Connect a PTY when preloading in background

Readline + libedit gets messed up if it loads when not connected to a
terminal. This resolves that problem.

Fixes #244.

CHANGELOG.md

@@ -3,6 +3,9 @@
 * Fix `$0` so that it is no longer prefixed with "spring ", as doing
   this cause issues with rspec when running just `rspec` with no
   arguments.
+* Ensure we're always connected to a tty when preloading the
+  application in the background, in order to avoid loading issues
+  with readline + libedit which affected pry-rails.
 
 ## 1.1.0
 

lib/spring/application.rb

@@ -1,5 +1,6 @@
 require "spring/boot"
 require "set"
+require "pty"
 
 module Spring
   class Application
@@ -108,6 +109,10 @@ def preload
       end
     end
 
+    def eager_preload
+      with_pty { preload }
+    end
+
     def run
       state :running
       manager.puts
@@ -128,7 +133,7 @@ def serve(client)
       manager.puts
 
       stdout, stderr, stdin = streams = 3.times.map { client.recv_io }
-      [STDOUT, STDERR].zip([stdout, stderr]).each { |a, b| a.reopen(b) }
+      [STDOUT, STDERR, STDIN].zip(streams).each { |a, b| a.reopen(b) }
 
       preload unless preloaded?
 
@@ -144,8 +149,6 @@ def serve(client)
       end
 
       pid = fork {
-        Process.setsid
-        STDIN.reopen(stdin)
         IGNORE_SIGNALS.each { |sig| trap(sig, "DEFAULT") }
         trap("TERM", "DEFAULT")
 
@@ -172,7 +175,7 @@ def serve(client)
       }
 
       disconnect_database
-      [STDOUT, STDERR].each { |stream| stream.reopen(spring_env.log_file) }
+      reset_streams
 
       log "forked #{pid}"
       manager.puts pid
@@ -273,5 +276,18 @@ def print_exception(stream, error)
       stream.puts("#{first}: #{error} (#{error.class})")
       rest.each { |line| stream.puts("\tfrom #{line}") }
     end
+
+    def with_pty
+      PTY.open do |master, slave|
+        [STDOUT, STDERR, STDIN].each { |s| s.reopen slave }
+        yield
+        reset_streams
+      end
+    end
+
+    def reset_streams
+      [STDOUT, STDERR].each { |stream| stream.reopen(spring_env.log_file) }
+      STDIN.reopen("/dev/null")
+    end
   end
 end

lib/spring/application/boot.rb

@@ -1,3 +1,6 @@
+# This is necessary for the terminal to work correctly when we reopen stdin.
+Process.setsid
+
 require "spring/application"
 
 app = Spring::Application.new(
@@ -6,11 +9,10 @@
 )
 
 Signal.trap("TERM") { app.terminate }
-Signal.trap("TTOU", "IGNORE")
 
 Spring::ProcessTitleUpdater.run { |distance|
   "spring app    | #{app.app_name} | started #{distance} ago | #{app.app_env} mode"
 }
 
-app.preload if ENV.delete("SPRING_PRELOAD") == "1"
+app.eager_preload if ENV.delete("SPRING_PRELOAD") == "1"
 app.run