bug: Fix handling an empty-body request with a required body param (#311)

* 🐛 Fix solving a required body param from an empty body request

* ✅ Add tests for receiving required body parameters with body not provided

fastapi/dependencies/utils.py

@@ -297,7 +297,7 @@ async def solve_dependencies(
     *,
     request: Union[Request, WebSocket],
     dependant: Dependant,
-    body: Dict[str, Any] = None,
+    body: Optional[Union[Dict[str, Any], FormData]] = None,
     background_tasks: BackgroundTasks = None,
     response: Response = None,
     dependency_overrides_provider: Any = None,
@@ -388,7 +388,7 @@ async def solve_dependencies(
     errors += path_errors + query_errors + header_errors + cookie_errors
     if dependant.body_params:
         body_values, body_errors = await request_body_to_args(  # type: ignore # body_params checked above
-            dependant.body_params, body
+            required_params=dependant.body_params, received_body=body
         )
         values.update(body_values)
         errors.extend(body_errors)
@@ -447,7 +447,8 @@ def request_params_to_args(
 
 
 async def request_body_to_args(
-    required_params: List[Field], received_body: Dict[str, Any]
+    required_params: List[Field],
+    received_body: Optional[Union[Dict[str, Any], FormData]],
 ) -> Tuple[Dict[str, Any], List[ErrorWrapper]]:
     values = {}
     errors = []
@@ -457,10 +458,14 @@ async def request_body_to_args(
         if len(required_params) == 1 and not embed:
             received_body = {field.alias: received_body}
         for field in required_params:
-            if field.shape in sequence_shapes and isinstance(received_body, FormData):
-                value = received_body.getlist(field.alias)
-            else:
-                value = received_body.get(field.alias)
+            value = None
+            if received_body is not None:
+                if field.shape in sequence_shapes and isinstance(
+                    received_body, FormData
+                ):
+                    value = received_body.getlist(field.alias)
+                else:
+                    value = received_body.get(field.alias)
             if (
                 value is None
                 or (isinstance(field.schema, params.Form) and value == "")

tests/test_tutorial/test_body_multiple_params/test_tutorial003.py

@@ -0,0 +1,172 @@
+import pytest
+from starlette.testclient import TestClient
+
+from body_multiple_params.tutorial003 import app
+
+client = TestClient(app)
+
+openapi_schema = {
+    "openapi": "3.0.2",
+    "info": {"title": "Fast API", "version": "0.1.0"},
+    "paths": {
+        "/items/{item_id}": {
+            "put": {
+                "responses": {
+                    "200": {
+                        "description": "Successful Response",
+                        "content": {"application/json": {"schema": {}}},
+                    },
+                    "422": {
+                        "description": "Validation Error",
+                        "content": {
+                            "application/json": {
+                                "schema": {
+                                    "$ref": "#/components/schemas/HTTPValidationError"
+                                }
+                            }
+                        },
+                    },
+                },
+                "summary": "Update Item",
+                "operationId": "update_item_items__item_id__put",
+                "parameters": [
+                    {
+                        "required": True,
+                        "schema": {"title": "Item_Id", "type": "integer"},
+                        "name": "item_id",
+                        "in": "path",
+                    }
+                ],
+                "requestBody": {
+                    "content": {
+                        "application/json": {
+                            "schema": {"$ref": "#/components/schemas/Body_update_item"}
+                        }
+                    },
+                    "required": True,
+                },
+            }
+        }
+    },
+    "components": {
+        "schemas": {
+            "Item": {
+                "title": "Item",
+                "required": ["name", "price"],
+                "type": "object",
+                "properties": {
+                    "name": {"title": "Name", "type": "string"},
+                    "price": {"title": "Price", "type": "number"},
+                    "description": {"title": "Description", "type": "string"},
+                    "tax": {"title": "Tax", "type": "number"},
+                },
+            },
+            "User": {
+                "title": "User",
+                "required": ["username"],
+                "type": "object",
+                "properties": {
+                    "username": {"title": "Username", "type": "string"},
+                    "full_name": {"title": "Full_Name", "type": "string"},
+                },
+            },
+            "Body_update_item": {
+                "title": "Body_update_item",
+                "required": ["item", "user", "importance"],
+                "type": "object",
+                "properties": {
+                    "item": {"$ref": "#/components/schemas/Item"},
+                    "user": {"$ref": "#/components/schemas/User"},
+                    "importance": {"title": "Importance", "type": "integer"},
+                },
+            },
+            "ValidationError": {
+                "title": "ValidationError",
+                "required": ["loc", "msg", "type"],
+                "type": "object",
+                "properties": {
+                    "loc": {
+                        "title": "Location",
+                        "type": "array",
+                        "items": {"type": "string"},
+                    },
+                    "msg": {"title": "Message", "type": "string"},
+                    "type": {"title": "Error Type", "type": "string"},
+                },
+            },
+            "HTTPValidationError": {
+                "title": "HTTPValidationError",
+                "type": "object",
+                "properties": {
+                    "detail": {
+                        "title": "Detail",
+                        "type": "array",
+                        "items": {"$ref": "#/components/schemas/ValidationError"},
+                    }
+                },
+            },
+        }
+    },
+}
+
+
+def test_openapi_schema():
+    response = client.get("/openapi.json")
+    assert response.status_code == 200
+    assert response.json() == openapi_schema
+
+
+# Test required and embedded body parameters with no bodies sent
+@pytest.mark.parametrize(
+    "path,body,expected_status,expected_response",
+    [
+        (
+            "/items/5",
+            {
+                "importance": 2,
+                "item": {"name": "Foo", "price": 50.5},
+                "user": {"username": "Dave"},
+            },
+            200,
+            {
+                "item_id": 5,
+                "importance": 2,
+                "item": {
+                    "name": "Foo",
+                    "price": 50.5,
+                    "description": None,
+                    "tax": None,
+                },
+                "user": {"username": "Dave", "full_name": None},
+            },
+        ),
+        (
+            "/items/5",
+            None,
+            422,
+            {
+                "detail": [
+                    {
+                        "loc": ["body", "item"],
+                        "msg": "field required",
+                        "type": "value_error.missing",
+                    },
+                    {
+                        "loc": ["body", "user"],
+                        "msg": "field required",
+                        "type": "value_error.missing",
+                    },
+                    {
+                        "loc": ["body", "importance"],
+                        "msg": "field required",
+                        "type": "value_error.missing",
+                    },
+                ]
+            },
+        ),
+    ],
+)
+def test_post_body(path, body, expected_status, expected_response):
+    response = client.put(path, json=body)
+    assert response.status_code == expected_status
+    assert response.json() == expected_response