Add blank Context#on_event method

to be able to add custom code invocation on events
like `:terminated`, `:resumed`, `anError`

Author: pitr-ch

lib/concurrent/actor/behaviour.rb

@@ -2,7 +2,6 @@ module Concurrent
   module Actor
 
     # TODO document dependencies
-    # TODO callbacks to context
     module Behaviour
       MESSAGE_PROCESSED = Object.new
 

lib/concurrent/actor/behaviour/executes_context.rb

@@ -5,6 +5,11 @@ class ExecutesContext < Abstract
         def on_envelope(envelope)
           context.on_envelope envelope
         end
+
+        def on_event(event)
+          context.on_event(event)
+          super event
+        end
       end
     end
   end

lib/concurrent/actor/context.rb

@@ -28,6 +28,10 @@ def on_message(message)
         raise NotImplementedError
       end
 
+      # override to add custom code invocation on events like `:terminated`, `:resumed`, `anError`.
+      def on_event(event)
+      end
+
       # @api private
       def on_envelope(envelope)
         @envelope = envelope