setting output format hides output in ruff check

[kaddkaka]

When running a ruff check --fix-only there is no output about what errors were fixed. This surprised me, I thought it would still print the fixed error since the documentation about --fix-only says "Like fix, but disables reporting on leftover violation. Implies fix."

Maybe supplying --show-fixes will fix it? Yes,

ruff check --fix-only --show-fixes shows the fixed errors, great!

Can we also get this info in json output format? No,

ruff check --fix-only --show-fixes --output-format json print nothing! --output-format junit has the same issue.

Ruff version: 0.7.0

[zanieb]

❯ echo "import b, a" > example.py
❯ ruff check example.py --select I
example.py:1:1: I001 [*] Import block is un-sorted or un-formatted
  |
1 | / import b, a
  |
  = help: Organize imports

Found 1 error.
[*] 1 fixable with the `--fix` option.

❯ ruff check example.py --select I --fix-only
Fixed 1 error.

❯ echo "import b, a" > example.py
❯ ruff check example.py --select I --fix
Found 1 error (1 fixed, 0 remaining).

❯ ruff check example.py --select I --fix-only --output-format json

❯ echo "import b, a" > example.py
❯ ruff check example.py --select I --fix --output-format json
[]%                        

❯ echo "import b, a" > example.py
❯ ruff check example.py --select I --fix --output-format json --show-fixes
[]%                          

❯ echo "import b, a" > example.py
❯ ruff check example.py --select I --fix-only --show-fixes

Fixed 1 error:
- example.py:
    1 × I001 (unsorted-imports)

Fixed 1 error.                                                                                                                                  

I don't think this has to do with --fix-only, i.e., it applies equally to --fix. I think we should improve the JSON output here, though I don't think it should rely on the --show-fixes flag.

[MichaReiser]

I suspect that Ruff throws away the diagnostics after each fix cycle. We would need to preserve them and pass them through to the json emitter. This likely requires some special casing in the CLI because we don't want to emit the diagnostics for all output formats (which makes the experience somewhat inconsistent)