Fix read-only file system issue (#556)

* Fix read-only file system issue

* Changes due to review

* Restore original formatting

* Changes due to review

* Remove new line

* Clarify "engines" rake task description

---------

Co-authored-by: Mike Dalessio <mike@37signals.com>

Author: bopm

README.md

@@ -392,7 +392,7 @@ If you need to use a custom input or output file, you can run `bundle exec tailw
 
 _This feature is experimental and may change in the future. If you have feedback, please join the [discussion](https://github.com/rails/tailwindcss-rails/discussions/355)._
 
-If you have Rails Engines in your application that use Tailwind CSS and provide an `app/assets/tailwind/<engine_name>/engine.css` file, entry point files will be created for each of them in `app/assets/builds/tailwind/<engine_name>.css` so they can be included in your host application's Tailwind CSS by adding `@import "../builds/tailwind/<engine_name>"` to your `app/assets/tailwind/application.css` file.
+If you have Rails Engines in your application that use Tailwind CSS and provide an `app/assets/tailwind/<engine_name>/engine.css` file, entry point files will be created for each of them in `app/assets/builds/tailwind/<engine_name>.css` on the first build/watch invocation or manual call for `rails tailwindcss:engines` so they can be included in your host application's Tailwind CSS by adding `@import "../builds/tailwind/<engine_name>"` to your `app/assets/tailwind/application.css` file.
 
 > [!IMPORTANT]
 > You must `@import` the engine CSS files in your `app/assets/tailwind/application.css` for the engine to be included in the build. By default, no engine CSS files are imported, and you must opt-in to using the file in your build.

lib/tailwindcss/engine.rb

@@ -15,9 +15,5 @@ class Engine < ::Rails::Engine
     config.app_generators do |g|
       g.template_engine :tailwindcss
     end
-
-    config.after_initialize do
-      Tailwindcss::Engines.bundle
-    end
   end
 end

lib/tasks/build.rake

@@ -1,6 +1,6 @@
 namespace :tailwindcss do
   desc "Build your Tailwind CSS"
-  task build: :environment do |_, args|
+  task build: [:environment, :engines] do |_, args|
     debug = args.extras.include?("debug")
     verbose = args.extras.include?("verbose")
 
@@ -12,7 +12,7 @@ namespace :tailwindcss do
   end
 
   desc "Watch and build your Tailwind CSS on file changes"
-  task watch: :environment do |_, args|
+  task watch: [:environment, :engines] do |_, args|
     debug = args.extras.include?("debug")
     poll = args.extras.include?("poll")
     always = args.extras.include?("always")
@@ -26,6 +26,11 @@ namespace :tailwindcss do
   rescue Interrupt
     puts "Received interrupt, exiting tailwindcss:watch" if args.extras.include?("verbose")
   end
+
+  desc "Create Tailwind CSS entry point files for Rails Engines"
+  task engines: :environment do
+    Tailwindcss::Engines.bundle
+  end
 end
 
 Rake::Task["assets:precompile"].enhance(["tailwindcss:build"])