Fix MoveToParent for Attr.

Author: denis-ivanov

src/AngleSharp.XPath.Tests/HtmlDocumentNavigatorTests.cs

@@ -3,6 +3,7 @@
 using AngleSharp.Html.Parser;
 using NUnit.Framework;
 using System.Threading.Tasks;
+using System.Xml.XPath;
 using AngleSharp.Dom;
 
 namespace AngleSharp.XPath.Tests
@@ -146,5 +147,31 @@ public void TestNameXPathFunctionOnHTMLDoc()
             // Assert
             Assert.AreEqual(TagNames.Html, htmlNav.Evaluate("name()"));
         }
+
+        [Test]
+        public void MoveToParent_CallWhenCurrentNodeIsAttr_ShouldBeMovedToAttrOwnerElement()
+        {
+            // Arrange
+            var xml = @"<root att1='value 1' att2='value 2'><child>foo</child></root>";
+            var parser = new XmlParser();
+            var doc = parser.ParseDocument(xml);
+            var nav = doc.CreateNavigator(false);
+            nav.MoveToChild("root", "");
+
+            // Act
+
+            if (nav.MoveToFirstAttribute())
+            {
+                do
+                {
+                    Assert.AreEqual(nav.NodeType, XPathNodeType.Attribute);
+                }
+                while (nav.MoveToNextAttribute());
+                nav.MoveToParent();
+            }
+
+            // Assert
+            Assert.AreEqual(nav.Name, "root");
+        }
     }
 }

src/AngleSharp.XPath/AngleSharp.XPath.csproj

@@ -1,8 +1,8 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <Version>2.0.0-alpha-2</Version>
+    <Version>2.0.0-alpha-3</Version>
     <AssemblyVersion>2.0.0</AssemblyVersion>
-    <FileVersion>2.0.0-alpha-2</FileVersion>
+    <FileVersion>2.0.0-alpha-3</FileVersion>
     <Authors>Denis Ivanov</Authors>
     <PackageId>AngleSharp.XPath</PackageId>
     <AssemblyName>AngleSharp.XPath</AssemblyName>

src/AngleSharp.XPath/HtmlDocumentNavigator.cs

@@ -293,11 +293,16 @@ public override bool MoveToNextAttribute()
                 return false;
             }
 
+            if (attr.OwnerElement == null)
+            {
+                return false;
+            }
+
             var attrIndex = attr.OwnerElement.Attributes.Index(attr);
 
 			if (attrIndex >= CurrentElement.Attributes.Length - 1)
 			{
-				return false;
+                return false;
 			}
 
             _currentNode = attr.OwnerElement.Attributes[attrIndex + 1];
@@ -313,6 +318,12 @@ public override bool MoveToNextNamespace(XPathNamespaceScope namespaceScope)
         /// <inheritdoc />
         public override bool MoveToParent()
 		{
+            if (CurrentNode is IAttr attr)
+            {
+                _currentNode = attr.OwnerElement;
+                return true;
+            }
+
 			if (_currentNode.Parent == null)
 			{
 				return false;