Merge pull request #6246 from AvaloniaUI/fixes/4392-compiledbinding-dot-path

Fix "." (empty) paths with compiled bindings.

src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlBindingPathParser.cs

@@ -9,7 +9,6 @@ using XamlX.Ast;
 using XamlX.Transform;
 using XamlX.Transform.Transformers;
 using XamlX.TypeSystem;
-
 using XamlParseException = XamlX.XamlParseException;
 
 namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
@@ -21,6 +20,7 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
             if (node is XamlAstObjectNode binding && binding.Type.GetClrType().Equals(context.GetAvaloniaTypes().CompiledBindingExtension))
             {
                 var convertedNode = ConvertLongFormPropertiesToBindingExpressionNode(context, binding);
+                var foundPath = false;
 
                 if (binding.Arguments.Count > 0 && binding.Arguments[0] is XamlAstTextNode bindingPathText)
                 {
@@ -32,9 +32,18 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
                         nodes.Insert(nodes.TakeWhile(x => x is BindingExpressionGrammar.ITransformNode).Count(), convertedNode);
                     }
 
-                    binding.Arguments[0] = new ParsedBindingPathNode(bindingPathText, context.GetAvaloniaTypes().CompiledBindingPath, nodes);
+                    if (nodes.Count == 1 && nodes[0] is BindingExpressionGrammar.EmptyExpressionNode)
+                    {
+                        binding.Arguments.RemoveAt(0);
+                    }
+                    else
+                    {
+                        binding.Arguments[0] = new ParsedBindingPathNode(bindingPathText, context.GetAvaloniaTypes().CompiledBindingPath, nodes);
+                        foundPath = true;
+                    }
                 }
-                else
+                
+                if (!foundPath)
                 {
                     var bindingPathAssignment = binding.Children.OfType<XamlAstXamlPropertyValueNode>()
                         .FirstOrDefault(v => v.Property.GetClrProperty().Name == "Path");
@@ -44,12 +53,19 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
                         var reader = new CharacterReader(pathValue.Text.AsSpan());
                         var (nodes, _) = BindingExpressionGrammar.Parse(ref reader);
 
-                        if (convertedNode != null)
+                        if (nodes.Count == 1 && nodes[0] is BindingExpressionGrammar.EmptyExpressionNode)
                         {
-                            nodes.Insert(nodes.TakeWhile(x => x is BindingExpressionGrammar.ITransformNode).Count(), convertedNode);
+                            bindingPathAssignment.Values.RemoveAt(0);
                         }
+                        else
+                        {
+                            if (convertedNode != null)
+                            {
+                                nodes.Insert(nodes.TakeWhile(x => x is BindingExpressionGrammar.ITransformNode).Count(), convertedNode);
+                            }
 
-                        bindingPathAssignment.Values[0] = new ParsedBindingPathNode(pathValue, context.GetAvaloniaTypes().CompiledBindingPath, nodes);
+                            bindingPathAssignment.Values[0] = new ParsedBindingPathNode(pathValue, context.GetAvaloniaTypes().CompiledBindingPath, nodes);
+                        }
                     }
                 }
             }

tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/CompiledBindingExtensionTests.cs

@@ -938,6 +938,110 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
             }
         }
 
+        [Fact]
+        public void SupportsEmptyPath()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var xaml = @"
+<Window xmlns='https://github.com/avaloniaui'
+        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
+        xmlns:local='clr-namespace:Avalonia.Markup.Xaml.UnitTests.MarkupExtensions;assembly=Avalonia.Markup.Xaml.UnitTests'
+        x:DataType='local:TestDataContext'>
+    <TextBlock Text='{CompiledBinding}' Name='textBlock' />
+</Window>";
+                var window = (Window)AvaloniaRuntimeXamlLoader.Load(xaml);
+                var textBlock = window.FindControl<TextBlock>("textBlock");
+
+                var dataContext = new TestDataContext
+                {
+                    StringProperty = "foobar"
+                };
+
+                window.DataContext = dataContext;
+
+                Assert.Equal(typeof(TestDataContext).FullName, textBlock.Text);
+            }
+        }
+
+        [Fact]
+        public void SupportsEmptyPathWithStringFormat()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var xaml = @"
+<Window xmlns='https://github.com/avaloniaui'
+        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
+        xmlns:local='clr-namespace:Avalonia.Markup.Xaml.UnitTests.MarkupExtensions;assembly=Avalonia.Markup.Xaml.UnitTests'
+        x:DataType='local:TestDataContext'>
+    <TextBlock Text='{CompiledBinding StringFormat=bar-\{0\}}' Name='textBlock' />
+</Window>";
+                var window = (Window)AvaloniaRuntimeXamlLoader.Load(xaml);
+                var textBlock = window.FindControl<TextBlock>("textBlock");
+
+                var dataContext = new TestDataContext
+                {
+                    StringProperty = "foobar"
+                };
+
+                window.DataContext = dataContext;
+
+                Assert.Equal("bar-" + typeof(TestDataContext).FullName, textBlock.Text);
+            }
+        }
+
+        [Fact]
+        public void SupportsDotPath()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var xaml = @"
+<Window xmlns='https://github.com/avaloniaui'
+        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
+        xmlns:local='clr-namespace:Avalonia.Markup.Xaml.UnitTests.MarkupExtensions;assembly=Avalonia.Markup.Xaml.UnitTests'
+        x:DataType='local:TestDataContext'>
+    <TextBlock Text='{CompiledBinding .}' Name='textBlock' />
+</Window>";
+                var window = (Window)AvaloniaRuntimeXamlLoader.Load(xaml);
+                var textBlock = window.FindControl<TextBlock>("textBlock");
+
+                var dataContext = new TestDataContext
+                {
+                    StringProperty = "foobar"
+                };
+
+                window.DataContext = dataContext;
+
+                Assert.Equal(typeof(TestDataContext).FullName, textBlock.Text);
+            }
+        }
+
+        [Fact]
+        public void SupportsExplicitDotPathWithStringFormat()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var xaml = @"
+<Window xmlns='https://github.com/avaloniaui'
+        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
+        xmlns:local='clr-namespace:Avalonia.Markup.Xaml.UnitTests.MarkupExtensions;assembly=Avalonia.Markup.Xaml.UnitTests'
+        x:DataType='local:TestDataContext'>
+    <TextBlock Text='{CompiledBinding Path=., StringFormat=bar-\{0\}}' Name='textBlock' />
+</Window>";
+                var window = (Window)AvaloniaRuntimeXamlLoader.Load(xaml);
+                var textBlock = window.FindControl<TextBlock>("textBlock");
+
+                var dataContext = new TestDataContext
+                {
+                    StringProperty = "foobar"
+                };
+
+                window.DataContext = dataContext;
+
+                Assert.Equal("bar-" + typeof(TestDataContext).FullName, textBlock.Text);
+            }
+        }
+
         void Throws(string type, Action cb)
         {
             try