Fix how document fragments are added on NodeList operations

pkg/third_party/html5lib/lib/dom.dart

 /// A simple tree API that results from parsing html. Intended to be compatible
 /// with dart:html, but right now it resembles the classic JS DOM.
 library dom;
 
 import 'dart:collection';
 import 'package:source_maps/span.dart' show FileSpan;
 
 import 'src/constants.dart';
 import 'src/list_proxy.dart';
 import 'src/token.dart';
@@ skipping 633 matching lines @@
 
   Node _setParent(Node node) {
     // Note: we need to remove the node from its previous parent node, if any,
     // before updating its parent pointer to point at our parent.
     node.remove();
     node.parent = _parent;
     return node;
   }
 
   void add(Node value) {
-    super.add(_setParent(value));
+    if (value is DocumentFragment) {
+      addAll(value.nodes);
+    } else {
+      super.add(_setParent(value));
+    }
   }
 
   void addLast(Node value) => add(value);
 
   void addAll(Iterable<Node> collection) {
     // Note: we need to be careful if collection is another NodeList.
     // In particular:
     //   1. we need to copy the items before updating their parent pointers,
+    //     _flattenDocFragments does a copy internally.
     //   2. we should update parent pointers in reverse order. That way they
     //      are removed from the original NodeList (if any) from the end, which
     //      is faster.
-    var list = (collection is NodeList || collection is! List)
-        ? collection.toList() : collection as List;
+    var list = _flattenDocFragments(collection);
     for (var node in list.reversed) _setParent(node);
     super.addAll(list);
   }
 
   void insert(int index, Node value) {
-    super.insert(index, _setParent(value));
+    if (value is DocumentFragment) {
+      insertAll(index, value.nodes);
+    } else {
+      super.insert(index, _setParent(value));
+    }
   }
 
   Node removeLast() => super.removeLast()..parent = null;
 
   Node removeAt(int i) => super.removeAt(i)..parent = null;
 
   void clear() {
     for (var node in this) node.parent = null;
     super.clear();
   }
 
   void operator []=(int index, Node value) {
-    this[index].parent = null;
-    super[index] = _setParent(value);
+    if (value is DocumentFragment) {
+      removeAt(index);
+      insertAll(index, value.nodes);
+    } else {
+      this[index].parent = null;
+      super[index] = _setParent(value);
+    }
   }
 
   // TODO(jmesserly): These aren't implemented in DOM _NodeListImpl, see
   // http://code.google.com/p/dart/issues/detail?id=5371
   void setRange(int start, int rangeLength, List<Node> from,
                 [int startFrom = 0]) {
     if (from is NodeList) {
       // Note: this is presumed to make a copy
       from = from.sublist(startFrom, startFrom + rangeLength);
     }
     // Note: see comment in [addAll]. We need to be careful about the order of
     // operations if [from] is also a NodeList.
     for (int i = rangeLength - 1; i >= 0; i--) {
-      this[start + i].parent = null;
-      super[start + i] = _setParent(from[startFrom + i]);
+      this[start + i] = from[startFrom + i];
     }
   }
 
   void replaceRange(int start, int end, Iterable<Node> newContents) {
     removeRange(start, end);
     insertAll(start, newContents);
   }
 
   void removeRange(int start, int rangeLength) {
     for (int i = start; i < rangeLength; i++) this[i].parent = null;
     super.removeRange(start, rangeLength);
   }
 
   void removeWhere(bool test(Element e)) {
     for (var node in where(test)) {
       node.parent = null;
     }
     super.removeWhere(test);
   }
 
   void retainWhere(bool test(Element e)) {
     for (var node in where((n) => !test(n))) {
       node.parent = null;
     }
     super.retainWhere(test);
   }
 
-  void insertAll(int index, List<Node> nodes) {
-    for (var node in nodes) _setParent(node);
-    super.insertAll(index, nodes);
+  void insertAll(int index, Iterable<Node> collection) {
+    // Note: we need to be careful how we copy nodes. See note in addAll.
+    var list = _flattenDocFragments(collection);
+    for (var node in list.reversed) _setParent(node);
+    super.insertAll(index, list);
+  }
+
+  _flattenDocFragments(Iterable<Node> collection) {
+    // Note: this function serves two purposes:
+    //  * it flattens document fragments
+    //  * it creates a copy of [collections] when `collection is NodeList`.
+    var result = [];
+    for (var node in collection) {
+      if (node is DocumentFragment) {
+        result.addAll(node.nodes);
+      } else {
+        result.add(node);
+      }
+    }
+    return result;
   }
 }
 
 
 /// An indexable collection of a node's descendants in the document tree,
 /// filtered so that only elements are in the collection.
 // TODO(jmesserly): this was copied from dart:html
 // TODO(jmesserly): "implements List<Element>" is a workaround for analyzer bug.
 class FilteredElementList extends IterableBase<Element> with ListMixin<Element>
     implements List<Element> {
@@ skipping 184 matching lines @@
 
 class _ConcatTextVisitor extends TreeVisitor {
   final _str = new StringBuffer();
 
   String toString() => _str.toString();
 
   visitText(Text node) {
     _str.write(node.data);
   }
 }