From d37615bea848e83ff19c9d4fd3904f8c677f48bf Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@users.noreply.github.com>
Date: Sat, 2 Mar 2019 16:34:29 +0100
Subject: [PATCH] Added failing test for #1898.

Plus a couple of other empty binding path tests.
---
 .../Data/BindingTests.cs                      | 33 +++++++++++++++++++
 .../Parsers/ExpressionNodeBuilderTests.cs     |  9 +++++
 .../ExpressionNodeBuilderTests_Errors.cs      |  7 ++++
 3 files changed, 49 insertions(+)

diff --git a/tests/Avalonia.Markup.UnitTests/Data/BindingTests.cs b/tests/Avalonia.Markup.UnitTests/Data/BindingTests.cs
index 82b57224f0..baa1bca76a 100644
--- a/tests/Avalonia.Markup.UnitTests/Data/BindingTests.cs
+++ b/tests/Avalonia.Markup.UnitTests/Data/BindingTests.cs
@@ -273,6 +273,39 @@ namespace Avalonia.Markup.UnitTests.Data
             Assert.Equal(42, target.Value);
         }
 
+        [Fact]
+        public void Null_Path_Should_Bind_To_DataContext()
+        {
+            var target = new TextBlock { DataContext = "foo" };
+            var binding = new Binding();
+
+            target.Bind(TextBlock.TextProperty, binding);
+
+            Assert.Equal("foo", target.Text);
+        }
+
+        [Fact]
+        public void Empty_Path_Should_Bind_To_DataContext()
+        {
+            var target = new TextBlock { DataContext = "foo" };
+            var binding = new Binding { Path = string.Empty };
+
+            target.Bind(TextBlock.TextProperty, binding);
+
+            Assert.Equal("foo", target.Text);
+        }
+
+        [Fact]
+        public void Dot_Path_Should_Bind_To_DataContext()
+        {
+            var target = new TextBlock { DataContext = "foo" };
+            var binding = new Binding { Path = "." };
+
+            target.Bind(TextBlock.TextProperty, binding);
+
+            Assert.Equal("foo", target.Text);
+        }
+
         /// <summary>
         /// Tests a problem discovered with ListBox with selection.
         /// </summary>
diff --git a/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionNodeBuilderTests.cs b/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionNodeBuilderTests.cs
index 2d687ff4f7..7061915a52 100644
--- a/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionNodeBuilderTests.cs
+++ b/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionNodeBuilderTests.cs
@@ -36,6 +36,15 @@ namespace Avalonia.Markup.UnitTests.Parsers
             AssertIsProperty(result[0], "F0o");
         }
 
+        [Fact]
+        public void Should_Build_Dot()
+        {
+            var result = ToList(ExpressionObserverBuilder.Parse("."));
+
+            Assert.Equal(1, result.Count);
+            Assert.IsType<EmptyExpressionNode>(result[0]);
+        }
+
         [Fact]
         public void Should_Build_Property_Chain()
         {
diff --git a/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionNodeBuilderTests_Errors.cs b/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionNodeBuilderTests_Errors.cs
index 347fc0a744..ac385b4cab 100644
--- a/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionNodeBuilderTests_Errors.cs
+++ b/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionNodeBuilderTests_Errors.cs
@@ -30,6 +30,13 @@ namespace Avalonia.Markup.UnitTests.Parsers
                 () => ExpressionObserverBuilder.Parse("Foo.Bar."));
         }
 
+        [Fact]
+        public void Expression_Cannot_Start_With_Period_Then_Token()
+        {
+            Assert.Throws<ExpressionParseException>(
+                () => ExpressionObserverBuilder.Parse(".Bar"));
+        }
+
         [Fact]
         public void Expression_Cannot_Have_Empty_Indexer()
         {