Fix issue with preceding:: axis in document fragments

test.js

@@ -675,7 +675,27 @@ module.exports = {
         assert.ok(xpath.select1('/book/characters', doc));
 
         assert.equal(xpath.select1('local-name(/book/characters)', doc), 'characters');
+
+        test.done();
+    }
+
+    ,"preceding:: axis works on document fragments": function (test) {
+        var doc = new dom().parseFromString('<n />'),
+            df = doc.createDocumentFragment(),
+            root = doc.createElement('book');
+
+        df.appendChild(root);
+
+        for (var i = 0; i < 10; i += 1) {
+            root.appendChild(doc.createElement('chapter'));
+        }
+
+        var chapter = xpath.select1("book/chapter[5]", df);
+
+        assert.ok(chapter, 'chapter');
 
+        assert.equal(xpath.select("count(preceding::chapter)", chapter), 4);
+
         test.done();
     }
 }

xpath.js

@@ -1663,6 +1663,18 @@ PathExpr.prototype.init = function(filter, filterPreds, locpath) {
 	this.locationPath = locpath;
 };
 
+/**
+ * Returns the topmost node of the tree containing node
+ */
+function findRoot(node) {
+    while (node && node.parentNode) {
+        node = node.parentNode;
+    }
+
+    return node;
+}
+
+
 PathExpr.prototype.evaluate = function(c) {
 	var nodes;
 	var xpc = new XPathContext();
@@ -1910,9 +1922,8 @@ PathExpr.prototype.evaluate = function(c) {
 						if (xpc.virtualRoot != null) {
 							st = [ xpc.virtualRoot ];
 						} else {
-							st = xpc.contextNode.nodeType == 9 /*Node.DOCUMENT_NODE*/
-								? [ xpc.contextNode ]
-								: [ xpc.contextNode.ownerDocument ];
+                            // cannot rely on .ownerDocument because the node may be in a document fragment
+                            st = [findRoot(xpc.contextNode)];
 						}
 						outer: while (st.length > 0) {
 							for (var m = st.pop(); m != null; ) {