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fastapi example: fix response_class #31

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gazpachoking merged 1 commit into from
Dec 29, 2025
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fastapi example: fix response_class #31

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6 changes: 3 additions & 3 deletions examples/fastapi/app.py
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,7 @@

import uvicorn
from fastapi import FastAPI
from fastapi.responses import HTMLResponse
from fastapi.responses import HTMLResponse, StreamingResponse

from datastar_py.fastapi import (
DatastarResponse,
Expand Down Expand Up @@ -59,7 +59,7 @@
"""


@app.get("/")
@app.get("/", response_class=HTMLResponse)
async def read_root():
return HTMLResponse(HTML.replace("CURRENT_TIME", f"{datetime.isoformat(datetime.now())}"))

Expand All @@ -76,7 +76,7 @@ async def time_updates():
await asyncio.sleep(1)


@app.get("/updates")
@app.get("/updates", response_class=StreamingResponse)
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@gazpachoking gazpachoking Dec 29, 2025

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Should it just be DatastarResponse? What does that do to the swagger?

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@joris-r joris-r Dec 29, 2025

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With response_class=StreamingResponse,
swagger only says there is no parameters and code 200 as Successful Response.
There is no media type documented at all (but previously it incorrectly indicated an application/json, so it's better that way).

So in this way, it's consistent.

With response_class=DatastarResponse,
swagger crash with Fetch error : Internal Server Error /openapi.json
The exception stack trace says:

...
        external_docs=self.openapi_external_docs,
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File "/home/joris/.cache/uv/environments-v2/app-df56c0d93ab9210a/lib/python3.13/site-packages/fastapi/openapi/utils.py", line 520, in get_openapi
    result = get_openapi_path(
        route=route,
    ...<3 lines>...
        separate_input_output_schemas=separate_input_output_schemas,
    )
  File "/home/joris/.cache/uv/environments-v2/app-df56c0d93ab9210a/lib/python3.13/site-packages/fastapi/openapi/utils.py", line 352, in get_openapi_path
    operation.setdefault("responses", {}).setdefault(status_code, {})[
                                                     ^^^^^^^^^^^
UnboundLocalError: cannot access local variable 'status_code' where it is not associated with a value

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@gazpachoking gazpachoking Dec 29, 2025

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Okay thanks for testing. Let's put it how you have for now. I'm curious if we could fix DatastarResponse to be usable as a response_class (for both swagger and automatically transforming the returns) and what that would look like. For the swagger purposes I still don't think it's that important, because a d* app would tend to be a non-api app.

async def updates(signals: ReadSignals):
# ReadSignals is a dependency that automatically loads the signals from the request
print(signals)
Expand Down
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