A fork of the original CSSLint Build v0.10.0 15-August-2013 01:07:22, heavily modified since then as a part of Stylus extension, now extracted to a separate repo.

• Supports modern CSS syntax including nesting, grids, complex selectors in pseudo selectors like :has().
• Verifies function arguments including the modern color-mix(), hwb(), etc.
• Partly rewritten and mostly refactored to use modern JS.
• Small minified size: ~80kB parser with all the CSS specs and grammar, ~26kB rule checker.
• Somewhat optimized for speed: ~2x faster than stylelint with a dozen of simple rules and up to 10x in the subsequent runs while editing the CSS in the browser thanks to a primitive cache that reuses results from the previous run.
• New rules:
  • known-pseudos: require known :pseudo or ::pseudo selector
  • shorthand-overrides: require a shorthand to precede an individual property
  • simple-not: require a simple selector in :not()
  • selector-newline: warn if descendant selector is on a new line
  • style-rule-nesting: warn if CSS nesting is used
• No support for CLI or extra formatters.

WIP:

• Get CSS specs from MDN or csstree or W3C. Doesn't seem entirely straightforward so far: there are mistakes/omissions in some definitions.

TODO:

• Make the embedded /* csslint */ comments work with caching.
• Update the old CSSLint rules and remove the obsolete ones.
• Adopt the most popular/useful rules from other linters.
• Check validity of calc() and other math functions.
• Restore the JSDoc comments from the original CSSLint?