Always subscribe to event objects via `AS::Notifications.subscribe`

We don't need to have a special subscribe method for objects.  The
regular `subscribe` method is more expensive than a specialized method,
but `subscribe` should not be called frequently.  If that turns out to
be a hotspot, we can introduce a specialized method.  :)

2 files changed, 9 insertions, 12 deletions

diff --git a/activesupport/lib/active_support/notifications/fanout.rb b/activesupport/lib/active_support/notifications/fanout.rb
index 91d8491c7e..2fd683a1de 100644
--- a/activesupport/lib/active_support/notifications/fanout.rb
+++ b/activesupport/lib/active_support/notifications/fanout.rb
@@ -27,15 +27,6 @@ module ActiveSupport
         subscriber
       end
 
-      def subscribe_event(pattern = nil, &block)
-        subscriber = Subscribers.event_object_subscriber pattern, block
-        synchronize do
-          @subscribers << subscriber
-          @listeners_for.clear
-        end
-        subscriber
-      end
-
       def unsubscribe(subscriber_or_name)
         synchronize do
           case subscriber_or_name
@@ -80,12 +71,16 @@ module ActiveSupport
       module Subscribers # :nodoc:
         def self.new(pattern, listener)
           if listener.respond_to?(:start) && listener.respond_to?(:finish)
-            subscriber = Evented.new pattern, listener
+            subscriber_class = Evented
           else
-            subscriber = Timed.new pattern, listener
+            if listener.respond_to?(:arity) && listener.arity == 1
+              subscriber_class = EventObject
+            else
+              subscriber_class = Timed
+            end
           end
 
-          wrap_all pattern, subscriber
+          wrap_all pattern, subscriber_class.new(pattern, listener)
         end
 
         def self.event_object_subscriber(pattern, block)
diff --git a/activesupport/lib/active_support/notifications/instrumenter.rb b/activesupport/lib/active_support/notifications/instrumenter.rb
index 72e5064679..455b7a44a6 100644
--- a/activesupport/lib/active_support/notifications/instrumenter.rb
+++ b/activesupport/lib/active_support/notifications/instrumenter.rb
@@ -69,12 +69,14 @@ module ActiveSupport
         @allocation_count_finish = 0
       end
 
+      # Record information at the time this event starts
       def start!
         @time = now
         @cpu_time_start = now_cpu
         @allocation_count_start = now_allocations
       end
 
+      # Record information at the time this event finishes
       def finish!
         @cpu_time_finish = now_cpu
         @end = now