Make default operation IDs deterministic for multi-method routes

fastapi/utils.py

@@ -98,7 +98,8 @@ def generate_unique_id(route: "APIRoute") -> str:
     operation_id = f"{route.name}{route.path_format}"
     operation_id = re.sub(r"\W", "_", operation_id)
     assert route.methods
-    operation_id = f"{operation_id}_{list(route.methods)[0].lower()}"
+    method = sorted(route.methods)[0].lower()
+    operation_id = f"{operation_id}_{method}"
     return operation_id
 
 

tests/test_generate_unique_id_function.py

@@ -29,6 +29,14 @@ class Message(BaseModel):
     description: str
 
 
+def test_generate_unique_id_is_deterministic_with_multiple_methods():
+    def read_items():  # pragma: nocover - used for name only
+        return None
+
+    route = APIRoute("/items", read_items, methods=["POST", "GET"])
+    assert route.unique_id == "read_items_items_get"
+
+
 def test_top_level_generate_unique_id():
     app = FastAPI(generate_unique_id_function=custom_generate_unique_id)
     router = APIRouter()