MemberSelector UnitTests

src/Markup/Avalonia.Markup.Xaml/Templates/MemberSelector.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
 using Avalonia.Controls.Templates;
+using Avalonia.Data;
 using Avalonia.Markup.Data;
 using System;
 
@@ -25,6 +26,11 @@ namespace Avalonia.Markup.Xaml.Templates
 
         public object Select(object o)
         {
+            if (string.IsNullOrEmpty(MemberName))
+            {
+                return o;
+            }
+
             if (_expressionNode == null)
             {
                 _expressionNode = ExpressionNodeBuilder.Build(MemberName);
@@ -37,7 +43,18 @@ namespace Avalonia.Markup.Xaml.Templates
 
             _expressionNode.Target = new WeakReference(o);
 
-            return _memberValueNode.CurrentValue.Target;
+            object result = _memberValueNode.CurrentValue.Target;
+
+            if (result == AvaloniaProperty.UnsetValue)
+            {
+                return null;
+            }
+            else if (result is BindingError)
+            {
+                return null;
+            }
+
+            return result;
         }
 
         private ExpressionNode _expressionNode;

tests/Avalonia.Markup.Xaml.UnitTests/Avalonia.Markup.Xaml.UnitTests.csproj

@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <Project ToolsVersion="4.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <Import Project="..\..\packages\xunit.runner.visualstudio.2.1.0\build\net20\xunit.runner.visualstudio.props" Condition="Exists('..\..\packages\xunit.runner.visualstudio.2.1.0\build\net20\xunit.runner.visualstudio.props')" />
   <PropertyGroup>
@@ -103,6 +103,7 @@
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="SampleAvaloniaObject.cs" />
     <Compile Include="StyleTests.cs" />
+    <Compile Include="Templates\MemberSelectorTests.cs" />
     <Compile Include="Templates\DataTemplateTests.cs" />
     <Compile Include="Xaml\BasicTests.cs" />
     <Compile Include="Xaml\ControlBindingTests.cs" />

tests/Avalonia.Markup.Xaml.UnitTests/Templates/MemberSelectorTests.cs

@@ -0,0 +1,168 @@
+// Copyright (c) The Avalonia Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using Avalonia.Markup.Xaml.Templates;
+using System;
+using Xunit;
+
+namespace Avalonia.Markup.Xaml.UnitTests.Templates
+{
+    public class MemberSelectorTests
+    {
+        [Fact]
+        public void Should_Not_Hold_Reference_To_Object()
+        {
+            WeakReference dataRef = null;
+
+            var selector = new MemberSelector() { MemberName = "Child.StringValue" };
+
+            Action run = () =>
+            {
+                var data = new Item()
+                {
+                    Child = new Item() { StringValue = "Value1" }
+                };
+
+                Assert.Same("Value1", selector.Select(data));
+
+                dataRef = new WeakReference(data);
+            };
+
+            run();
+
+            GC.Collect();
+
+            Assert.False(dataRef.IsAlive);
+        }
+
+        [Fact]
+        public void Should_Select_Child_Property_Value()
+        {
+            var selector = new MemberSelector() { MemberName = "Child.StringValue" };
+
+            var data = new Item()
+            {
+                Child = new Item() { StringValue = "Value1" }
+            };
+
+            Assert.Same("Value1", selector.Select(data));
+        }
+
+        [Fact]
+        public void Should_Select_Child_Property_Value_In_Multiple_Items()
+        {
+            var selector = new MemberSelector() { MemberName = "Child.StringValue" };
+
+            var data = new Item[]
+            {
+                new Item() { Child = new Item() { StringValue = "Value1" } },
+                new Item() { Child = new Item() { StringValue = "Value2" } },
+                new Item() { Child = new Item() { StringValue = "Value3" } }
+            };
+
+            Assert.Same("Value1", selector.Select(data[0]));
+            Assert.Same("Value2", selector.Select(data[1]));
+            Assert.Same("Value3", selector.Select(data[2]));
+        }
+
+        [Fact]
+        public void Should_Select_MoreComplex_Property_Value()
+        {
+            var selector = new MemberSelector() { MemberName = "Child.Child.Child.StringValue" };
+
+            var data = new Item()
+            {
+                Child = new Item()
+                {
+                    Child = new Item()
+                    {
+                        Child = new Item() { StringValue = "Value1" }
+                    }
+                }
+            };
+
+            Assert.Same("Value1", selector.Select(data));
+        }
+
+        [Fact]
+        public void Should_Select_Null_Value_On_Null_Object()
+        {
+            var selector = new MemberSelector() { MemberName = "StringValue" };
+
+            Assert.Equal(null, selector.Select(null));
+        }
+
+        [Fact]
+        public void Should_Select_Null_Value_On_Wrong_MemberName()
+        {
+            var selector = new MemberSelector() { MemberName = "WrongProperty" };
+
+            var data = new Item() { StringValue = "Value1" };
+
+            Assert.Same(null, selector.Select(data));
+        }
+
+        [Fact]
+        public void Should_Select_Simple_Property_Value()
+        {
+            var selector = new MemberSelector() { MemberName = "StringValue" };
+
+            var data = new Item() { StringValue = "Value1" };
+
+            Assert.Same("Value1", selector.Select(data));
+        }
+
+        [Fact]
+        public void Should_Select_Simple_Property_Value_In_Multiple_Items()
+        {
+            var selector = new MemberSelector() { MemberName = "StringValue" };
+
+            var data = new Item[]
+            {
+                new Item() { StringValue = "Value1" },
+                new Item() { StringValue = "Value2" },
+                new Item() { StringValue = "Value3" }
+            };
+
+            Assert.Same("Value1", selector.Select(data[0]));
+            Assert.Same("Value2", selector.Select(data[1]));
+            Assert.Same("Value3", selector.Select(data[2]));
+        }
+
+        [Fact]
+        public void Should_Select_Target_On_Empty_MemberName()
+        {
+            var selector = new MemberSelector();
+
+            var data = new Item() { StringValue = "Value1" };
+
+            Assert.Same(data, selector.Select(data));
+        }
+
+        [Fact]
+        public void Should_Support_Change_Of_MemberName()
+        {
+            var selector = new MemberSelector() { MemberName = "StringValue" };
+
+            var data = new Item()
+            {
+                StringValue = "Value1",
+                IntValue = 1
+            };
+
+            Assert.Same("Value1", selector.Select(data));
+
+            selector.MemberName = "IntValue";
+
+            Assert.Equal(1, selector.Select(data));
+        }
+
+        private class Item
+        {
+            public Item Child { get; set; }
+            public int IntValue { get; set; }
+
+            public string StringValue { get; set; }
+        }
+    }
+}