## Summary
Implement support for RDJson output for `ruff check`, as requested in
#8655.
## Test Plan
Tested using a snapshot test. Same approach as for e.g. the JSON output
formatter.
## Additional info
I tried to keep the implementation close to the JSON implementation.
I had to deviate a bit to make the `suggestions` key work: If there are
no suggestions, then setting `suggestions` to `null` is invalid
according to the JSONSchema. Therefore, I opted for a slightly more
complex implementation, that skips the `suggestions` key entirely if
there are no fixes available for the given diagnostic. Maybe it would
have been easier to set `"suggestions": []`, but I ended up doing it
this way.
I didn't consider notebooks, as I _think_ that RDJson doesn't work with
notebooks. This should be confirmed, and if so, there should be some
form of warning or error emitted when trying to output diagnostics for a
notebook.
I also didn't consider `ruff format`, as this comment:
https://github.com/astral-sh/ruff/issues/8655#issuecomment-1811446160
suggests that that wouldn't be compatible.
I'm new to Rust, any feedback is appreciated. 🙂 I
implemented this in order to have a productive rainy saturday afternoon,
I'm not knowledgeable about RDJson beyond the sources linked in the
issue.
0ea2519e80