fix preloading of app with hidden pty with lots of output

if we never read from the PTY, and the app spews a lot of messages
on startup, it might hang because the buffer is full

Author: ccutrer

lib/spring/application.rb

@@ -283,6 +283,7 @@ def print_exception(stream, error)
     def with_pty
       PTY.open do |master, slave|
         [STDOUT, STDERR, STDIN].each { |s| s.reopen slave }
+        Thread.new { master.read }
         yield
         reset_streams
       end

lib/spring/test/acceptance_test.rb

@@ -328,6 +328,17 @@ def exec_name
         expr = "p Kernel.private_instance_methods.include?(:raise)"
         assert_success %(bin/rails runner '#{expr}'), stdout: "true"
       end
+
+      test "app gets reloaded even with a ton of boot output" do
+        File.write(app.path("config/initializers/verbose.rb"), "50.times { puts 'x' * 80 }\n")
+        begin
+          app.env["RAILS_ENV"] = "test"
+          assert_success "bin/rails runner 'puts Spring.watcher.class'", stdout: "Polling"
+          assert_app_reloaded
+        ensure
+          File.unlink(app.path("config/initializers/verbose.rb"))
+        end
+      end
     end
   end
 end