Add chain_completable to Event and Future to connect different trees

Author: pitr-ch

lib/concurrent/edge/future.rb

@@ -223,6 +223,12 @@ def chain(executor = nil, &callback)
 
       alias_method :then, :chain
 
+      def chain_completable(completable_event)
+        on_completion! { completable_event.complete_with COMPLETED }
+      end
+
+      alias_method :tangle, :chain_completable
+
       # Zip with future producing new Future
       # @return [Event]
       def zip(other)
@@ -606,6 +612,12 @@ def then_ask(actor)
         self.then { |v| actor.ask(v) }.flat
       end
 
+      def chain_completable(completable_future)
+        on_completion! { completable_future.complete_with internal_state }
+      end
+
+      alias_method :tangle, :chain_completable
+
       # @yield [reason] executed only on parent failure
       # @return [Future]
       def rescue(executor = nil, &callback)

spec/concurrent/edge/future_spec.rb

@@ -3,6 +3,23 @@
 
 describe 'Concurrent::Edge futures' do
 
+  describe 'chain_completable' do
+    it 'event' do
+      b = Concurrent.event
+      a = Concurrent.event.chain_completable(b)
+      a.complete
+      expect(b).to be_completed
+    end
+
+    it 'future' do
+      b = Concurrent.future
+      a = Concurrent.future.chain_completable(b)
+      a.success :val
+      expect(b).to be_completed
+      expect(b.value).to eq :val
+    end
+  end
+
   describe '.post' do
     it 'executes tasks asynchronously' do
       queue = Queue.new