🐛 Fix empty reponse body when default `status_code` is empty but the a `Response` parameter with `response.status_code` is set (#5360)

Co-authored-by: Thomas Meckel <tmeckel@users.noreply.github.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Sebastián Ramírez <tiangolo@gmail.com>

fastapi/routing.py

@@ -258,7 +258,7 @@ def get_request_handler(
                 is_coroutine=is_coroutine,
             )
             response = actual_response_class(content, **response_args)
-            if not is_body_allowed_for_status_code(status_code):
+            if not is_body_allowed_for_status_code(response.status_code):
                 response.body = b""
             response.headers.raw.extend(sub_response.headers.raw)
             return response

tests/test_reponse_set_reponse_code_empty.py

@@ -0,0 +1,97 @@
+from typing import Any
+
+from fastapi import FastAPI, Response
+from fastapi.testclient import TestClient
+
+app = FastAPI()
+
+
+@app.delete(
+    "/{id}",
+    status_code=204,
+)
+async def delete_deployment(
+    id: int,
+    response: Response,
+) -> Any:
+    response.status_code = 400
+    return {"msg": "Status overwritten", "id": id}
+
+
+client = TestClient(app)
+
+
+openapi_schema = {
+    "openapi": "3.0.2",
+    "info": {"title": "FastAPI", "version": "0.1.0"},
+    "paths": {
+        "/{id}": {
+            "delete": {
+                "summary": "Delete Deployment",
+                "operationId": "delete_deployment__id__delete",
+                "parameters": [
+                    {
+                        "required": True,
+                        "schema": {"title": "Id", "type": "integer"},
+                        "name": "id",
+                        "in": "path",
+                    }
+                ],
+                "responses": {
+                    "204": {"description": "Successful Response"},
+                    "422": {
+                        "description": "Validation Error",
+                        "content": {
+                            "application/json": {
+                                "schema": {
+                                    "$ref": "#/components/schemas/HTTPValidationError"
+                                }
+                            }
+                        },
+                    },
+                },
+            }
+        }
+    },
+    "components": {
+        "schemas": {
+            "HTTPValidationError": {
+                "title": "HTTPValidationError",
+                "type": "object",
+                "properties": {
+                    "detail": {
+                        "title": "Detail",
+                        "type": "array",
+                        "items": {"$ref": "#/components/schemas/ValidationError"},
+                    }
+                },
+            },
+            "ValidationError": {
+                "title": "ValidationError",
+                "required": ["loc", "msg", "type"],
+                "type": "object",
+                "properties": {
+                    "loc": {
+                        "title": "Location",
+                        "type": "array",
+                        "items": {"anyOf": [{"type": "string"}, {"type": "integer"}]},
+                    },
+                    "msg": {"title": "Message", "type": "string"},
+                    "type": {"title": "Error Type", "type": "string"},
+                },
+            },
+        }
+    },
+}
+
+
+def test_openapi_schema():
+    response = client.get("/openapi.json")
+    assert response.status_code == 200, response.text
+    assert response.json() == openapi_schema
+
+
+def test_dependency_set_status_code():
+    response = client.delete("/1")
+    assert response.status_code == 400 and response.content
+    assert response.json() == {"msg": "Status overwritten", "id": 1}