Change implementation due to review comments

README.md

@@ -406,6 +406,14 @@ If you have Rails Engines in your application that use Tailwind CSS, they will b
 
 - The engine must have `tailwindcss-rails` as gem dependency.
 - The engine must have a `app/assets/tailwind/<engine_name>/application.css` file or your application must have overridden file in the same location of your application root.
+- The engine must register itself in Tailwindcss Rails:
+```ruby
+  initializer 'your_engine.tailwindcss' do |app|
+    ActiveSupport.on_load(:tailwindcss_rails) do
+      config.tailwindcss_rails.engines << Your::Engine.engine_name
+    end
+  end
+```
 
 ## Troubleshooting
 

lib/tailwindcss/commands.rb

@@ -3,13 +3,16 @@
 module Tailwindcss
   module Commands
     class << self
-      def compile_command(debug: false, **kwargs)
+      def rails_root
+        defined?(Rails) ? Rails.root : Pathname.new(Dir.pwd)
+      end
+
+      def compile_command(input = rails_root.join("app/assets/tailwind/application.css").to_s, debug: false, **kwargs)
         debug = ENV["TAILWINDCSS_DEBUG"].present? if ENV.key?("TAILWINDCSS_DEBUG")
-        rails_root = defined?(Rails) ? Rails.root : Pathname.new(Dir.pwd)
 
         command = [
           Tailwindcss::Ruby.executable(**kwargs),
-          "-i", rails_root.join("app/assets/tailwind/application.css").to_s,
+          "-i", input,
           "-o", rails_root.join("app/assets/builds/tailwind.css").to_s,
         ]
 
@@ -21,8 +24,8 @@ def compile_command(debug: false, **kwargs)
         command
       end
 
-      def watch_command(always: false, poll: false, **kwargs)
-        compile_command(**kwargs).tap do |command|
+      def watch_command(input = rails_root.join("app/assets/tailwind/application.css").to_s, always: false, poll: false, **kwargs)
+        compile_command(input, **kwargs).tap do |command|
           command << "-w"
           command << "always" if always
           command << "-p" if poll
@@ -39,15 +42,13 @@ def rails_css_compressor?
         defined?(Rails) && Rails&.application&.config&.assets&.css_compressor.present?
       end
 
-      def engines_tailwindcss_roots
+      def engines_roots
         return [] unless defined?(Rails)
+        return [] unless Rails.application&.config&.tailwindcss_rails&.engines
 
-        Rails::Engine.subclasses.select do |engine|
+        Rails::Engine.descendants.select do |engine|
           begin
-            spec = Gem::Specification.find_by_name(engine.engine_name)
-            spec.dependencies.any? { |d| d.name == 'tailwindcss-rails' }
-          rescue Gem::MissingSpecError
-            false
+            engine.engine_name.in?(Rails.application.config.tailwindcss_rails.engines)
           end
         end.map do |engine|
           [
@@ -57,19 +58,17 @@ def engines_tailwindcss_roots
         end.compact
       end
 
-      def enhance_command(command)
-        engine_roots = Tailwindcss::Commands.engines_tailwindcss_roots
+      def with_dynamic_input
+        engine_roots = Tailwindcss::Commands.engines_roots
         if engine_roots.any?
           Tempfile.create('tailwind.css') do |file|
             file.write(engine_roots.map { |root| "@import \"#{root}\";" }.join("\n"))
             file.write("\n@import \"#{Rails.root.join('app/assets/tailwind/application.css')}\";\n")
             file.rewind
-            transformed_command = command.dup
-            transformed_command[2] = file.path
-            yield transformed_command if block_given?
+            yield file.path if block_given?
           end
         else
-          yield command if block_given?
+          yield rails_root.join("app/assets/tailwind/application.css").to_s if block_given?
         end
       end
     end

lib/tailwindcss/engine.rb

@@ -2,6 +2,13 @@
 
 module Tailwindcss
   class Engine < ::Rails::Engine
+    config.tailwindcss_rails = ActiveSupport::OrderedOptions.new
+    config.tailwindcss_rails.engines = []
+
+    initializer 'tailwindcss.load_hook' do |app|
+      ActiveSupport.run_load_hooks(:tailwindcss_rails, app)
+    end
+
     initializer "tailwindcss.disable_generator_stylesheets" do
       Rails.application.config.generators.stylesheets = false
     end

lib/tasks/build.rake

@@ -4,8 +4,8 @@ namespace :tailwindcss do
     debug = args.extras.include?("debug")
     verbose = args.extras.include?("verbose")
 
-    command = Tailwindcss::Commands.compile_command(debug: debug)
-    Tailwindcss::Commands.enhance_command(command) do |transformed_command|
+    Tailwindcss::Commands.with_dynamic_input do |input|
+      command = Tailwindcss::Commands.compile_command(input, debug: debug)
       env = Tailwindcss::Commands.command_env(verbose: verbose)
       puts "Running: #{Shellwords.join(command)}" if verbose
 
@@ -20,8 +20,8 @@ namespace :tailwindcss do
     always = args.extras.include?("always")
     verbose = args.extras.include?("verbose")
 
-    command = Tailwindcss::Commands.watch_command(always: always, debug: debug, poll: poll)
-    Tailwindcss::Commands.enhance_command(command) do |transformed_command|
+    Tailwindcss::Commands.with_dynamic_input do |input|
+      command = Tailwindcss::Commands.watch_command(input, always: always, debug: debug, poll: poll)
       env = Tailwindcss::Commands.command_env(verbose: verbose)
       puts "Running: #{Shellwords.join(command)}" if verbose