Allow CLI selection of a single rule to check.

[wxtim]

Closes #5544

Additionally...

Fix a bug where empty flow.cylc files caused traceback.

To replicate

mkdir ~/cylc-src/foo
touch ~/cylc-src/foo/flow.cylc
cylc lint ~/cylc-src/foo

Check List

• I have read CONTRIBUTING.md and added my name as a Code Contributor.
• Contains logically grouped changes (else tidy your branch by rebase).
• Does not contain off-topic changes (use other PRs for other changes).
• Applied any dependency changes to both setup.cfg (and conda-environment.yml if present).
• Tests are included (or explain why tests are not needed).
• CHANGES.md entry included if this is a change that can affect users
• Cylc-Doc pull request opened if required at cylc/cylc-doc/pull/XXXX.
• If this is a bug fix, PR should be raised against the relevant ?.?.x branch.

[oliver-sanders]

PR title and description don't appear to match?

Does this do both? If so maybe a bugfix changelog entry?

[wxtim]

Does this do both? If so maybe a bugfix changelog entry?

Yes. Sorry - original text not super clear. Have added the changelog entry as suggested.

[oliver-sanders]

This function feels a bit over-complicated for a single use.

I think it should fail type checking as generators are iterables but are not supported by len()?

Not sure if mypy is smart enough to spot that?

[wxtim]

It is over complicated for a single use. I think that this is code we've replicated in a number of places, and may want again in future . The idea is that this function is available for refactoring elsewhere and for future use cases. Probably also needs list truncation logic too.

• config.py, 570, 2584
• platforms.py 700
• rundb 938

You're right about the type hinting though: My local copy of MyPy has certainly picked that up.

[oliver-sanders]

I think this can be simplified to:

checks = {rule: checks[rule] for rule in options.rule}

Which has the advantage of raising an error if a rule does not exist.

Suggested change

	checks = {k: v for k, v in checks.items() if k in options.rule}
	try:
	checks = {rule: checks[rule] for rule in options.rule}
	except KeyError as exc:
	LOG.error(f'No such rule {exc.args[0]}')
	sys.exit(1)

However, it looks like --rule can only accept one rule at present? If so we don't need the dict comprehension.

I feel we should implement this more like --select (ruff/flake8), to allow the selection of rules OR rule sets?

[wxtim]

Rule can apply multiple rules:

cylc lint /var/tmp/cylc-src/mean.marble -R S001 -R S002

I feel we should implement this more like --select (ruff/flake8), to allow the selection of rules OR rule sets?

A legit point - I'll have a poke and see if I can do that without having two CLI args.
Should cut down the amount of code

[oliver-sanders]

So --rule can be one of style or 728.

AND --ruleset can be one of style, 728 or all.

What's the point of --rule?

[oliver-sanders]

The --select / --ignore interface of ruff is a good gauge of how to go about implementing rule selection.

--select=R  # select all Rxxx rules
--select=R001  # select only R001
--select=R --ignore=R001  # select all R other than R001
--select=R001,R002  # select both R001 and R002
--select=ALL  # magic

[wxtim]

AND --ruleset can be one of style, 728 or all.

No - rulest can be any of the items in the parsed checks for both rulesets currently available because

>>> parse_checks(['style', '728'].keys()
DictKeys('S001', 'S002' ... ... 'R999')

Side effect of this is that the safety mechanism (try/except) is completely redundant.

[wxtim]

Redrafting - not a priority

[wxtim]

Roll this into the full refactor of Cylc Lint - probably a good training day activity for Tim