If an app failed to start because of a LoadError, then correctly relo…

…ad RubyGems caches so that newly installed gems can be found.

lib/passenger/application.rb

@@ -52,7 +52,7 @@ def self.detect_framework_version(app_root)
 			# If this error was reported before, then the cache might be out of
 			# date because the Rails version may have been installed now.
 			# So we reload the cache and try again.
-			Gem.cache.refresh!
+			Gem.refresh_all_caches!
 			found_version = Gem.cache.search('rails', gem_version_spec).map do |x|
 				x.version.version
 			end.sort.last

lib/passenger/framework_spawner.rb

@@ -253,6 +253,10 @@ def preload_rails
 	end
 
 	def handle_spawn_application(app_root, lower_privilege, lowest_user)
+		if @refresh_gems_cache
+			Gem.refresh_all_caches!
+			@refresh_gems_cache = false
+		end
 		lower_privilege = lower_privilege == "true"
 		@spawners_lock.synchronize do
 			spawner = @spawners[app_root]
@@ -263,6 +267,14 @@ def handle_spawn_application(app_root, lower_privilege, lowest_user)
 				rescue ArgumentError, AppInitError, ApplicationSpawner::Error => e
 					client.write('exception')
 					client.write_scalar(marshal_exception(e))
+					if e.child_exception.is_a?(LoadError)
+						# A source file failed to load, maybe because of a
+						# missing gem. If that's the case then the sysadmin
+						# will install probably the gem. So next time an app
+						# is launched, we'll refresh the RubyGems cache so
+						# that we can detect new gems.
+						@refresh_gems_cache = true
+					end
 					return
 				end
 				@spawners[app_root] = spawner

lib/passenger/spawn_manager.rb

@@ -120,6 +120,10 @@ def cleanup
 	def handle_spawn_application(app_root, lower_privilege, lowest_user)
 		lower_privilege = lower_privilege == "true"
 		app = nil
+		if @refresh_gems_cache
+			Gem.refresh_all_caches!
+			@refresh_gems_cache = false
+		end
 		begin
 			app = spawn_application(app_root, lower_privilege, lowest_user)
 		rescue ArgumentError => e
@@ -133,6 +137,15 @@ def handle_spawn_application(app_root, lower_privilege, lowest_user)
 			   (e.child_exception.is_a?(UnknownError) && e.child_exception.real_class_name =~ /^ActiveRecord/)
 				send_error_page(client, 'database_error', :error => e,
 					:app_root => app_root)
+			elsif e.child_exception.is_a?(LoadError) ||
+			   (e.child_exception.is_a?(UnknownError) && e.child_exception.real_class_name == "MissingSourceFile")
+				# A source file failed to load, maybe because of a
+				# missing gem. If that's the case then the sysadmin
+				# will install probably the gem. So next time an app
+				# is launched, we'll refresh the RubyGems cache so
+				# that we can detect new gems.
+				@refresh_gems_cache = true
+				send_error_page(client, 'load_error', :error => e, :app_root => app_root)
 			else
 				send_error_page(client, 'app_init_error', :error => e,
 					:app_root => app_root)

lib/passenger/templates/load_error.html.erb

@@ -0,0 +1,46 @@
+<% layout 'error_layout', :title => "Ruby on Rails application could not be started" do %>
+<h1 class="error_title">Ruby on Rails application could not be started</h1>
+<div id="content">
+
+	A source file that the application requires, is missing.
+	<ul>
+	<li class="first">
+		<div class="container">
+		<div class="content">
+		It is possible that you didn't upload your application files correctly.
+		Please check whether all your application files are uploaded.
+		</div>
+		</div>
+	</li>
+	<li class="last">
+		<div class="container">
+		<div class="content">
+		A required library may not installed. Please install all libraries
+		that this application requires.
+		</div>
+		</div>
+	</li>
+	</ul>
+	Further information about the error may have been written to the
+	application's log file. Please check it in order to analyse the problem.
+
+	<dl>
+	<dt>Error message:</dt>
+	<dd><%=h @error.child_exception.message %></dd>
+
+	<dt>Exception class:</dt>
+	<dd><%=h @error.child_exception.class %></dd>
+
+	<dt>Application root:</dt>
+	<dd>
+		<tt class="filename"><%=h @app_root %></tt>
+	</dd>
+
+	<dt>Backtrace:</dt>
+	<dd>
+		<%= backtrace_html_for(@error.child_exception) %>
+	</dd>
+	</dl>
+
+</div>
+<% end %>

lib/passenger/utils.rb

@@ -194,6 +194,17 @@ def recv_io
 	end
 end
 
+module Gem
+	# Refresh all RubyGems caches so that newly installed gems can be found.
+	def self.refresh_all_caches!
+		# Why doesn't RubyGems already provide an API for this?
+		cache.refresh!
+		MUTEX.synchronize do
+			@searcher = nil
+		end
+	end
+end
+
 module GC
 	if !respond_to?(:copy_on_write_friendly?)
 		# Checks whether the current Ruby interpreter's garbage