Description

See#17732.

This draft PR integratessass-parser into Prettier for Sass parsing (and presumably could be expanded to include CSS parsing as well). For ease of initial testing, this first draft adds a newsassparser parsing language, and leaves the existingscss parser intact. Sass tests are modified to run against the new parser, so that test failures highlight formatting differences:

yarn test tests/format/scss/

There are currently a lot of test failures. Many of them should hopefully be resolved with fixes/additions to the underlying Sass parser, but some of them represent possible formatting improvements, and/or edge cases that still need to be addressed.

Todo

• sass-parser isn't production-ready, and is still missing some critical features. Many of these are documented with// TODO comments in the new parser, including:
  • selector parsing is not yet implemented
  • nodes are missingraws data
  • declaration.important throws an error
  • configuration nodes are missingsource.span (throws an error)
  • should@extend nodes expose a parsedselector?
• In addition, some Prettier-specific features have also not yet been implemented in this PR
  • @prettier-placeholder (see alsoProposal: refactor css placeholder for TemplateLiteral #6790)
  • using the new parser for CSS as well

Checklist

• I’ve added tests to confirm my change works.
• (If changing the API or CLI) I’ve documented the changes I’ve made (in thedocs/ directory).
• (If the change is user-facing) I’ve added my changes tochangelog_unreleased/*/XXXX.md file followingchangelog_unreleased/TEMPLATE.md.
• I’ve read thecontributing guidelines.