Script to normalize Slim template class names into their attribute form. This more regular form works better with Tailwind, both the parser and the sorting formatters.

normalize_slim_class_names.rb

#!/usr/bin/env ruby

class SlimLine
  KNOWN_TAGS = "div|header|footer|aside|section|article|nav|main|ul|ol|li|a|p|h1|h2|h3|h4|h5|h6|span|button|form|input|textarea|select|option|label|fieldset|legend|table|thead|tbody|tr|td|th"
  RE = %r{^(?<whitespace>\s*)(?<tag>(#{KNOWN_TAGS})\b)?(?<id>#[a-z\-]+)?(?<class_list>(\.[-a-z][a-z0-9\-:\/]*)+)?(?<rest>.*)?}

  def initialize(line)
    @line = line.dup
  end

  attr_reader :line

  def convert
    line.rstrip!

    return line unless match = RE.match(@line)
    return line if !match[:tag] && !match[:id] && !match[:class_list]
    return line if match[:rest]&.start_with?(":")

    tag = match[:tag] || "div"
    return line unless KNOWN_TAGS.include?(tag)

    str = match[:whitespace] || ""
    str << tag

    if match[:class_list]
      classes = match[:class_list]
        .split(".")
        .map(&:strip)
        .reject(&:empty?)
    else
      classes = []
    end

    rest = (match[:rest] || "").strip

    if rest.match?(/^\[[^\]]*$/)
      # starting [ but no ending ]
      str << "["
      rest.gsub!(/^\[(.*)/, "\\1")
    else
      str << " "
      rest.gsub!(/^(\[(.*)\])/, "\\2")
    end

    # attributes with =
    re = /([a-z0-9@\-\.:]+)\s?=\s?["']([^'"]*)["']/

    attrs = rest.scan(re).each_with_object({}) do |(k, v), h|
      h[k] = v
    end

    rest.gsub!(re, "")

    # attributes without =
    re = /(data-|x-)[:a-z0-9\-]+/
    attrs.merge!(
      rest.scan(re).each_with_object(attrs) do |k, h|
        h[$&] = ""
      end
    )

    rest.gsub!(re, "")

    attrs["id"] = match[:id].gsub("#", "") if match[:id]

    if classes.any?
      attrs["class"] = classes.concat((attrs["class"] || "").split(" ")).uniq.join(" ")
    end

    if attrs.any?
      str << attrs.sort.map { |k, v| "#{k}=\"#{v}\"" }.join(" ")
      str.rstrip!
    end

    str.rstrip!
    str << " " + rest.strip unless rest.empty?

    str.rstrip
  end
end

class SlimFile
  def initialize(path)
    @path = path
  end

  def convert
    File
      .readlines(@path)
      .map do |line|
        SlimLine
          .new(line)
          .convert
      end
      .join("\n")
  end
end

def main
  paths = Dir.glob("app/**/*.html.slim")
  paths.each do |path|
    slim = SlimFile.new(path)
    converted = slim.convert
    File.write(path, converted)
  end
end

if defined?(RSpec)
  RSpec.describe SlimLine do
    def self.ex(line, expected)
      it(line.inspect + " => " + expected.inspect) { expect(SlimLine.new(line).convert).to(eq(expected)) }
    end

    ex(".foo.bar", "div class=\"foo bar\"")
    ex(".-m-1.bar", "div class=\"-m-1 bar\"")
    ex(".p-1.border-border", "div class=\"p-1 border-border\"")
    ex(".grid.lg:grid-cols-2", "div class=\"grid lg:grid-cols-2\"")
    ex(".lg:pr-16.lg:w-1/4", "div class=\"lg:pr-16 lg:w-1/4\"")
    ex(".foo.bar Content", "div class=\"foo bar\" Content")
    ex(".foo.bar= variable", "div class=\"foo bar\" = variable")
    ex("header.foo.bar", "header class=\"foo bar\"")
    ex("header.foo.bar[data-thing]", "header class=\"foo bar\" data-thing=\"\"")
    ex("header.foo.bar[data-thing=\"1 2 long\"]", "header class=\"foo bar\" data-thing=\"1 2 long\"")
    ex("    footer.foo.bar[data-thing=\"1 2 long\"]", "    footer class=\"foo bar\" data-thing=\"1 2 long\"")
    ex(".foo[data-controller=\"thing\"", "div[class=\"foo\" data-controller=\"thing\"")
    ex("input.ph0[", "input[class=\"ph0\"")
    ex("#foo", "div id=\"foo\"")
    ex("#foo.bar", "div class=\"bar\" id=\"foo\"")
    ex(".foo[class=\"thing\"]", "div class=\"foo thing\"")
    ex("div.hi[class=\"foo-[666]\"]", "div class=\"hi foo-[666]\"")
    ex(".foo[class=\"foo\"]", "div class=\"foo\"")
    ex("- if true", "- if true")
    ex("= @title", "= @title")
    ex("", "")
    ex("div= @title", "div = @title")
    ex("pattern=\"abc\"", "pattern=\"abc\"")
    ex("button.btn[@click.prevent = \"fn()\"]= var", "button @click.prevent=\"fn()\" class=\"btn\" = var")
    ex("h1 class=\"bg-red-500\" Admin", "h1 class=\"bg-red-500\" Admin")
    ex("button.btn[@click.prevent = \"fn()\"]= t('.omg')", "button @click.prevent=\"fn()\" class=\"btn\" = t('.omg')")
    ex("  label: t(\"omg\")", "  label: t(\"omg\")")
    ex("#top-nav.relative[data-turbo-permanent]", "div class=\"relative\" data-turbo-permanent=\"\" id=\"top-nav\"")
  end
end

if __FILE__ == $PROGRAM_NAME
  main
end