Deprecate stylistic rules handled by Prettier

[jeddy3]

We should deprecate that stylistic rules that we froze a year ago.

Even though deprecating is a non-breaking change, we should do this as part of a major release so that we can communicate this significant change in direction.

We'd release a new version of our standard config that removes the deprecated rules. Therefore, most of our users will never see the deprecation warnings.

As such, we won't need to prepare a plugin pack of the stylistic rules. If people want to continue using the stylistic rules, they can port the rules they need to a plugin under their own namespace and outside of the Stylelint organisation.

Ref: #6311 (comment)
Ref: #5674

[ybiquitous]

@jeddy3 Thanks for opening the issue. I agree with the deprecation included in a major release. 👍🏼

[jeddy3]

Following on from #6483, let's only deprecate the rules handled by Prettier as suggested by @ybiquitous in #6311 (comment).

The 8 rules not handled by Prettier are unlikely to be added to it as they need configuration options to be safe or desired.

They are also not as problematic as some of our other stylistic rules as they:

• don't have the possibility of introducing new lint problems
• use the construct parsers rather than stylesearch
• cleanly work with the AST, either mutating raws or single nodes

We can move these rules to 3 subgroups within our "Enforce non-stylistic conventions" group:

• Case
• Empty lines
• Whitespace inside

We can then rename the:

• "Enforce non-stylistic conventions" group to "Enforce conventions"
• "Enforce stylistic conventions" group to "Deprecated" (before being removed entirely in v16)

I believe this approach will strike the best balance between our needs to:

• ensure the smoothest migration to v15 for the majority of our users
• move forward with plans like migrating to ESM (so that we can update a bunch of our dependencies)

[ybiquitous]

@jeddy3 More balanced idea! 👍🏼

[Mouvedia]

before being removed entirely in v16

Alright, so that means the plugin won't be needed for a while.

[jeddy3]

It'll give people time to, if needed, write community plugins for the rules that we deprecate. The rules in #6483 won't be deprecated, so there won't be a need for us or anyone else to write a plugin for them.

[jeddy3]

Closed by #6504

[Mouvedia]

I wanted to check whether all the rules that were being deprecated were properly covered by prettier.

This one has options:

• "always"
• "always-single-line"
• "never-single-line"
• "always-multi-line"
• "never-multi-line"

Are all of these properly covered by prettier? If not, we need to make a list of rules that are being deprecated but are only partially covered by the prettier replacement. e.g.

name	support	note
rule A	full
rule B	partial	does not support option X and Y
rule C	partial	only support option Z

I think this should be documented before the version 16 release.