Fix issue #4740 https://github.com/tiangolo/fastapi/issues/4740

fastapi/openapi/utils.py

@@ -196,6 +196,8 @@ def get_openapi_operation_metadata(
     if route.description:
         operation["description"] = route.description
     operation_id = route.operation_id or route.unique_id
+    if len(route.methods) > 1:
+        operation_id = f'{operation_id}_{method.lower()}'
     if operation_id in operation_ids:
         message = (
             f"Duplicate Operation ID {operation_id} for function "

fastapi/utils.py

@@ -183,6 +183,7 @@ def generate_unique_id(route: "APIRoute") -> str:
     operation_id = route.name + route.path_format
     operation_id = re.sub(r"\W", "_", operation_id)
     assert route.methods
+    if len(route.methods) == 1:
         operation_id = operation_id + "_" + list(route.methods)[0].lower()
     return operation_id
 

tests/main.py

@@ -192,3 +192,8 @@ def get_enum_status_code():
 @app.get("/query/frozenset")
 def get_query_type_frozenset(query: FrozenSet[int] = Query(...)):
     return ",".join(map(str, sorted(query)))
+
+
+@app.api_route("/multiple-methods", methods=["GET", "POST"])
+def multiple_methods():
+    return {"message": "Hello World"}

tests/test_application.py

@@ -1163,9 +1163,46 @@ def test_openapi_schema():
                     },
                 }
             },
+            "/multiple-methods": {
+                "get": {
+                    "summary": "Multiple Methods",
+                    "operationId": "multiple_methods_multiple_methods_get",
+                    "responses": {
+                        "200": {
+                            "description": "Successful Response",
+                            "content": {"application/json": {"schema": {}}}
+                        }
+                    }
+                },
+                "post": {
+                    "summary": "Multiple Methods",
+                    "operationId": "multiple_methods_multiple_methods_post",
+                    "responses": {
+                        "200": {
+                            "description": "Successful Response",
+                            "content": {
+                                "application/json": {
+                                    "schema": {}
+                                }
+                            }
+                        }
+                    }
+                }
+            }
         },
         "components": {
             "schemas": {
+                "HTTPValidationError": {
+                    "title": "HTTPValidationError",
+                    "type": "object",
+                    "properties": {
+                        "detail": {
+                            "title": "Detail",
+                            "type": "array",
+                            "items": {"$ref": "#/components/schemas/ValidationError"},
+                        }
+                    },
+                },
                 "ValidationError": {
                     "title": "ValidationError",
                     "required": ["loc", "msg", "type"],
@@ -1182,17 +1219,6 @@ def test_openapi_schema():
                         "type": {"title": "Error Type", "type": "string"},
                     },
                 },
-                "HTTPValidationError": {
-                    "title": "HTTPValidationError",
-                    "type": "object",
-                    "properties": {
-                        "detail": {
-                            "title": "Detail",
-                            "type": "array",
-                            "items": {"$ref": "#/components/schemas/ValidationError"},
-                        }
-                    },
-                },
             }
         },
     }