How do you mark a FastAPI endpoint as deprecated?
Mark a FastAPI route with deprecated=True on its path operation decorator. FastAPI emits the OpenAPI deprecated flag, which Swagger UI can display; this metadata does not remove or disable the route.
Put deprecated=True on the path operation decorator. FastAPI writes the OpenAPI deprecated flag for that operation, and Swagger UI can render the route as deprecated.
Example
from fastapi import FastAPI
app = FastAPI()
@app.get('/users/by-id', deprecated=True)
async def get_user_by_id(user_id: int):
return {'user_id': user_id}Watch out for
This changes generated API metadata; it does not block requests, remove the route, or create a sunset date. A docstring may become the operation description, but it does not set the deprecated flag.
Interview question
How do you correctly mark a FastAPI endpoint as deprecated so Swagger UI displays it struck through?
- a.Pass deprecated=True directly to the path operation decorator such as @app.get(..., deprecated=True)Correct
- b.Add deprecated=True to the Pydantic Field definitions in the endpoint's request or response model
- c.Write a deprecation warning inside the function docstring for Swagger UI to parse
- d.Mutate the raw OpenAPI dictionary after startup using app.openapi() to set the route flag manually
Why? this is the answer
FastAPI reads deprecated=True from the path operation decorator and writes the deprecated field into the generated OpenAPI operation, which Swagger UI can render with a strikethrough. A docstring may appear as the operation description, but it does not set the deprecated flag for tools or replace the decorator argument.
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