Handle .stopImmediatePropagation() being called on command events

spec/command-registry-spec.coffee

@@ -67,3 +67,13 @@ describe "CommandRegistry", ->
 
     grandchild.dispatchEvent(new CustomEvent('command', bubbles: true))
     expect(calls).toEqual ['child-1', 'child-2']
+
+  it "stops invoking callbacks when .stopImmediatePropagation() is called on the event", ->
+    calls = []
+
+    registry.add 'command', '.parent', -> calls.push('parent')
+    registry.add 'command', '.child', -> calls.push('child-2')
+    registry.add 'command', '.child', (event) -> calls.push('child-1'); event.stopImmediatePropagation()
+
+    grandchild.dispatchEvent(new CustomEvent('command', bubbles: true))
+    expect(calls).toEqual ['child-1']

src/command-registry.coffee

@@ -17,12 +17,17 @@ class CommandRegistry
 
   dispatchCommand: (event) =>
     propagationStopped = false
+    immediatePropagationStopped = false
     currentTarget = event.target
 
     syntheticEvent = Object.create event,
       eventPhase: value: Event.BUBBLING_PHASE
       currentTarget: get: -> currentTarget
-      stopPropagation: value: -> propagationStopped = true
+      stopPropagation: value: ->
+        propagationStopped = true
+      stopImmediatePropagation: value: ->
+        propagationStopped = true
+        immediatePropagationStopped = true
 
     loop
       matchingListeners =
@@ -31,6 +36,7 @@ class CommandRegistry
           .sort (a, b) -> a.compare(b)
 
       for listener in matchingListeners
+        break if immediatePropagationStopped
         listener.callback.call(currentTarget, syntheticEvent)
 
       break if propagationStopped