Consider disabling `require_trailing_commas` lint if language version of file is >= 3.7

[parlough]

It will conflict with tall style formatting.

[FMorschel]

if there is no comma:

• in case the content fits the line, the formatter will choose one line
• else, the formatter will choose what it believes best, which most of the time will be "long style" formatting, without adding any comma.

This would work, and would avoid the problem with the formatter not being able to distinguish hand-inserted commas from formatter-inserted commas. Unfortunately, as far as I can tell, virtually zero users actually want code that looks like this without a trailing comma:

noTrailingComma(
  longArgument,
  anotherLongArgument
);

From all of the hand-formatted Dart code I've seen and from the large number of users who manually opted in to writing trailing commas before this proposal, it seems like almost all users who want the ) on the next line also want a trailing comma after the last argument.

Originally posted by @munificent in dart-lang/dart_style#1253 (comment)

So I'm unsure if removing the lint is what we want, but I'll leave to the team to decide.

[bwilkerson]

... which most of the time will be "long style" formatting, without adding any comma.

The final decision was that the formatter will add or remove trailing commas based on whether or not the list is split across multiple lines. It will not honor the presence or absence of a trailing comma.

That means that this lint is pointless for users that use the formatter. If we have enough users that don't use the formatter then it might make sense to keep this lint, but I, and several others, are hoping that most users will use the new formatter so that this lint is no longer helpful.

[parlough]

I didn't really consider projects not using the formatter, but I suppose that's a potential reason to keep it working with a language version after 3.7.

However, in its docs, the rule says it assumes code is formatted with dart format. So perhaps it's fine to assume that users of the lint wouldn't want it triggering with a 3.7 language version?

[bwilkerson]

That makes sense to me.

[FMorschel]

users of the lint wouldn't want it triggering with a 3.7 language version?

That makes sense to me too.

I'll just note that:

but I, and several others, are hoping that most users will use the new formatter so that this lint is no longer helpful.

It doesn't seem to be the case. If you open the above mentioned issue, it has been less than one day since Dart 3.7 is out and we have five different comments asking for the trailing commas to not get removed.

[bwilkerson]

... but I, and several others, are hoping that most users will use the new formatter ...

Those comments are all related to the behavior of the formatter, which means that they're coming from users that use the formatter. They don't address the question of what percentage of users use the formatter (irrespective of whether or not they like the change).

... so that this lint is no longer helpful.

The lint is no longer useful to users that use the formatter because the formatter no longer honors the use of a trailing comma as a way of deciding how to format the code. It simply formats the code the way it wants and then it adds or removes commas based on the format.

In other words: using the formatter and enabling this lint are mutually exclusive options.

The hope is that there are (or will be) few enough users that enable this lint that it would make sense to retire it.

[FMorschel]

I understand your point now. Thanks!

[srawlins]

CC @pq looking at lints we may no longer want to maintain.

[srawlins]

There's so much activity over at dart-lang/dart_style, I'd strongly consider a cherry-pick to disable require_trailing_commas when lang version is 3.7.