Replay previous events to new subscribers

lib/cucumber/core/event_bus.rb

@@ -15,6 +15,7 @@ class EventBus
       def initialize(registry = Events.registry)
         @event_types = registry.freeze
         @handlers = {}
+        @event_queue = []
       end
 
       # Register for an event. The handler proc will be called back with each of the attributes
@@ -24,12 +25,14 @@ def on(event_id, handler_object = nil, &handler_proc)
         validate_handler_and_event_id!(handler, event_id)
         event_class = event_types[event_id]
         handlers_for(event_class) << handler
+        broadcast_queued_events_to handler, event_class
       end
 
       # Broadcast an event
       def broadcast(event)
         raise ArgumentError, "Event type #{event.class} is not registered. Try one of these:\n#{event_types.values.join("\n")}" unless is_registered_type?(event.class)
         handlers_for(event.class).each { |handler| handler.call(event) }
+        @event_queue << event
       end
 
       def method_missing(event_id, *args)
@@ -41,6 +44,14 @@ def method_missing(event_id, *args)
 
       private
 
+      def broadcast_queued_events_to(handler, event_type)
+        @event_queue.select { |event|
+          event.class == event_type
+        }.each { |event|
+          handler.call(event)
+        }
+      end
+
       def handlers_for(event_class)
         @handlers[event_class.to_s] ||= []
       end

spec/cucumber/core/event_bus_spec.rb

@@ -136,6 +136,18 @@ def on_test_event(event)
           expect(handler.received_payload.some_attribute).to eq :some_attribute
         end
 
+        it "sends events that were broadcast before you subscribed" do
+          event_bus.test_event :some_attribute
+          event_bus.another_test_event
+
+          received_payload = nil
+          event_bus.on(:test_event) do |event|
+            received_payload = event
+          end
+
+          expect(received_payload.some_attribute).to eq(:some_attribute)
+        end
+
       end
 
       it "will let you inspect the registry" do