feat(ui): add rich as an opt-in output format

[latiefdole]

Description

Adds rich as a fourth value of the existing OutputFormat enum, alongside csv, table and json. It renders list output as a bordered, colorized table.

This is opt-in only. The default table output is byte-for-byte unchanged, so no existing command, script or piped invocation changes behaviour unless the format is explicitly requested.

Usage

kaggle competitions list --format rich

Or set a persistent default for an interactive shell:

export KAGGLE_OUTPUT_FORMAT=rich

KAGGLE_OUTPUT_FORMAT only applies when neither --csv nor --format is passed; an explicit flag always wins, and unrecognized values fall back to table. Projections work as with the other formats, e.g. --format "rich(ref,reward)".

Dependency

rich is an optional extra, not a runtime dependency:

pip install kaggle[rich]

If --format rich is requested without the package installed, the CLI prints an install hint to stderr and falls back to print_table rather than failing.

Behaviour notes

• Cell values render via rich.text.Text, so API content containing square brackets is never interpreted as console markup.
• Columns use overflow="fold", so long values wrap instead of being truncated.
• Column alignment and the empty-result case match print_table (an empty list prints nothing).

Docs and tests

• Documented in docs/output_format.md next to the existing formats.
• Tests assert on rendered output rather than on mocks.

Testing

• 1268 passed, 0 failed
• black --check . clean
• mypy clean on the changed files

Note

This PR previously also contained unrelated CLI usability fixes. Those have been split out into #1171 so this one stays scoped to the output format.

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[latiefdole]

@googlebot I signed it!

[stevemessick]

/gcbrun

[stevemessick]

@latiefdole Looks like you need to update the formatting of three files.

Just to be clear, we have not yet decided if we want this feature, but are considering it.

[stevemessick]

After taking a close look at this PR we have found a number of problems:

1. Introduces behavioral regressions.
2. Causes failure of automated checks.
3. Fails unit tests.
4. Adds dead code.
5. Doesn't follow repro coding practices.
6. Provides no escape mechanism to obtain legacy formatting (contrary to claims).

[latiefdole]

Thanks for the detailed review - all six points were correct, and I've reworked the PR rather than patching around them.

I want to specifically own the worst one: the claim that output fell back to plain text when piped was false. There was no isatty() check anywhere in the code, and since rich was a hard dependency the RICH_AVAILABLE guard was always true, so piped output still got box borders. I documented behaviour I had not implemented or verified. That's on me.

Design change: instead of intercepting print_table, rich is now a fourth value of the existing OutputFormat enum (csv/table/json/rich), used via --format rich, with KAGGLE_OUTPUT_FORMAT for a persistent default. Nothing renders through rich unless it is explicitly requested. This is what resolves points 1 and 6: the default table output is byte-for-byte unchanged, so there is no legacy formatting to escape back to - plain output is the default, and the escape mechanism is simply not passing the flag.

Point by point:

1. Behavioral regressions - resolved by the opt-in design above. I also fixed the underlying rendering bugs so the rich path itself doesn't lose data: values render via Text() so API content isn't parsed as console markup (previously a[bold]b[/bold]c printed as abc), columns use overflow="fold" instead of truncating with an ellipsis, and column alignment plus the empty-list case now match print_table (an empty list printed a "No data found." panel before; it now prints nothing, as the original did).
2. Automated checks - black --check . is clean (69 files unchanged; 3 files would have been reformatted before). mypy on the changed files is clean; it previously reported 2 errors in ui.py.
3. Unit tests - 1268 pass, 0 fail. Before this rework: 1213 passed, 1 failed. The failing test was one of my own mock-only tests; I replaced that suite with tests that assert on actually-rendered output.
4. Dead code - removed the unused print_info/print_error/print_success helpers.
5. Repo practices - rich is now an optional extra (kaggle[rich]) rather than a hard dependency, and requesting the format without it installed prints an install hint to stderr and falls back to print_table. I also deleted documentation/intro.md (which carried the false piping claim) and documented the format in docs/output_format.md alongside the existing formats, where it belongs.
6. Escape mechanism - covered above.

The branch is rebased onto current main.

On whether you want the feature at all: understood, and no pressure either way. The point of the opt-in design is that it costs nothing in default behaviour if you're undecided - but if you'd rather not carry it, I'm happy to close this. Just say which.

Separately, this PR previously also carried some unrelated CLI usability fixes (error message hints, a --debug flag, examples in --help). Those are independent of the rich work, so I've split them out into #1171 to keep this PR scoped.

[stevemessick]

/gcbrun

[stevemessick]

Almost there! I think the lint dependencies need to be updated to allow the checks to pass:

Step #3 - "lint": src/kaggle/ui.py:20: error: Cannot find implementation or library stub for module named "rich" [import-not-found]

Otherwise, this looks really good and I look forward to getting it merged!

[stevemessick]

Great!

[stevemessick]

/gcbrun