CLI subcommand for non-JS class sorting

[aptinio]

The design system knows how to sort classes, but there's no way to access that outside JavaScript. The Prettier plugin uses the sorting API directly — non-JS tools have to reimplement sorting by parsing compiled CSS output instead.

A CLI subcommand would close that gap:

tailwindcss sort-classes [--input input.css] [--cwd dir]

$ echo "py-3 p-1 px-3" | tailwindcss sort-classes
p-1 px-3 py-3

It loads the design system once, then reads class lists from stdin and writes sorted results to stdout, one per line, until stdin closes. Sorting semantics match the Prettier plugin: unknown classes stay at the front in their original order, known classes sort by canonical position, and duplicate known classes are removed.

This would benefit ecosystems the Prettier plugin doesn't reach — Elixir/HEEx, Ruby/ERB, Go templates, Python/Jinja2 — as well as editor plugins that don't want a Node.js dependency (e.g. a Neovim plugin using treesitter to find class attributes).

I'm building tw_sort, an Elixir library that sorts Tailwind classes in HEEx templates via mix format. It currently parses CSS output to determine ordering. I'd be happy to contribute a working implementation — I have one on a fork with unit and integration tests.

[aptinio]

I went looking for who else might benefit from this and found the same pattern across ecosystems: tools either re-implement the sort order and drift from it, or depend on Node.js/Prettier in ecosystems that don't otherwise use them.

A few examples:

• Elixir — tailwind_formatter is blocked on v4 support (100phlecs/tailwind_formatter#60) since resolveConfig was removed
• Ruby — Herb's Tailwind sorting rewriter uses an extracted JS package, so it can't work in tailwindcss-rails projects that have no Node runtime (marcoroth/herb#858)
• Go — templ's templ fmt doesn't sort Tailwind classes (a-h/templ#1263)
• Rust — Rustywind has an open PR trying to match the Prettier sort order; Biome has an open issue too
• Python — djLint, the main Django/Jinja formatter, has no Tailwind sorting; the Prettier plugin can't handle Jinja2
• PHP — No pure-PHP Tailwind sorting exists; Laravel Pint, PHP-CS-Fixer, and PHP_CodeSniffer have no support for it
• Editors — Outside VS Code, Tailwind class sorting either requires Node.js (tailwind-sorter.nvim) or isn't available at all

The implementation is small — a readline loop around the existing design system.