Suspend and Resume on TSTP and CONT signals rails#361

ctrl-z (SIGTSTP) doesn't work with Spring, and it corrupts the terminal

as mentioned by @casper in Issue rails#361:
> the spring server is somehow attached to the PTY of the shell

the solution is to:
> trap SIGTSTP and tell the server to disengage from the PTY
> before the client process is suspended

CHANGELOG.md

@@ -3,6 +3,7 @@
 * Fix binstubs not being replaced when their quoting style was changed (#534)
 * Preserve comments right after the shebang line which might include magic comments such as `frozen_string_literal: true'
 * Fix binstub failures when Bundler's `BUNDLE_APP_CONFIG` environment variable is present (#545)
+* Properly suspend and resume on ctrl-z TSTP and CONT (#361)
 
 ## 2.0.2
 

lib/spring/client/run.rb

@@ -161,6 +161,8 @@ def run_command(client, application)
         if pid && !pid.empty?
           log "got pid: #{pid}"
 
+          suspend_resume_on_tstp_cont(pid)
+
           forward_signals(application)
           status = application.read.to_i
 
@@ -181,6 +183,18 @@ def queue_signals
         end
       end
 
+      def suspend_resume_on_tstp_cont(pid)
+        trap("TSTP") {
+          log "suspended"
+          Process.kill("STOP", pid.to_i)
+          Process.kill("STOP", Process.pid)
+        }
+        trap("CONT") {
+          log "resumed"
+          Process.kill("CONT", pid.to_i)
+        }
+      end
+
       def forward_signals(application)
         @signal_queue.each { |sig| kill sig, application }