Add a sorter based on a TailwindCSS output file

This sorter will use the same definition sequence found in the output
file which is what is also used by the official TailwindCSS prettyprint
formatter.

Co-Authored-By: Francesco Aiello <francesco.aiello@hey.com>

.gitignore

@@ -7,3 +7,4 @@
 /spec/reports/
 /tmp/
 /Gemfile.lock
+/test/fixtures/tailwindcss/class_sorting.css

erb-formatter.gemspec

@@ -30,5 +30,6 @@ Gem::Specification.new do |spec|
 
   spec.add_dependency "syntax_tree", '~> 6.0'
 
+  spec.add_development_dependency "tailwindcss-rails", "~> 2.0"
   spec.add_development_dependency "m", "~> 1.0"
 end

lib/erb/formatter/command_line.rb

@@ -3,6 +3,19 @@
 require 'optparse'
 
 class ERB::Formatter::CommandLine
+  def self.tailwindcss_class_sorter(css_path)
+    css = File.read(css_path)
+
+    css = css.tr("\n", " ").gsub(%r{\/\*.*?\*\/},"") # remove comments
+    css = css.gsub(%r<@media.*?\{>, "") # strip media queries
+    css = css.scan(%r<(?:^|\}|\{) *(\S.*?) *\{>).join(" ") # extract selectors
+    classes = css.tr(","," ").split(" ").grep(/\./).uniq.map { _1.split('.').last.gsub("\\", "") }
+    indexed_classes = Hash[classes.zip((0...classes.size).to_a)]
+
+    ->(class_name) do
+      indexed_classes[class_name] || classes.index { _1.start_with?(class_name) } || -1
+    end
+  end
 
   attr_reader :write, :filename, :read_stdin
 
@@ -41,6 +54,10 @@ def initialize(argv, stdin: $stdin)
         @single_class_per_line = value
       end
 
+      parser.on("--tailwind-output-path PATH", "Set the path to the tailwind output file") do |value|
+        @tailwind_output_path = value
+      end
+
       parser.on("--[no-]debug", "Enable debug mode") do |value|
         $DEBUG = value
       end
@@ -73,11 +90,21 @@ def run
       end
     end
 
+    if @tailwind_output_path
+      css_class_sorter = self.class.tailwindcss_class_sorter(@tailwind_output_path)
+    end
+
     files.each do |(filename, code)|
       if ignore_list.should_ignore_file? filename
         print code unless write
       else
-        html = ERB::Formatter.new(code, filename: filename, line_width: @width || 80, single_class_per_line: @single_class_per_line)
+        html = ERB::Formatter.new(
+          code,
+          filename: filename,
+          line_width: @width || 80,
+          single_class_per_line: @single_class_per_line,
+          css_class_sorter: css_class_sorter
+        )
 
         if write
           File.write(filename, html)

test/erb/test_formatter.rb

@@ -16,7 +16,7 @@ def test_fixtures
       expected_path = erb_path.chomp('.erb') + '.expected.erb'
 
       # File.write expected_path, ERB::Formatter.format(File.read(erb_path))
-      assert_equal(File.read(expected_path), ERB::Formatter.format(File.read(erb_path)), "Formatting of #{erb_path} failed")
+      assert_equal(File.read(expected_path), ERB::Formatter.new(File.read(erb_path)).to_s, "Formatting of #{erb_path} failed")
     end
   end
 
@@ -156,4 +156,29 @@ def test_format_ruby_with_long_lines_and_larger_line_width
       ).to_s,
     )
   end
+
+  def test_tailwindcss_class_sorting
+    require 'tailwindcss-rails'
+    require 'erb/formatter/command_line'
+
+    error_log = "#{__dir__}/../../tmp/tailwindcss.err.log"
+    Dir.mkdir(File.dirname(error_log)) unless File.exist?(File.dirname(error_log))
+
+    system(
+      Tailwindcss::Commands.executable,
+      "--content", "#{__dir__}/../fixtures/tailwindcss/class_sorting.html.erb",
+      "--output", "#{__dir__}/../fixtures/tailwindcss/class_sorting.css",
+      err: error_log,
+    ) || raise("Failed to generate tailwindcss output:\n#{File.read(error_log)}")
+
+    css_class_sorter = ERB::Formatter::CommandLine.tailwindcss_class_sorter("#{__dir__}/../fixtures/tailwindcss/class_sorting.css")
+
+    assert_equal(
+      File.read("#{__dir__}/../fixtures/tailwindcss/class_sorting.html.expected.erb"),
+      ERB::Formatter.new(
+        File.read("#{__dir__}/../fixtures/tailwindcss/class_sorting.html.erb"),
+        css_class_sorter: css_class_sorter,
+      ).to_s,
+    )
+  end
 end

test/fixtures/tailwindcss/class_sorting.html.erb

@@ -0,0 +1,14 @@
+<div class="pt-2 p-4">
+</div>
+
+<div class="text-gray-700 shadow-md p-3 border-gray-300 ml-4 h-24 flex border-2">
+</div>
+
+<div class="hover:opacity-75 opacity-50 hover:scale-150 scale-125">
+</div>
+
+<div class="lg:grid-cols-4 grid sm:grid-cols-3 grid-cols-2">
+</div>
+
+<div class="p-3 shadow-xl select2-dropdown">
+</div>

test/fixtures/tailwindcss/class_sorting.html.expected.erb

@@ -0,0 +1,16 @@
+<div class="p-4 pt-2">
+</div>
+
+<div
+  class="ml-4 flex h-24 border-2 border-gray-300 p-3 text-gray-700 shadow-md"
+>
+</div>
+
+<div class="scale-125 opacity-50 hover:scale-150 hover:opacity-75">
+</div>
+
+<div class="grid grid-cols-2 sm:grid-cols-3 lg:grid-cols-4">
+</div>
+
+<div class="select2-dropdown p-3 shadow-xl">
+</div>