def patch(request, pk: int, payload: PatchGroupSchema):
 
 
 ```
+
+#### PatchDict
+
+Another way to work with patch request data is a `PatchDict` container which allows you to make 
+a schema with all optional fields and get a dict with **only** fields that was provide
+
+```Python hl_lines="1 11"
+from ninja import PatchDict
+
+class GroupSchema(Schema):
+    # You do not have to make fields optional it will be converted by PatchDict
+    name: str
+    description: str
+    due_date: date
+
+
+@api.patch("/patch/{pk}")
+def modify_data(request, pk: int, payload: PatchDict[GroupSchema]):
+    obj = MyModel.objects.get(pk=pk)
+
+    for attr, value in payload.items():
+        setattr(obj, attr, value)
+
+    obj.save()
+
+```
+
+in this example the `payload` argument will be a type of `dict` only fields that were passed in request and validated using `GroupSchema`

ninja/__init__.py

@@ -27,6 +27,7 @@
     Query,
     QueryEx,
 )
+from ninja.patch_dict import PatchDict
 from ninja.router import Router
 from ninja.schema import Schema
 
@@ -55,4 +56,5 @@
     "FilterSchema",
     "Swagger",
     "Redoc",
+    "PatchDict",
 ]

ninja/patch_dict.py

@@ -0,0 +1,52 @@
+from typing import TYPE_CHECKING, Any, Dict, Optional, Type
+
+from pydantic_core import core_schema
+from typing_extensions import Annotated
+
+from ninja import Body
+from ninja.utils import is_optional_type
+
+
+class ModelToDict(dict):
+    _wrapped_model: Any = None
+    _wrapped_model_dump_params: Dict[str, Any] = {}
+
+    @classmethod
+    def __get_pydantic_core_schema__(cls, _source: Any, _handler: Any) -> Any:
+        return core_schema.no_info_after_validator_function(
+            cls._validate,
+            cls._wrapped_model.__pydantic_core_schema__,
+        )
+
+    @classmethod
+    def _validate(cls, input_value: Any) -> Any:
+        return input_value.model_dump(**cls._wrapped_model_dump_params)
+
+
+def create_patch_schema(schema_cls: Type[Any]) -> Type[ModelToDict]:
+    values, annotations = {}, {}
+    for f in schema_cls.__fields__.keys():
+        t = schema_cls.__annotations__[f]
+        if not is_optional_type(t):
+            values[f] = getattr(schema_cls, f, None)
+            annotations[f] = Optional[t]
+    values["__annotations__"] = annotations
+    OptionalSchema = type(f"{schema_cls.__name__}Patch", (schema_cls,), values)
+
+    class OptionalDictSchema(ModelToDict):
+        _wrapped_model = OptionalSchema
+        _wrapped_model_dump_params = {"exclude_unset": True}
+
+    return OptionalDictSchema
+
+
+class PatchDictUtil:
+    def __getitem__(self, schema_cls: Any) -> Any:
+        new_cls = create_patch_schema(schema_cls)
+        return Body[new_cls]  # type: ignore
+
+
+if TYPE_CHECKING:  # pragma: nocover
+    PatchDict = Annotated[dict, "<PatchDict>"]
+else:
+    PatchDict = PatchDictUtil()

ninja/utils.py

@@ -50,6 +50,13 @@ def is_async_callable(f: Callable[..., Any]) -> bool:
     )
 
 
+def is_optional_type(t: Type[Any]) -> bool:
+    try:
+        return type(None) in t.__args__
+    except AttributeError:
+        return False
+
+
 def contribute_operation_callback(
     func: Callable[..., Any], callback: Callable[..., Any]
 ) -> None:

tests/test_patch_dict.py

@@ -0,0 +1,60 @@
+from typing import Optional
+
+import pytest
+
+from ninja import NinjaAPI, Schema
+from ninja.patch_dict import PatchDict
+from ninja.testing import TestClient
+
+api = NinjaAPI()
+
+client = TestClient(api)
+
+
+class SomeSchema(Schema):
+    name: str
+    age: int
+    category: Optional[str] = None
+
+
+@api.patch("/patch")
+def patch(request, payload: PatchDict[SomeSchema]):
+    return {"payload": payload, "type": str(type(payload))}
+
+
+@pytest.mark.parametrize(
+    "input,output",
+    [
+        ({"name": "foo"}, {"name": "foo"}),
+        ({"age": "1"}, {"age": 1}),
+        ({}, {}),
+        ({"wrong_param": 1}, {}),
+        ({"age": None}, {"age": None}),
+    ],
+)
+def test_patch_calls(input: dict, output: dict):
+    response = client.patch("/patch", json=input)
+    assert response.json() == {"payload": output, "type": "<class 'dict'>"}
+
+
+def test_schema():
+    "Checking that json schema properties are all optional"
+    schema = api.get_openapi_schema()
+    assert schema["components"]["schemas"]["SomeSchemaPatch"] == {
+        "title": "SomeSchemaPatch",
+        "type": "object",
+        "properties": {
+            "name": {
+                "anyOf": [{"type": "string"}, {"type": "null"}],
+                "title": "Name",
+            },
+            "age": {
+                "anyOf": [{"type": "integer"}, {"type": "null"}],
+                "title": "Age",
+            },
+            "category": {
+                "anyOf": [{"type": "string"}, {"type": "null"}],
+                "title": "Category",
+            },
+        },
+    }