fix(carousel): disable transition until animation completes

- Force the carousel indicator to not select the slide if the animation has not completed
- Factor out `goNext` function to not redefine on each execution of `select`

chore(carousel): move `$currentTransition` check to `select` method

Fixes angular-ui#3729
Closes angular-ui#3757

src/carousel/carousel.js

@@ -22,28 +22,33 @@ angular.module('ui.bootstrap.carousel', [])
     if (direction === undefined) {
       direction = nextIndex > self.getCurrentIndex() ? 'next' : 'prev';
     }
-    if (nextSlide && nextSlide !== self.currentSlide) {
-      goNext();
+    //Prevent this user-triggered transition from occurring if there is already one in progress
+    if (nextSlide && nextSlide !== self.currentSlide && !$scope.$currentTransition) {
+      goNext(nextSlide, nextIndex, direction);
     }
-    function goNext() {
-      // Scope has been destroyed, stop here.
-      if (destroyed) { return; }
+  };
 
-      angular.extend(nextSlide, {direction: direction, active: true});
-      angular.extend(self.currentSlide || {}, {direction: direction, active: false});
-      if ($animate.enabled() && !$scope.noTransition && nextSlide.$element) {
-        $scope.$currentTransition = true;
-        nextSlide.$element.one('$animate:close', function closeFn() {
-          $scope.$currentTransition = null;
-        });
-      }
+  function goNext(slide, index, direction) {
+    // Scope has been destroyed, stop here.
+    if (destroyed) { return; }
 
-      self.currentSlide = nextSlide;
-      currentIndex = nextIndex;
-      //every time you change slides, reset the timer
-      restartTimer();
+    angular.extend(slide, {direction: direction, active: true});
+    angular.extend(self.currentSlide || {}, {direction: direction, active: false});
+    if ($animate.enabled() && !$scope.noTransition && !$scope.$currentTransition &&
+      slide.$element) {
+      $scope.$currentTransition = true;
+      slide.$element.one('$animate:close', function closeFn() {
+        $scope.$currentTransition = null;
+      });
     }
-  };
+
+    self.currentSlide = slide;
+    currentIndex = index;
+
+    //every time you change slides, reset the timer
+    restartTimer();
+  }
+
   $scope.$on('$destroy', function () {
     destroyed = true;
   });
@@ -75,19 +80,13 @@ angular.module('ui.bootstrap.carousel', [])
   $scope.next = function() {
     var newIndex = (self.getCurrentIndex() + 1) % slides.length;
 
-    //Prevent this user-triggered transition from occurring if there is already one in progress
-    if (!$scope.$currentTransition) {
-      return self.select(getSlideByIndex(newIndex), 'next');
-    }
+    return self.select(getSlideByIndex(newIndex), 'next');
   };
 
   $scope.prev = function() {
     var newIndex = self.getCurrentIndex() - 1 < 0 ? slides.length - 1 : self.getCurrentIndex() - 1;
 
-    //Prevent this user-triggered transition from occurring if there is already one in progress
-    if (!$scope.$currentTransition) {
-      return self.select(getSlideByIndex(newIndex), 'prev');
-    }
+    return self.select(getSlideByIndex(newIndex), 'prev');
   };
 
   $scope.isActive = function(slide) {