Use ServerProcess class

lib/tailwindcss-rails.rb

@@ -5,3 +5,4 @@ module Tailwindcss
 require_relative "tailwindcss/version"
 require_relative "tailwindcss/engine"
 require_relative "tailwindcss/commands"
+require_relative "tailwindcss/server_process"

lib/tailwindcss/engine.rb

@@ -15,16 +15,7 @@ class Engine < ::Rails::Engine
     end
 
     server do
-      tailwind_pid = fork do
-        # To avoid stealing keystrokes from the debug gem's IRB console in the main process (which
-        # needs to be able to read from $stdin), we use `IO.open(..., 'r+')`.
-        IO.popen(Tailwindcss::Commands.watch_command, 'r+') do |io|
-          IO.copy_stream(io, $stdout)
-        end
-      end
-      at_exit do
-        Process.kill(:INT, tailwind_pid)
-      end
+      ServerProcess.start
     end
   end
 end

lib/tailwindcss/server_process.rb

@@ -0,0 +1,99 @@
+module Tailwindcss
+  class ServerProcess
+    attr_reader :server, :pid
+
+    def self.start
+      new.start
+    end
+
+    def start
+      @server = Server.new(self)
+      @pid = fork do
+        monitor_server
+        exit_hook
+        # Using IO.popen(command, 'r+') will avoid watch_command read from $stdin.
+        # If we use system(*command) instead, IRB and Debug can't read from $stdin
+        # correctly bacause some keystrokes will be taken by watch_command.
+        IO.popen(Commands.watch_command, 'r+') do |io|
+          IO.copy_stream(io, $stdout)
+        end
+      end
+      Process.detach pid
+
+      server.monitor_process
+      server.exit_hook
+    end
+
+    def stop
+      return if dead?
+
+      Process.kill(:INT, pid)
+      Process.wait(pid)
+    rescue Errno::ECHILD, Errno::ESRCH
+    end
+
+    def dead?
+      Process.wait(pid, Process::WNOHANG)
+      false
+    rescue Errno::ECHILD, Errno::ESRCH
+      true
+    end
+
+    private
+
+    def monitor_server
+      Thread.new do
+        loop do
+          if server.dead?
+            puts "Tailwind detected server has gone away"
+            exit
+          end
+          sleep 2
+        end
+      end
+    end
+
+    def exit_hook
+      at_exit do
+        puts "Stopping tailwind..."
+        server.stop
+      end
+    end
+
+    class Server
+      attr_reader :process, :pid
+
+      def initialize(process)
+        @process = process
+        @pid = Process.pid
+      end
+
+      def monitor_process
+        Thread.new do
+          loop do
+            if process.dead?
+              puts "Detected tailwind has gone away, stopping server..."
+              exit
+            end
+            sleep 2
+          end
+        end
+      end
+
+      def exit_hook
+        at_exit do
+          process.stop
+        end
+      end
+
+      def dead?
+        Process.ppid != pid
+      end
+
+      def stop
+        Process.kill(:INT, pid)
+      rescue Errno::ECHILD, Errno::ESRCH
+      end
+    end
+  end
+end