Prevent infinite boot loop

e3cd7e4 introduced the possibility of
an infinite boot loop, where we try to restart the server, but it
doesn't resolve the version mismatch (for whatever reason), so we try
again...

Related to #479

Author: jonleighton

CHANGELOG.md

@@ -4,6 +4,8 @@
   (#478)
 * Time out after 10 seconds if starting the spring server doesn't work
   (maybe related to #480, #479)
+* Prevent infinite boot loop when trying to restart the spring server
+  due to client/server version mismatch (related to #479)
 
 ## 1.7.0
 

lib/spring/client/run.rb

@@ -13,7 +13,9 @@ class Run < Command
 
       def initialize(args)
         super
-        @signal_queue = []
+
+        @signal_queue  = []
+        @server_booted = false
       end
 
       def log(message)
@@ -74,6 +76,8 @@ def boot_server
         pid     = Process.spawn(gem_env, env.server_command, out: File::NULL)
         timeout = Time.now + BOOT_TIMEOUT
 
+        @server_booted = true
+
         until env.socket_path.exist?
           _, status = Process.waitpid2(pid, Process::WNOHANG)
 
@@ -89,6 +93,10 @@ def boot_server
         end
       end
 
+      def server_booted?
+        @server_booted
+      end
+
       def gem_env
         bundle = Bundler.bundle_path.to_s
         paths  = Gem.path + ENV["GEM_PATH"].to_s.split(File::PATH_SEPARATOR)
@@ -108,13 +116,17 @@ def stop_server
       def verify_server_version
         server_version = server.gets.chomp
         if server_version != env.version
-          $stderr.puts <<-ERROR
-There is a version mismatch between the spring client (#{env.version}) and the server (#{server_version}).
-Restarting to resolve.
-ERROR
+          $stderr.puts "There is a version mismatch between the spring client " \
+                         "(#{env.version}) and the server (#{server_version})."
 
-          stop_server
-          cold_run
+          if server_booted?
+            $stderr.puts "We already tried to reboot the server, but the mismatch is still present."
+            exit 1
+          else
+            $stderr.puts "Restarting to resolve."
+            stop_server
+            cold_run
+          end
         end
       end