refactor: introduce "code" option to FormatCommand

[alestiago]

Description

The FormatCommand should offer a --code argument, as in FixCommand to apply fixes to specific lint rules instead of using --fix-<non-standard-code> (currently documented as used for non-whitespace changes only).

Additional context

The FormatCommand is being consumed by dartdev, a command-line utility for Dart development (part of the Dart SDK).

The package:dartdev exposes a FixCommand that accepts a code argument. This is very useful, since it allows to explicitly resolve fixes for a specific linter rule.

With FixCommand you can explicitly solve for directives_ordering, by doing:

dart fix --apply --code=directives_ordering # Solves for "directives_ordering"

Note: The directives_ordering code is already well documented in Dart Linter Rules.

However, the FormatCommand presents another solution which brings inconsistency to the overall Developer Experience offered by the command-line utility for Dart development.

dart format . --code=avoid_single_cascade_in_expression_statements # Could not find an option named "code"
dart format . --fix-single-cascade-statements  

Note: there is no documented "single-cascade-statements" rule in the Dart Linter Rules, instead there is "avoid_single_cascade_in_expression_statements".

[munificent]

The --fix support in dart format is pretty old, which mostly explains why its names don't agree with the linter. Instead of updating the names in --fix, I think the better solution that we're working toward (thanks @keertip!) is to make dart fix fast enough for users to use it for all of the things where dart format --fix is currently supported and faster. That will enable us to remove dart format --fix entirely and have one canonical way to apply code fixes: dart fix.

Given that, I think it's unlikely that we'll bother changing the API of FormatCommand, but if it's urgent or important, I'm up for discussing it.

[alestiago]

Thanks @munificent for the quick reply. I'm happy with the suggested better solution. Is there a way I can track the work towards making dart fix fast enough?

[munificent]

I believe @keertip is working on this, or at least was intending to at some point. I'm not sure if she has any tracking issue for it.

[munificent]

I'm not sure of the exact status, but I believe that dart fix has lightweight mode now. We don't have any intention of putting more effort into dart format --fix. It's deprecated and will be removed when we move to the new tall style (#1403). So I'm going to go ahead and close this.