fix: generate unique operation ids for multi-method routes

fastapi/openapi/utils.py

@@ -31,6 +31,7 @@ from fastapi.responses import Response
 from fastapi.sse import _SSE_EVENT_SCHEMA
 from fastapi.types import ModelNameMap
 from fastapi.utils import (
+    _generate_unique_id_for_method,
     deep_dict_update,
     generate_operation_id_for_path,
     is_body_allowed_for_status_code,
@@ -242,7 +243,15 @@ def get_openapi_operation_metadata(
     operation["summary"] = generate_operation_summary(route=route, method=method)
     if route.description:
         operation["description"] = route.description
-    operation_id = route.operation_id or route.unique_id
+    if (
+        route.operation_id is None
+        and isinstance(route.generate_unique_id_function, DefaultPlaceholder)
+        and route.methods
+        and len(route.methods) > 1
+    ):
+        operation_id = _generate_unique_id_for_method(route, method=method)
+    else:
+        operation_id = route.operation_id or route.unique_id
     if operation_id in operation_ids:
         endpoint_name = getattr(route.endpoint, "__name__", "<unnamed_endpoint>")
         message = f"Duplicate Operation ID {operation_id} for function {endpoint_name}"

fastapi/utils.py

@@ -92,14 +92,18 @@ def generate_operation_id_for_path(
     return operation_id
 
 
-def generate_unique_id(route: "APIRoute") -> str:
+def _generate_unique_id_for_method(route: "APIRoute", method: str) -> 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()}"
+    operation_id = f"{operation_id}_{method.lower()}"
     return operation_id
 
 
+def generate_unique_id(route: "APIRoute") -> str:
+    assert route.methods
+    return _generate_unique_id_for_method(route, method=list(route.methods)[0])
+
+
 def deep_dict_update(main_dict: dict[Any, Any], update_dict: dict[Any, Any]) -> None:
     for key, value in update_dict.items():
         if (

tests/test_generate_unique_id_function.py

@@ -1697,3 +1697,33 @@ def test_warn_duplicate_operation_id():
         ]
         assert len(duplicate_warnings) > 0
         assert "Duplicate Operation ID" in str(duplicate_warnings[0].message)
+
+
+def test_multi_method_route_unique_operation_ids():
+    app = FastAPI()
+
+    def clear():
+        return {"ok": True}  # pragma: nocover
+
+    app.add_api_route("/clear", clear, methods=["POST", "DELETE"])
+
+    client = TestClient(app)
+    with warnings.catch_warnings(record=True) as w:
+        warnings.simplefilter("always")
+        response = client.get("/openapi.json")
+        assert response.status_code == 200, response.text
+
+    duplicate_warnings = [
+        warning
+        for warning in w
+        if issubclass(warning.category, UserWarning)
+        and "Duplicate Operation ID" in str(warning.message)
+    ]
+    assert duplicate_warnings == []
+    openapi_schema = response.json()
+    assert openapi_schema["paths"]["/clear"]["post"]["operationId"] == (
+        "clear_clear_post"
+    )
+    assert openapi_schema["paths"]["/clear"]["delete"]["operationId"] == (
+        "clear_clear_delete"
+    )