From 8d2af508081b9dfe27b5051e7a20280d925fd7a2 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 1 Jul 2020 10:05:49 +0200
Subject: [PATCH 1/3] Add failing tests for #3552.

---
 .../Xaml/StyleTests.cs                        | 54 +++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs
index 9642f5719d..184bc3bae9 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs
@@ -382,5 +382,59 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
                 Assert.Equal(Border.WidthProperty, border.Transitions[0].Property);
             }
         }
+
+        [Fact]
+        public void Style_Can_Use_Class_Selector_With_Dash()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var xaml = @"
+<Window xmlns='https://github.com/avaloniaui'
+             xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
+    <Window.Styles>
+        <Style Selector='Border.foo-bar'>
+            <Setter Property='Background' Value='Red'/>
+        </Style>
+    </Window.Styles>
+    <StackPanel>
+        <Border Name='foo' Classes='foo-bar'/>
+    </StackPanel>
+</Window>";
+                var loader = new AvaloniaXamlLoader();
+                var window = (Window)loader.Load(xaml);
+                var foo = window.FindControl<Border>("foo");
+
+                Assert.Equal(Colors.Red, ((ISolidColorBrush)foo.Background).Color);
+            }
+        }
+
+        [Fact]
+        public void Style_Can_Use_Pseudolass_Selector_With_Dash()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var xaml = @"
+<Window xmlns='https://github.com/avaloniaui'
+             xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
+    <Window.Styles>
+        <Style Selector='Border:foo-bar'>
+            <Setter Property='Background' Value='Red'/>
+        </Style>
+    </Window.Styles>
+    <StackPanel>
+        <Border Name='foo'/>
+    </StackPanel>
+</Window>";
+                var loader = new AvaloniaXamlLoader();
+                var window = (Window)loader.Load(xaml);
+                var foo = window.FindControl<Border>("foo");
+
+                Assert.Null(foo.Background);
+
+                ((IPseudoClasses)foo.Classes).Add(":foo-bar");
+
+                Assert.Equal(Colors.Red, ((ISolidColorBrush)foo.Background).Color);
+            }
+        }
     }
 }

From 15e0507afe1015f410984a06726fc6ec3031b37d Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 1 Jul 2020 10:06:31 +0200
Subject: [PATCH 2/3] Allow dash in style class identifiers.

---
 .../Utilities/StyleClassParser.cs             | 45 +++++++++++++++++++
 .../Markup/Parsers/SelectorGrammar.cs         |  4 +-
 2 files changed, 47 insertions(+), 2 deletions(-)
 create mode 100644 src/Avalonia.Base/Utilities/StyleClassParser.cs

diff --git a/src/Avalonia.Base/Utilities/StyleClassParser.cs b/src/Avalonia.Base/Utilities/StyleClassParser.cs
new file mode 100644
index 0000000000..2db58f73d9
--- /dev/null
+++ b/src/Avalonia.Base/Utilities/StyleClassParser.cs
@@ -0,0 +1,45 @@
+using System;
+using System.Globalization;
+
+namespace Avalonia.Utilities
+{
+#if !BUILDTASK
+    public
+#endif
+    static class StyleClassParser
+    {
+        public static ReadOnlySpan<char> ParseStyleClass(this ref CharacterReader r)
+        {
+            if (IsValidIdentifierStart(r.Peek))
+            {
+                return r.TakeWhile(c => IsValidIdentifierChar(c));
+            }
+            else
+            {
+                return ReadOnlySpan<char>.Empty;
+            }
+        }
+
+        private static bool IsValidIdentifierStart(char c)
+        {
+            return char.IsLetter(c) || c == '_';
+        }
+
+        private static bool IsValidIdentifierChar(char c)
+        {
+            if (IsValidIdentifierStart(c) || c == '-')
+            {
+                return true;
+            }
+            else
+            {
+                var cat = CharUnicodeInfo.GetUnicodeCategory(c);
+                return cat == UnicodeCategory.NonSpacingMark ||
+                       cat == UnicodeCategory.SpacingCombiningMark ||
+                       cat == UnicodeCategory.ConnectorPunctuation ||
+                       cat == UnicodeCategory.Format ||
+                       cat == UnicodeCategory.DecimalDigitNumber;
+            }
+        }
+    }
+}
diff --git a/src/Markup/Avalonia.Markup/Markup/Parsers/SelectorGrammar.cs b/src/Markup/Avalonia.Markup/Markup/Parsers/SelectorGrammar.cs
index 5e0f43e066..b25e9490cd 100644
--- a/src/Markup/Avalonia.Markup/Markup/Parsers/SelectorGrammar.cs
+++ b/src/Markup/Avalonia.Markup/Markup/Parsers/SelectorGrammar.cs
@@ -154,7 +154,7 @@ namespace Avalonia.Markup.Parsers
 
         private static (State, ISyntax) ParseColon(ref CharacterReader r)
         {
-            var identifier = r.ParseIdentifier();
+            var identifier = r.ParseStyleClass();
 
             if (identifier.IsEmpty)
             {
@@ -214,7 +214,7 @@ namespace Avalonia.Markup.Parsers
 
         private static (State, ISyntax) ParseClass(ref CharacterReader r)
         {
-            var @class = r.ParseIdentifier();
+            var @class = r.ParseStyleClass();
             if (@class.IsEmpty)
             {
                 throw new ExpressionParseException(r.Position, $"Expected a class name after '.'.");

From 717905bded5e9d690600cf5f5b85e272004a9f05 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 1 Jul 2020 13:34:53 +0200
Subject: [PATCH 3/3] Added StyleClassParser to Avalonia.Build.Tasks.

---
 src/Avalonia.Build.Tasks/Avalonia.Build.Tasks.csproj | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Build.Tasks/Avalonia.Build.Tasks.csproj b/src/Avalonia.Build.Tasks/Avalonia.Build.Tasks.csproj
index 582e4499c5..5b2484382e 100644
--- a/src/Avalonia.Build.Tasks/Avalonia.Build.Tasks.csproj
+++ b/src/Avalonia.Build.Tasks/Avalonia.Build.Tasks.csproj
@@ -42,7 +42,10 @@
       <Compile Include="../Avalonia.Base/Utilities/IdentifierParser.cs">
         <Link>Markup/%(RecursiveDir)%(FileName)%(Extension)</Link>
       </Compile>
-      
+      <Compile Include="../Avalonia.Base/Utilities/StyleClassParser.cs">
+        <Link>Markup/%(RecursiveDir)%(FileName)%(Extension)</Link>
+      </Compile>
+
       <Compile Remove="../Markup/Avalonia.Markup.Xaml/XamlIl\xamlil.github\**\obj\**\*.cs" />
       <Compile Remove="../Markup/Avalonia.Markup.Xaml/XamlIl\xamlil.github\src\XamlIl\TypeSystem\SreTypeSystem.cs" />
       <PackageReference Include="Avalonia.Unofficial.Cecil" Version="20190417.2.0" PrivateAssets="All" />