refactor(ng-repeat): refactor fix for dart-archive#1015

Author: vicb

lib/directive/ng_repeat.dart

@@ -132,17 +132,23 @@ class NgRepeat {
     _watch = _scope.watch(
         _listExpr,
         (CollectionChangeRecord changes, _) {
-          _onChange((changes is CollectionChangeRecord) ? changes : null);
+          if (changes is CollectionChangeRecord) {
+            _onCollectionChange(changes);
+          } else if (_rows != null) {
+            _rows.forEach((row) {
+               row.scope.destroy();
+               _viewPort.remove(row.view);
+             });
+          }
         },
         collection: true,
         formatters: formatters
     );
   }
 
   // Computes and executes DOM changes when the item list changes
-  void _onChange(CollectionChangeRecord changes) {
-    final iterable = (changes == null) ? const [] : changes.iterable;
-    final int length = (changes == null) ? 0 : changes.length;
+  void _onCollectionChange(CollectionChangeRecord changes) {
+    final int length = changes.length;
     final rows = new List<_Row>(length);
     final changeFunctions = new List<Function>(length);
     final removedIndexes = <int>[];
@@ -170,51 +176,43 @@ class NgRepeat {
       _rows = new List<_Row>(length);
       for (var i = 0; i < length; i++) {
         changeFunctions[i] = (index, previousView) {
-          addRow(index, iterable.elementAt(i), previousView);
+          addRow(index, changes.iterable.elementAt(i), previousView);
         };
       }
     } else {
-      if (changes == null) {
-        _rows.forEach((row) {
-          row.scope.destroy();
-          _viewPort.remove(row.view);
-        });
-        leftInDom.clear();
-      } else {
-        changes.forEachRemoval((CollectionChangeItem removal) {
-          var index = removal.previousIndex;
-          var row = _rows[index];
-          row.scope.destroy();
-          _viewPort.remove(row.view);
-          leftInDom.removeAt(domLength - 1 - index);
-        });
+      changes.forEachRemoval((CollectionChangeItem removal) {
+        var index = removal.previousIndex;
+        var row = _rows[index];
+        row.scope.destroy();
+        _viewPort.remove(row.view);
+        leftInDom.removeAt(domLength - 1 - index);
+      });
 
-        changes.forEachAddition((CollectionChangeItem addition) {
-          changeFunctions[addition.currentIndex] = (index, previousView) {
-            addRow(index, addition.item, previousView);
-          };
-        });
+      changes.forEachAddition((CollectionChangeItem addition) {
+        changeFunctions[addition.currentIndex] = (index, previousView) {
+          addRow(index, addition.item, previousView);
+        };
+      });
 
-        changes.forEachMove((CollectionChangeItem move) {
-          var previousIndex = move.previousIndex;
-          var value = move.item;
-          changeFunctions[move.currentIndex] = (index, previousView) {
-            var previousRow = _rows[previousIndex];
-            var childScope = previousRow.scope;
-            var childContext = _updateContext(childScope.context, index, length);
-            if (!identical(childScope.context[_valueIdentifier], value)) {
-              childContext[_valueIdentifier] = value;
-            }
-            rows[index] = _rows[previousIndex];
-            // Only move the DOM node when required
-            if (domIndex < 0 || leftInDom[domIndex] != previousIndex) {
-              _viewPort.move(previousRow.view, moveAfter: previousView);
-              leftInDom.remove(previousIndex);
-            }
-            domIndex--;
-          };
-        });
-      }
+      changes.forEachMove((CollectionChangeItem move) {
+        var previousIndex = move.previousIndex;
+        var value = move.item;
+        changeFunctions[move.currentIndex] = (index, previousView) {
+          var previousRow = _rows[previousIndex];
+          var childScope = previousRow.scope;
+          var childContext = _updateContext(childScope.context, index, length);
+          if (!identical(childScope.context[_valueIdentifier], value)) {
+            childContext[_valueIdentifier] = value;
+          }
+          rows[index] = _rows[previousIndex];
+          // Only move the DOM node when required
+          if (domIndex < 0 || leftInDom[domIndex] != previousIndex) {
+            _viewPort.move(previousRow.view, moveAfter: previousView);
+            leftInDom.remove(previousIndex);
+          }
+          domIndex--;
+        };
+      });
     }
 
     var previousView = null;