Update wrap_jsonp to handle lists

[jimchamp]

Addresses regression identified here

starlette.responses.Response.render is throwing an AttributeError when data is a list. These changes ensure that lists are also serialized.

Technical

Testing

Screenshot

Stakeholders

@RayBB
@cdrini

[Copilot]

Pull request overview

Updates the FastAPI wrap_jsonp helper to correctly JSON-serialize list responses, preventing starlette.responses.Response.render errors when endpoints return [].

Changes:

• Expand wrap_jsonp input type to accept list in addition to dict/str.
• Serialize dict/list inputs via json.dumps while preserving pre-serialized JSON strings.
• Add an explicit type guard for unexpected data types.

Comments suppressed due to low confidence (1)

openlibrary/fastapi/models.py:77

• wrap_jsonp raises ValueError when the callback query param is invalid. Since this helper is used directly in FastAPI route handlers (e.g., openlibrary/fastapi/books.py) and there is no global exception handler for ValueError in the ASGI app, this will surface as a 500 error for a client-supplied bad callback. Prefer raising HTTPException(status_code=400, ...) so invalid user input returns a 4xx response (and update the existing unit test that currently expects ValueError).

    if callback := request.query_params.get("callback"):
        if not JS_CALLBACK_RE.match(callback):
            raise ValueError("Invalid callback parameter: must be a valid JavaScript identifier (only letters, numbers, underscore, $, and . allowed)")
        return Response(content=f"{callback}({json_string});", media_type="application/javascript")

[Copilot]

List support was added to wrap_jsonp (serializing list via json.dumps), but the existing unit tests for wrap_jsonp (see openlibrary/tests/fastapi/test_models.py) don’t cover the list case. Please add a test that passes a list (with and without a callback) to prevent this regression from reappearing.

[jimchamp]

@copilot apply changes based on this feedback

[Copilot]

Implemented in 81fbb53. I added regression tests in openlibrary/tests/fastapi/test_models.py covering list payloads for both cases: no callback (application/json) and with callback (application/javascript).

[Copilot]

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