Fix #784 - allow complex content for HTML

The logic that binds event handlers was interfering with the code that
prevents component properties from receiving complex content.

This check was a little overzealous.

src/Microsoft.AspNetCore.Blazor.Razor.Extensions/ComplexAttributeContentPass.cs

@@ -1,6 +1,7 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System.Linq;
 using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.AspNetCore.Razor.Language.Intermediate;
 
@@ -31,7 +32,7 @@ private void ProcessAttributes(TagHelperIntermediateNode node)
             {
                 if (node.Children[i] is TagHelperPropertyIntermediateNode propertyNode)
                 {
-                    if (HasComplexChildContent(propertyNode))
+                    if (TrySimplifyContent(propertyNode) && node.TagHelpers.Any(t => t.IsComponentTagHelper()))
                     {
                         node.Diagnostics.Add(BlazorDiagnosticFactory.Create_UnsupportedComplexContent(
                             propertyNode,
@@ -42,7 +43,7 @@ private void ProcessAttributes(TagHelperIntermediateNode node)
                 }
                 else if (node.Children[i] is TagHelperHtmlAttributeIntermediateNode htmlNode)
                 {
-                    if (HasComplexChildContent(htmlNode))
+                    if (TrySimplifyContent(htmlNode) && node.TagHelpers.Any(t => t.IsComponentTagHelper()))
                     {
                         node.Diagnostics.Add(BlazorDiagnosticFactory.Create_UnsupportedComplexContent(
                             htmlNode,
@@ -54,7 +55,7 @@ private void ProcessAttributes(TagHelperIntermediateNode node)
             }
         }
 
-        private static bool HasComplexChildContent(IntermediateNode node)
+        private static bool TrySimplifyContent(IntermediateNode node)
         {
             if (node.Children.Count == 1 &&
                 node.Children[0] is HtmlAttributeIntermediateNode htmlNode &&

test/Microsoft.AspNetCore.Blazor.Build.Test/ComponentRenderingRazorIntegrationTest.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
@@ -442,5 +442,34 @@ public class SurveyPrompt : BlazorComponent
                 frame => AssertFrame.Component(frame, "Test.SurveyPrompt", 2, 0),
                 frame => AssertFrame.Attribute(frame, "Title", "<div>Test!</div>", 1));
         }
+
+
+        [Fact]
+        public void Regression_784()
+        {
+            // Arrange
+
+            // Act
+            var component = CompileToComponent(@"
+<p onmouseover=""@OnComponentHover"" style=""background: @ParentBgColor;"" />
+@functions {
+    public string ParentBgColor { get; set; } = ""#FFFFFF"";
+
+    public void OnComponentHover(UIMouseEventArgs e)
+    {
+    }
+}
+");
+
+            // Act
+            var frames = GetRenderTree(component);
+
+            // Assert
+            Assert.Collection(
+                frames,
+                frame => AssertFrame.Element(frame, "p", 3, 0),
+                frame => AssertFrame.Attribute(frame, "onmouseover", 1),
+                frame => AssertFrame.Attribute(frame, "style", "background: #FFFFFF;", 2));
+        }
     }
 }

test/Microsoft.AspNetCore.Blazor.Build.Test/DesignTimeCodeGenerationTest.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System.Linq;
@@ -441,6 +441,29 @@ public class SurveyPrompt : BlazorComponent
             CompileToAssembly(generated);
         }
 
+        [Fact]
+        public void Regression_784()
+        {
+            // Arrange
+
+            // Act
+            var generated = CompileToCSharp(@"
+<p onmouseover=""@OnComponentHover"" style=""background: @ParentBgColor;"" />
+@functions {
+    public string ParentBgColor { get; set; } = ""#FFFFFF"";
+
+    public void OnComponentHover(UIMouseEventArgs e)
+    {
+    }
+}
+");
+
+            // Assert
+            AssertDocumentNodeMatchesBaseline(generated.CodeDocument);
+            AssertCSharpDocumentMatchesBaseline(generated.CodeDocument);
+            CompileToAssembly(generated);
+        }
+
         [Fact]
         public void BindToComponent_SpecifiesValue_WithMatchingProperties()
         {

test/Microsoft.AspNetCore.Blazor.Build.Test/RuntimeCodeGenerationTest.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System.Linq;
@@ -693,6 +693,29 @@ public class SurveyPrompt : BlazorComponent
             CompileToAssembly(generated);
         }
 
+        [Fact]
+        public void Regression_784()
+        {
+            // Arrange
+
+            // Act
+            var generated = CompileToCSharp(@"
+<p onmouseover=""@OnComponentHover"" style=""background: @ParentBgColor;"" />
+@functions {
+    public string ParentBgColor { get; set; } = ""#FFFFFF"";
+
+    public void OnComponentHover(UIMouseEventArgs e)
+    {
+    }
+}
+");
+
+            // Assert
+            AssertDocumentNodeMatchesBaseline(generated.CodeDocument);
+            AssertCSharpDocumentMatchesBaseline(generated.CodeDocument);
+            CompileToAssembly(generated);
+        }
+
         [Fact]
         public void BindToComponent_SpecifiesValue_WithMatchingProperties()
         {

test/Microsoft.AspNetCore.Blazor.Build.Test/TestFiles/DesignTimeCodeGenerationTest/Regression_784/TestComponent.codegen.cs

@@ -0,0 +1,45 @@
+// <auto-generated/>
+#pragma warning disable 1591
+namespace Test
+{
+    #line hidden
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using System.Threading.Tasks;
+    using Microsoft.AspNetCore.Blazor;
+    using Microsoft.AspNetCore.Blazor.Components;
+    public class TestComponent : Microsoft.AspNetCore.Blazor.Components.BlazorComponent
+    {
+        #pragma warning disable 219
+        private void __RazorDirectiveTokenHelpers__() {
+        }
+        #pragma warning restore 219
+        #pragma warning disable 0414
+        private static System.Object __o = null;
+        #pragma warning restore 0414
+        #pragma warning disable 1998
+        protected override void BuildRenderTree(Microsoft.AspNetCore.Blazor.RenderTree.RenderTreeBuilder builder)
+        {
+            base.BuildRenderTree(builder);
+            __o = Microsoft.AspNetCore.Blazor.Components.BindMethods.GetEventHandlerValue<Microsoft.AspNetCore.Blazor.UIMouseEventArgs>(OnComponentHover);
+#line 1 "x:\dir\subdir\Test\TestComponent.cshtml"
+                                                 __o = ParentBgColor;
+
+#line default
+#line hidden
+        }
+        #pragma warning restore 1998
+#line 2 "x:\dir\subdir\Test\TestComponent.cshtml"
+
+    public string ParentBgColor { get; set; } = "#FFFFFF";
+
+    public void OnComponentHover(UIMouseEventArgs e)
+    {
+    }
+
+#line default
+#line hidden
+    }
+}
+#pragma warning restore 1591

test/Microsoft.AspNetCore.Blazor.Build.Test/TestFiles/DesignTimeCodeGenerationTest/Regression_784/TestComponent.ir.txt

@@ -0,0 +1,40 @@
+Document - 
+    NamespaceDeclaration -  - Test
+        UsingDirective - (3:1,1 [12] ) - System
+        UsingDirective - (18:2,1 [32] ) - System.Collections.Generic
+        UsingDirective - (53:3,1 [17] ) - System.Linq
+        UsingDirective - (73:4,1 [28] ) - System.Threading.Tasks
+        UsingDirective - (104:5,1 [33] ) - Microsoft.AspNetCore.Blazor
+        UsingDirective - (140:6,1 [44] ) - Microsoft.AspNetCore.Blazor.Components
+        ClassDeclaration -  - public - TestComponent - Microsoft.AspNetCore.Blazor.Components.BlazorComponent - 
+            DesignTimeDirective - 
+                DirectiveToken - (14:0,14 [32] ) - "*, Microsoft.AspNetCore.Blazor"
+                DirectiveToken - (14:0,14 [9] ) - "*, Test"
+            CSharpCode - 
+                IntermediateToken -  - CSharp - #pragma warning disable 0414
+            CSharpCode - 
+                IntermediateToken -  - CSharp - private static System.Object __o = null;
+            CSharpCode - 
+                IntermediateToken -  - CSharp - #pragma warning restore 0414
+            MethodDeclaration -  - protected override - void - BuildRenderTree
+                CSharpCode - 
+                    IntermediateToken -  - CSharp - base.BuildRenderTree(builder);
+                HtmlElement - (0:0,0 [73] x:\dir\subdir\Test\TestComponent.cshtml) - p
+                    HtmlAttribute - (16:0,16 [17] x:\dir\subdir\Test\TestComponent.cshtml) - onmouseover=" - "
+                        CSharpExpressionAttributeValue -  - 
+                            IntermediateToken -  - CSharp - Microsoft.AspNetCore.Blazor.Components.BindMethods.GetEventHandlerValue<Microsoft.AspNetCore.Blazor.UIMouseEventArgs>(
+                            IntermediateToken - (17:0,17 [16] x:\dir\subdir\Test\TestComponent.cshtml) - CSharp - OnComponentHover
+                            IntermediateToken -  - CSharp - )
+                    HtmlAttribute -  - style=" - "
+                        HtmlAttributeValue - (42:0,42 [11] x:\dir\subdir\Test\TestComponent.cshtml) - 
+                            IntermediateToken - (42:0,42 [11] x:\dir\subdir\Test\TestComponent.cshtml) - Html - background:
+                        CSharpExpressionAttributeValue - (53:0,53 [15] x:\dir\subdir\Test\TestComponent.cshtml) -  
+                            IntermediateToken - (55:0,55 [13] x:\dir\subdir\Test\TestComponent.cshtml) - CSharp - ParentBgColor
+                        HtmlAttributeValue - (68:0,68 [1] x:\dir\subdir\Test\TestComponent.cshtml) - 
+                            IntermediateToken - (68:0,68 [1] x:\dir\subdir\Test\TestComponent.cshtml) - Html - ;
+                HtmlContent - (73:0,73 [2] x:\dir\subdir\Test\TestComponent.cshtml)
+                    IntermediateToken - (73:0,73 [2] x:\dir\subdir\Test\TestComponent.cshtml) - Html - \n
+                HtmlContent - (220:7,1 [2] x:\dir\subdir\Test\TestComponent.cshtml)
+                    IntermediateToken - (220:7,1 [2] x:\dir\subdir\Test\TestComponent.cshtml) - Html - \n
+            CSharpCode - (87:1,12 [132] x:\dir\subdir\Test\TestComponent.cshtml)
+                IntermediateToken - (87:1,12 [132] x:\dir\subdir\Test\TestComponent.cshtml) - CSharp - \n    public string ParentBgColor { get; set; } = "#FFFFFF";\n\n    public void OnComponentHover(UIMouseEventArgs e)\n    {\n    }\n

test/Microsoft.AspNetCore.Blazor.Build.Test/TestFiles/DesignTimeCodeGenerationTest/Regression_784/TestComponent.mappings.txt

@@ -0,0 +1,27 @@
+Source Location: (17:0,17 [16] x:\dir\subdir\Test\TestComponent.cshtml)
+|OnComponentHover|
+Generated Location: (1005:24,136 [16] )
+|OnComponentHover|
+
+Source Location: (55:0,55 [13] x:\dir\subdir\Test\TestComponent.cshtml)
+|ParentBgColor|
+Generated Location: (1131:26,55 [13] )
+|ParentBgColor|
+
+Source Location: (87:1,12 [132] x:\dir\subdir\Test\TestComponent.cshtml)
+|
+    public string ParentBgColor { get; set; } = "#FFFFFF";
+
+    public void OnComponentHover(UIMouseEventArgs e)
+    {
+    }
+|
+Generated Location: (1290:33,12 [132] )
+|
+    public string ParentBgColor { get; set; } = "#FFFFFF";
+
+    public void OnComponentHover(UIMouseEventArgs e)
+    {
+    }
+|
+

test/Microsoft.AspNetCore.Blazor.Build.Test/TestFiles/RuntimeCodeGenerationTest/Regression_784/TestComponent.codegen.cs

@@ -0,0 +1,36 @@
+// <auto-generated/>
+#pragma warning disable 1591
+namespace Test
+{
+    #line hidden
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using System.Threading.Tasks;
+    using Microsoft.AspNetCore.Blazor;
+    using Microsoft.AspNetCore.Blazor.Components;
+    public class TestComponent : Microsoft.AspNetCore.Blazor.Components.BlazorComponent
+    {
+        #pragma warning disable 1998
+        protected override void BuildRenderTree(Microsoft.AspNetCore.Blazor.RenderTree.RenderTreeBuilder builder)
+        {
+            base.BuildRenderTree(builder);
+            builder.OpenElement(0, "p");
+            builder.AddAttribute(1, "onmouseover", Microsoft.AspNetCore.Blazor.Components.BindMethods.GetEventHandlerValue<Microsoft.AspNetCore.Blazor.UIMouseEventArgs>(OnComponentHover));
+            builder.AddAttribute(2, "style", "background:" + " " + (ParentBgColor) + ";");
+            builder.CloseElement();
+        }
+        #pragma warning restore 1998
+#line 2 "x:\dir\subdir\Test\TestComponent.cshtml"
+
+    public string ParentBgColor { get; set; } = "#FFFFFF";
+
+    public void OnComponentHover(UIMouseEventArgs e)
+    {
+    }
+
+#line default
+#line hidden
+    }
+}
+#pragma warning restore 1591

test/Microsoft.AspNetCore.Blazor.Build.Test/TestFiles/RuntimeCodeGenerationTest/Regression_784/TestComponent.ir.txt

@@ -0,0 +1,27 @@
+Document - 
+    NamespaceDeclaration -  - Test
+        UsingDirective - (3:1,1 [14] ) - System
+        UsingDirective - (18:2,1 [34] ) - System.Collections.Generic
+        UsingDirective - (53:3,1 [19] ) - System.Linq
+        UsingDirective - (73:4,1 [30] ) - System.Threading.Tasks
+        UsingDirective - (104:5,1 [35] ) - Microsoft.AspNetCore.Blazor
+        UsingDirective - (140:6,1 [46] ) - Microsoft.AspNetCore.Blazor.Components
+        ClassDeclaration -  - public - TestComponent - Microsoft.AspNetCore.Blazor.Components.BlazorComponent - 
+            MethodDeclaration -  - protected override - void - BuildRenderTree
+                CSharpCode - 
+                    IntermediateToken -  - CSharp - base.BuildRenderTree(builder);
+                HtmlElement - (0:0,0 [73] x:\dir\subdir\Test\TestComponent.cshtml) - p
+                    HtmlAttribute - (16:0,16 [17] x:\dir\subdir\Test\TestComponent.cshtml) - onmouseover=" - "
+                        CSharpExpressionAttributeValue -  - 
+                            IntermediateToken -  - CSharp - Microsoft.AspNetCore.Blazor.Components.BindMethods.GetEventHandlerValue<Microsoft.AspNetCore.Blazor.UIMouseEventArgs>(
+                            IntermediateToken - (17:0,17 [16] x:\dir\subdir\Test\TestComponent.cshtml) - CSharp - OnComponentHover
+                            IntermediateToken -  - CSharp - )
+                    HtmlAttribute -  - style=" - "
+                        HtmlAttributeValue - (42:0,42 [11] x:\dir\subdir\Test\TestComponent.cshtml) - 
+                            IntermediateToken - (42:0,42 [11] x:\dir\subdir\Test\TestComponent.cshtml) - Html - background:
+                        CSharpExpressionAttributeValue - (53:0,53 [15] x:\dir\subdir\Test\TestComponent.cshtml) -  
+                            IntermediateToken - (55:0,55 [13] x:\dir\subdir\Test\TestComponent.cshtml) - CSharp - ParentBgColor
+                        HtmlAttributeValue - (68:0,68 [1] x:\dir\subdir\Test\TestComponent.cshtml) - 
+                            IntermediateToken - (68:0,68 [1] x:\dir\subdir\Test\TestComponent.cshtml) - Html - ;
+            CSharpCode - (87:1,12 [132] x:\dir\subdir\Test\TestComponent.cshtml)
+                IntermediateToken - (87:1,12 [132] x:\dir\subdir\Test\TestComponent.cshtml) - CSharp - \n    public string ParentBgColor { get; set; } = "#FFFFFF";\n\n    public void OnComponentHover(UIMouseEventArgs e)\n    {\n    }\n

test/Microsoft.AspNetCore.Blazor.Build.Test/TestFiles/RuntimeCodeGenerationTest/Regression_784/TestComponent.mappings.txt

@@ -0,0 +1,17 @@
+Source Location: (87:1,12 [132] x:\dir\subdir\Test\TestComponent.cshtml)
+|
+    public string ParentBgColor { get; set; } = "#FFFFFF";
+
+    public void OnComponentHover(UIMouseEventArgs e)
+    {
+    }
+|
+Generated Location: (1074:24,12 [132] )
+|
+    public string ParentBgColor { get; set; } = "#FFFFFF";
+
+    public void OnComponentHover(UIMouseEventArgs e)
+    {
+    }
+|
+