docs: SQLAlchemyInitPlugin to SQLAlchemyPlugin fixes SerializationException for docs

[JorenSix]

Description

This fixes a SerializationException when running the demo with dummy data included. The example now is fixed by using the SQLAlchemyPlugin in stead of the SQLAlchemyInitPlugin and dummy data is added which immediately shows the expected behaviour: a JSON list with authors.

See issue #3464

Closes

Closes #3464

[peterschutt]

Thanks @JorenSix!

Beyond the missing serialization plugin, I like the idea of seeding the database with some test data!

We really should have a test for the example in tests/examples/test_contrib/test_sqlalchemy, would you mind adding one as part of this PR? It should hit the GET /authors endpoint and test the json response.

[JorenSix]

I have modified the example using the suggestions above. The metadata is now created automatically, the data via on_startup.

I also created a new unit test file which checks if the response is 200 and a non empty list of authors is returned. This works with recent python versions.

Unfortunately this fails for older python versions (3.9, 3.10), which immediately shows why it is indeed a good idea to provide a unit test. The litestar.exceptions.base_exceptions.SerializationException looks similar to me as the original associated issue #3464

Traceback (most recent call last):
  File "/workspaces/litestar/litestar/middleware/_internal/exceptions/middleware.py", line 158, in __call__
    await self.app(scope, receive, capture_response_started)
  File "/workspaces/litestar/litestar/_asgi/asgi_router.py", line 99, in __call__
    await asgi_app(scope, receive, send)
  File "/workspaces/litestar/litestar/routes/http.py", line 80, in handle
    response = await self._get_response_for_request(
  File "/workspaces/litestar/litestar/routes/http.py", line 132, in _get_response_for_request
    return await self._call_handler_function(
  File "/workspaces/litestar/litestar/routes/http.py", line 156, in _call_handler_function
    response: ASGIApp = await route_handler.to_response(app=scope["app"], data=response_data, request=request)
  File "/workspaces/litestar/litestar/handlers/http_handlers/base.py", line 557, in to_response
    return await response_handler(app=app, data=data, request=request)  # type: ignore[call-arg]
  File "/workspaces/litestar/litestar/handlers/http_handlers/_utils.py", line 79, in handler
    return response.to_asgi_response(app=None, request=request, headers=normalize_headers(headers), cookies=cookies)  # pyright: ignore
  File "/workspaces/litestar/litestar/response/base.py", line 451, in to_asgi_response
    body=self.render(self.content, media_type, get_serializer(type_encoders)),
  File "/workspaces/litestar/litestar/response/base.py", line 392, in render
    return encode_json(content, enc_hook)
  File "/workspaces/litestar/litestar/serialization/msgspec_hooks.py", line 152, in encode_json
    raise SerializationException(str(msgspec_error)) from msgspec_error
litestar.exceptions.base_exceptions.SerializationException: Unsupported type: <class 'docs.examples.contrib.sqlalchemy.sqlalchemy_declarative_models.Book'>

Feedback or instructions on how to proceed are welcome.

As an aside: I already learned a lot about the litestar CI infra and the use of the .devcontainer folder. Very practical indeed to e.g. switch python versions and quickly run unit tests.

[Alc-Alc]

@JorenSix can you try this change?

books: "Mapped[list[Book]]" = relationship(back_populates="author", lazy="selectin")

which immediately shows why it is indeed a good idea to provide a unit test.

@Kumzy has a related (ish) PR #3445 here that would make sure all code examples are tested

[github-actions]

Documentation preview will be available shortly at https://litestar-org.github.io/litestar-docs-preview/3475

[JorenSix]

Thanks for following up and the quick feedback. The process and the infrastructure of litestar seems exemplary. I learned a lot about how you handle things here. Thanks again.

[peterschutt]

@all-contributors add @JorenSix for docs

[allcontributors]

@peterschutt

I've put up a pull request to add @JorenSix! 🎉