🐛 Make sure a parameter defined as required is kept required in OpenAPI even if defined as optional in another dependency

fastapi/openapi/utils.py

@@ -166,6 +166,17 @@ def get_openapi_operation_metadata(
     return operation
 
 
+def get_openapi_operation_request_parameters(
+    *, parameters: List[Dict[str, Any]]
+) -> List[Dict[str, Any]]:
+    operation_request_parameters: Dict[str, Dict[str, Any]] = {}
+    for param in parameters:
+        if param["name"] not in operation_request_parameters or param["required"]:
+            operation_request_parameters[param["name"]] = param
+
+    return list(operation_request_parameters.values())
+
+
 def get_openapi_path(
     *, route: routing.APIRoute, model_name_map: Dict[type, str]
 ) -> Tuple[Dict[str, Any], Dict[str, Any], Dict[str, Any]]:
@@ -197,8 +208,8 @@ def get_openapi_path(
             )
             parameters.extend(operation_parameters)
             if parameters:
-                operation["parameters"] = list(
-                    {param["name"]: param for param in parameters}.values()
+                operation["parameters"] = get_openapi_operation_request_parameters(
+                    parameters=parameters
                 )
             if method in METHODS_WITH_BODY:
                 request_body_oai = get_openapi_operation_request_body(

tests/test_enforce_once_required_parameter.py

@@ -0,0 +1,105 @@
+from typing import Optional
+
+from fastapi import Depends, FastAPI, Query, status
+from fastapi.testclient import TestClient
+
+app = FastAPI()
+
+
+def _get_client_key(client_id: str = Query(...)) -> str:
+    return f"{client_id}_key"
+
+
+def _get_client_tag(client_id: Optional[str] = Query(None)) -> Optional[str]:
+    if client_id is None:
+        return None
+    return f"{client_id}_tag"
+
+
+@app.get("/foo")
+def foo_handler(
+    client_key: str = Depends(_get_client_key),
+    client_tag: Optional[str] = Depends(_get_client_tag),
+):
+    return {"client_id": client_key, "client_tag": client_tag}
+
+
+client = TestClient(app)
+
+expected_schema = {
+    "components": {
+        "schemas": {
+            "HTTPValidationError": {
+                "properties": {
+                    "detail": {
+                        "items": {"$ref": "#/components/schemas/ValidationError"},
+                        "title": "Detail",
+                        "type": "array",
+                    }
+                },
+                "title": "HTTPValidationError",
+                "type": "object",
+            },
+            "ValidationError": {
+                "properties": {
+                    "loc": {
+                        "items": {"type": "string"},
+                        "title": "Location",
+                        "type": "array",
+                    },
+                    "msg": {"title": "Message", "type": "string"},
+                    "type": {"title": "Error " "Type", "type": "string"},
+                },
+                "required": ["loc", "msg", "type"],
+                "title": "ValidationError",
+                "type": "object",
+            },
+        }
+    },
+    "info": {"title": "FastAPI", "version": "0.1.0"},
+    "openapi": "3.0.2",
+    "paths": {
+        "/foo": {
+            "get": {
+                "operationId": "foo_handler_foo_get",
+                "parameters": [
+                    {
+                        "in": "query",
+                        "name": "client_id",
+                        "required": True,
+                        "schema": {"title": "Client Id", "type": "string"},
+                    },
+                ],
+                "responses": {
+                    "200": {
+                        "content": {"application/json": {"schema": {}}},
+                        "description": "Successful " "Response",
+                    },
+                    "422": {
+                        "content": {
+                            "application/json": {
+                                "schema": {
+                                    "$ref": "#/components/schemas/HTTPValidationError"
+                                }
+                            }
+                        },
+                        "description": "Validation " "Error",
+                    },
+                },
+                "summary": "Foo Handler",
+            }
+        }
+    },
+}
+
+
+def test_schema():
+    response = client.get("/openapi.json")
+    assert response.status_code == status.HTTP_200_OK
+    actual_schema = response.json()
+    assert actual_schema == expected_schema
+
+
+def test_get_foo():
+    response = client.get("/foo", params={"client_id": None})
+    assert response.status_code == status.HTTP_422_UNPROCESSABLE_ENTITY