Fix style without selector not finding target type (#18026)

* Add failing style test without selector

* Fix XAML target type of style without selector

* Address review

* Throw for style without selector in ControlTheme
#Conflicts:
#	tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs

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

@@ -32,8 +32,26 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
             var pn = on.Children.OfType<XamlAstXamlPropertyValueNode>()
                 .FirstOrDefault(p => p.Property.GetClrProperty().Name == "Selector");
 
+            // Missing selector, use the object's target type if available
             if (pn == null)
+            {
+                // We already went through this node
+                if (context.ParentNodes().FirstOrDefault() is AvaloniaXamlIlTargetTypeMetadataNode metadataNode
+                    && metadataNode.Value == on)
+                {
+                    return node;
+                }
+
+                if (FindStyleParentObject(on, context) is { } parentObjectNode)
+                {
+                    return new AvaloniaXamlIlTargetTypeMetadataNode(
+                        on,
+                        new XamlAstClrTypeReference(node, parentObjectNode.Type.GetClrType(), false),
+                        AvaloniaXamlIlTargetTypeMetadataNode.ScopeTypes.Style);
+                }
+
                 return node;
+            }
 
             if (pn.Values.Count != 1)
                 throw new XamlSelectorsTransformException("Selector property should have exactly one value",
@@ -195,6 +213,20 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
             pn.Values[0] = selector;
 
             var templateType = GetLastTemplateTypeFromSelector(selector);
+
+            // Empty selector, use the object's target type if available
+            if (selector == initialNode)
+            {
+                if (FindStyleParentObject(on, context) is { } parentObjectNode)
+                {
+                    return new AvaloniaXamlIlTargetTypeMetadataNode(
+                        on,
+                        new XamlAstClrTypeReference(node, parentObjectNode.Type.GetClrType(), false),
+                        AvaloniaXamlIlTargetTypeMetadataNode.ScopeTypes.Style);
+                }
+
+                return node;
+            }
             
             var styleNode = new AvaloniaXamlIlTargetTypeMetadataNode(on,
                 new XamlAstClrTypeReference(selector, selector.TargetType!, false),
@@ -209,6 +241,29 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
             };
         }
 
+        private static XamlAstObjectNode? FindStyleParentObject(XamlAstNode styleNode, AstTransformationContext context)
+        {
+            var avaloniaTypes = context.GetAvaloniaTypes();
+
+            var parentNode = context
+                .ParentNodes()
+                .OfType<XamlAstObjectNode>()
+                .FirstOrDefault(n => !avaloniaTypes.Styles.IsAssignableFrom(n.Type.GetClrType()));
+
+            if (parentNode is not null)
+            {
+                var parentType = parentNode.Type.GetClrType();
+
+                if (avaloniaTypes.StyledElement.IsAssignableFrom(parentType))
+                    return parentNode;
+
+                if (avaloniaTypes.ControlTheme.IsAssignableFrom(parentType))
+                    throw new XamlTransformException("Cannot add a Style without selector to a ControlTheme.", styleNode);
+            }
+
+            return null;
+        }
+
         private static IXamlType? GetLastTemplateTypeFromSelector(XamlIlSelectorNode? node)
         {
             while (node is not null)

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

@@ -126,6 +126,7 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
         public IXamlType UriKind { get; }
         public IXamlConstructor UriConstructor { get; }
         public IXamlType Style { get; }
+        public IXamlType Styles { get; }
         public IXamlType ControlTheme { get; }
         public IXamlType WindowTransparencyLevel { get; }
         public IXamlType IReadOnlyListOfT { get; }
@@ -324,6 +325,7 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
             UriKind = cfg.TypeSystem.GetType("System.UriKind");
             UriConstructor = Uri.GetConstructor(new List<IXamlType>() { cfg.WellKnownTypes.String, UriKind });
             Style = cfg.TypeSystem.GetType("Avalonia.Styling.Style");
+            Styles = cfg.TypeSystem.GetType("Avalonia.Styling.Styles");
             ControlTheme = cfg.TypeSystem.GetType("Avalonia.Styling.ControlTheme");
             ControlTemplate = cfg.TypeSystem.GetType("Avalonia.Markup.Xaml.Templates.ControlTemplate");
             IReadOnlyListOfT = cfg.TypeSystem.GetType("System.Collections.Generic.IReadOnlyList`1");

tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs

@@ -15,6 +15,7 @@ using Xunit;
 
 namespace Avalonia.Markup.Xaml.UnitTests.Xaml
 {
+    [InvariantCulture]
     public class StyleTests : XamlTestBase
     {
         [Fact]