Preserve BUNDLE_GEMFILE and add a test for it

lib/puma/launcher.rb

@@ -277,7 +277,7 @@ def prune_bundler
 
       log '* Pruning Bundler environment'
       home = ENV['GEM_HOME']
-      Bundler.with_clean_env do
+      Bundler.with_original_env do
         ENV['GEM_HOME'] = home
         ENV['PUMA_BUNDLER_PRUNED'] = '1'
         wild = File.expand_path(File.join(puma_lib_dir, "../bin/puma-wild"))

test/rackup/hello-bundler-env.ru

@@ -0,0 +1 @@
+run lambda { |env| [200, {"Content-Type" => "text/plain"}, ["Hello PATH #{ENV["PATH"]}"]] }

test/test_integration.rb

@@ -51,8 +51,8 @@ def server_cmd(argv)
     "#{base} -b tcp://127.0.0.1:#{@tcp_port} #{argv}"
   end
 
-  def server(argv)
-    @server = IO.popen(server_cmd(argv), "r")
+  def server(argv, env = {})
+    @server = IO.popen(env, server_cmd(argv), "r")
 
     wait_for_server_to_boot(@server)
 
@@ -75,8 +75,8 @@ def stop_forked_server(pid)
     Process.wait2(pid)
   end
 
-  def restart_server_and_listen(argv)
-    server(argv)
+  def restart_server_and_listen(argv, env = {})
+    server(argv, env)
     connection = connect
     initial_reply = read_body(connection)
     restart_server(@server, connection)
@@ -239,6 +239,12 @@ def test_restart_closes_keepalive_sockets_workers
     assert_equal "Hello World", new_reply
   end
 
+  def test_restart_with_prune_bundler_keeps_bundler_env
+    initial_reply, new_reply = restart_server_and_listen("-q --prune-bundler test/rackup/hello-bundler-env.ru", "PATH" => "hello-bundler:#{ENV["PATH"]}", "BUNDLER_ORIG_PATH" => nil)
+    assert_match(/Hello PATH.*hello-bundler/, initial_reply)
+    assert_match(/Hello PATH.*hello-bundler/, new_reply)
+  end
+
   def test_sigterm_closes_listeners_on_forked_servers
     skip NO_FORK_MSG unless HAS_FORK
     pid = start_forked_server("-w 2 -q test/rackup/1second.ru")