4 files changed, 33 insertions, 5 deletions
diff --git a/actionpack/lib/action_controller/metal/helpers.rb b/actionpack/lib/action_controller/metal/helpers.rb
index 35facd13c8..243fd40a7e 100644
--- a/actionpack/lib/action_controller/metal/helpers.rb
+++ b/actionpack/lib/action_controller/metal/helpers.rb
@@ -94,7 +94,6 @@ module ActionController
           extract = /^#{Regexp.quote(_path.to_s)}\/?(.*)_helper.rb$/
           names = Dir["#{_path}/**/*_helper.rb"].map { |file| file.sub(extract, '\1') }
           names.sort!
-          names
         end
         helpers.uniq!
         helpers
diff --git a/actionpack/lib/action_controller/metal/live.rb b/actionpack/lib/action_controller/metal/live.rb
index fb664a69dd..8092fd639f 100644
--- a/actionpack/lib/action_controller/metal/live.rb
+++ b/actionpack/lib/action_controller/metal/live.rb
@@ -34,6 +34,7 @@ module ActionController
   module Live
     class Buffer < ActionDispatch::Response::Buffer #:nodoc:
       def initialize(response)
+        @error_callback = nil
         super(response, SizedQueue.new(10))
       end
 
@@ -56,6 +57,14 @@ module ActionController
         super
         @buf.push nil
       end
+
+      def on_error(&block)
+        @error_callback = block
+      end
+
+      def call_on_error
+        @error_callback.call
+      end
     end
 
     class Response < ActionDispatch::Response #:nodoc: all
@@ -121,6 +130,16 @@ module ActionController
 
         begin
           super(name)
+        rescue => e
+          begin
+            @_response.stream.write(ActionView::Base.streaming_completion_on_exception) if request.format == :html
+            @_response.stream.call_on_error
+          rescue => exception
+            log_error(exception)
+          ensure
+            log_error(e)
+            @_response.stream.close
+          end
         ensure
           @_response.commit!
         end
@@ -129,6 +148,16 @@ module ActionController
       @_response.await_commit
     end
 
+    def log_error(exception)
+      logger = ActionController::Base.logger
+      return unless logger
+
+      message = "\n#{exception.class} (#{exception.message}):\n"
+      message << exception.annoted_source_code.to_s if exception.respond_to?(:annoted_source_code)
+      message << "  " << exception.backtrace.join("\n  ")
+      logger.fatal("#{message}\n\n")
+    end
+
     def response_body=(body)
       super
       response.stream.close if response
diff --git a/actionpack/lib/action_controller/metal/rendering.rb b/actionpack/lib/action_controller/metal/rendering.rb
index c5e7d4e357..bea6b88f91 100644
--- a/actionpack/lib/action_controller/metal/rendering.rb
+++ b/actionpack/lib/action_controller/metal/rendering.rb
@@ -6,7 +6,7 @@ module ActionController
 
     # Before processing, set the request formats in current controller formats.
     def process_action(*) #:nodoc:
-      self.formats = request.formats.map { |x| x.ref }
+      self.formats = request.formats.map(&:ref).compact
       super
     end
 
diff --git a/actionpack/lib/action_controller/test_case.rb b/actionpack/lib/action_controller/test_case.rb
index b9a5e78fe9..a35a613158 100644
--- a/actionpack/lib/action_controller/test_case.rb
+++ b/actionpack/lib/action_controller/test_case.rb
@@ -18,7 +18,7 @@ module ActionController
       @_layouts = Hash.new(0)
       @_files = Hash.new(0)
 
-      ActiveSupport::Notifications.subscribe("render_template.action_view") do |name, start, finish, id, payload|
+      ActiveSupport::Notifications.subscribe("render_template.action_view") do |_name, _start, _finish, _id, payload|
         path = payload[:layout]
         if path
           @_layouts[path] += 1
@@ -28,7 +28,7 @@ module ActionController
         end
       end
 
-      ActiveSupport::Notifications.subscribe("!render_template.action_view") do |name, start, finish, id, payload|
+      ActiveSupport::Notifications.subscribe("!render_template.action_view") do |_name, _start, _finish, _id, payload|
         path = payload[:virtual_path]
         next unless path
         partial = path =~ /^.*\/_[^\/]*$/
@@ -41,7 +41,7 @@ module ActionController
         @_templates[path] += 1
       end
 
-      ActiveSupport::Notifications.subscribe("!render_template.action_view") do |name, start, finish, id, payload|
+      ActiveSupport::Notifications.subscribe("!render_template.action_view") do |_name, _start, _finish, _id, payload|
         next if payload[:virtual_path] # files don't have virtual path
 
         path = payload[:identifier]