🐛 Fix security schemes in OpenAPI when added at the top level app (#14266)

Co-authored-by: Sebastián Ramírez <tiangolo@gmail.com>

fastapi/dependencies/utils.py

@@ -248,6 +248,14 @@ def get_dependant(
     path_param_names = get_path_param_names(path)
     endpoint_signature = get_typed_signature(call)
     signature_params = endpoint_signature.parameters
+    if isinstance(call, SecurityBase):
+        use_scopes: List[str] = []
+        if isinstance(call, (OAuth2, OpenIdConnect)):
+            use_scopes = security_scopes
+        security_requirement = SecurityRequirement(
+            security_scheme=call, scopes=use_scopes
+        )
+        dependant.security_requirements.append(security_requirement)
     for param_name, param in signature_params.items():
         is_path_param = param_name in path_param_names
         param_details = analyze_param(
@@ -269,16 +277,6 @@ def get_dependant(
                 security_scopes=use_security_scopes,
                 use_cache=param_details.depends.use_cache,
             )
-            if isinstance(param_details.depends.dependency, SecurityBase):
-                use_scopes: List[str] = []
-                if isinstance(
-                    param_details.depends.dependency, (OAuth2, OpenIdConnect)
-                ):
-                    use_scopes = use_security_scopes
-                security_requirement = SecurityRequirement(
-                    security_scheme=param_details.depends.dependency, scopes=use_scopes
-                )
-                sub_dependant.security_requirements.append(security_requirement)
             dependant.dependencies.append(sub_dependant)
             continue
         if add_non_field_param_to_dependency(

tests/test_top_level_security_scheme_in_openapi.py

@@ -0,0 +1,60 @@
+# Test security scheme at the top level, including OpenAPI
+# Ref: https://github.com/fastapi/fastapi/discussions/14263
+# Ref: https://github.com/fastapi/fastapi/issues/14271
+from fastapi import Depends, FastAPI
+from fastapi.security import HTTPBearer
+from fastapi.testclient import TestClient
+from inline_snapshot import snapshot
+
+app = FastAPI()
+
+bearer_scheme = HTTPBearer()
+
+
+@app.get("/", dependencies=[Depends(bearer_scheme)])
+async def get_root():
+    return {"message": "Hello, World!"}
+
+
+client = TestClient(app)
+
+
+def test_get_root():
+    response = client.get("/", headers={"Authorization": "Bearer token"})
+    assert response.status_code == 200, response.text
+    assert response.json() == {"message": "Hello, World!"}
+
+
+def test_get_root_no_token():
+    response = client.get("/")
+    assert response.status_code == 403, response.text
+    assert response.json() == {"detail": "Not authenticated"}
+
+
+def test_openapi_schema():
+    response = client.get("/openapi.json")
+    assert response.status_code == 200, response.text
+    assert response.json() == snapshot(
+        {
+            "openapi": "3.1.0",
+            "info": {"title": "FastAPI", "version": "0.1.0"},
+            "paths": {
+                "/": {
+                    "get": {
+                        "summary": "Get Root",
+                        "operationId": "get_root__get",
+                        "responses": {
+                            "200": {
+                                "description": "Successful Response",
+                                "content": {"application/json": {"schema": {}}},
+                            }
+                        },
+                        "security": [{"HTTPBearer": []}],
+                    }
+                }
+            },
+            "components": {
+                "securitySchemes": {"HTTPBearer": {"type": "http", "scheme": "bearer"}}
+            },
+        }
+    )