Don't resubmit the whole cart contents for no reason.

There's a couple of places where this was causing a cart update submission where it wasn't needed, eg the items had not actually changed. The conditional here was designed to stop that from happening, but it was actually passing every time (the conditional logic was not actually catching the case it was supposed to).

This is really expensive!

app/assets/javascripts/darkswarm/controllers/shop_variant_controller.js.coffee

@@ -1,9 +1,5 @@
 Darkswarm.controller "ShopVariantCtrl", ($scope, $modal, Cart) ->
-  $scope.$watchGroup [
-    'variant.line_item.quantity',
-    'variant.line_item.max_quantity'
-  ], (new_value, old_value) ->
-    return if old_value[0] == null && new_value[0] == null
+  $scope.updateCart = (line_item) ->
     Cart.adjust($scope.variant.line_item)
 
   $scope.variant.line_item.quantity ||= 0
@@ -44,10 +40,12 @@ Darkswarm.controller "ShopVariantCtrl", ($scope, $modal, Cart) ->
   $scope.add = (quantity) ->
     item = $scope.variant.line_item
     item.quantity = $scope.sanitizedQuantity() + quantity
+    $scope.updateCart(item)
 
   $scope.addMax = (quantity) ->
     item = $scope.variant.line_item
     item.max_quantity = $scope.sanitizedMaxQuantity() + quantity
+    $scope.updateCart(item)
 
   $scope.canAdd = (quantity) ->
     wantedQuantity = $scope.sanitizedQuantity() + quantity

spec/javascripts/unit/darkswarm/controllers/checkout/shop_variant_controller_spec.js.coffee

@@ -1,6 +1,7 @@
 describe "ShopVariantCtrl", ->
   ctrl = null
   scope = null
+  CartMock = null
 
   beforeEach ->
     module 'Darkswarm'
@@ -16,7 +17,10 @@ describe "ShopVariantCtrl", ->
           max_quantity: undefined
         }
       }
-      ctrl = $controller 'ShopVariantCtrl', {$scope: scope, $modal: $modal, Cart: null}
+      CartMock =
+        adjust: ->
+          true
+      ctrl = $controller 'ShopVariantCtrl', {$scope: scope, $modal: $modal, Cart: CartMock}
 
   it "initializes the quantity for shop display", ->
     expect(scope.variant.line_item.quantity).toEqual 0