diff --git a/fastapi/dependencies/utils.py b/fastapi/dependencies/utils.py index 45e1ff3ed..ef8549b92 100644 --- a/fastapi/dependencies/utils.py +++ b/fastapi/dependencies/utils.py @@ -444,7 +444,9 @@ def analyze_param( depends = dataclasses.replace(depends, dependency=type_annotation) # Handle non-param type annotations like Request - if lenient_issubclass( + # Only apply special handling when there's no explicit Depends - if there's a Depends, + # the dependency will be called and its return value used instead of the special injection + if depends is None and lenient_issubclass( type_annotation, ( Request, @@ -455,7 +457,6 @@ def analyze_param( SecurityScopes, ), ): - assert depends is None, f"Cannot specify `Depends` for type {type_annotation!r}" assert field_info is None, ( f"Cannot specify FastAPI annotation for type {type_annotation!r}" ) diff --git a/tests/test_response_dependency.py b/tests/test_response_dependency.py new file mode 100644 index 000000000..1c600e484 --- /dev/null +++ b/tests/test_response_dependency.py @@ -0,0 +1,89 @@ +"""Test using Response type hint as dependency annotation.""" + +from typing import Annotated + +from fastapi import Depends, FastAPI, Response +from fastapi.testclient import TestClient + + +def test_response_with_depends_annotated(): + """Response type hint should work with Annotated[Response, Depends(...)].""" + app = FastAPI() + + def modify_response(response: Response) -> Response: + response.headers["X-Custom"] = "modified" + return response + + @app.get("/") + def endpoint(response: Annotated[Response, Depends(modify_response)]): + return {"status": "ok"} + + client = TestClient(app) + resp = client.get("/") + + assert resp.status_code == 200 + assert resp.json() == {"status": "ok"} + assert resp.headers.get("X-Custom") == "modified" + + +def test_response_with_depends_default(): + """Response type hint should work with Response = Depends(...).""" + app = FastAPI() + + def modify_response(response: Response) -> Response: + response.headers["X-Custom"] = "modified" + return response + + @app.get("/") + def endpoint(response: Response = Depends(modify_response)): + return {"status": "ok"} + + client = TestClient(app) + resp = client.get("/") + + assert resp.status_code == 200 + assert resp.json() == {"status": "ok"} + assert resp.headers.get("X-Custom") == "modified" + + +def test_response_without_depends(): + """Regular Response injection should still work.""" + app = FastAPI() + + @app.get("/") + def endpoint(response: Response): + response.headers["X-Direct"] = "set" + return {"status": "ok"} + + client = TestClient(app) + resp = client.get("/") + + assert resp.status_code == 200 + assert resp.json() == {"status": "ok"} + assert resp.headers.get("X-Direct") == "set" + + +def test_response_dependency_chain(): + """Response dependency should work in a chain of dependencies.""" + app = FastAPI() + + def first_modifier(response: Response) -> Response: + response.headers["X-First"] = "1" + return response + + def second_modifier( + response: Annotated[Response, Depends(first_modifier)], + ) -> Response: + response.headers["X-Second"] = "2" + return response + + @app.get("/") + def endpoint(response: Annotated[Response, Depends(second_modifier)]): + return {"status": "ok"} + + client = TestClient(app) + resp = client.get("/") + + assert resp.status_code == 200 + assert resp.headers.get("X-First") == "1" + assert resp.headers.get("X-Second") == "2"