Add support for @layout null in Blazor components

src/Compiler/Microsoft.AspNetCore.Razor.Language/test/IntegrationTests/ComponentCodeGenerationTestBase.cs

@@ -2373,6 +2373,20 @@ @layout System.Object
         CompileToAssembly(generated);
     }
 
+    [IntegrationTestFact, WorkItem("https://github.com/dotnet/razor/issues/8340")]
+    public void LayoutDirective_Null()
+    {
+        // Act
+        var generated = CompileToCSharp("""
+            @layout null
+            """);
+
+        // Assert
+        AssertDocumentNodeMatchesBaseline(generated.CodeDocument);
+        AssertCSharpDocumentMatchesBaseline(generated.CodeDocument);
+        CompileToAssembly(generated);
+    }
+
     [IntegrationTestFact]
     public void Component_AddContent_Multiline()
     {

src/Compiler/Microsoft.AspNetCore.Razor.Language/test/IntegrationTests/ComponentDirectiveIntegrationTest.cs

@@ -44,6 +44,18 @@ public void SupportsLayoutDeclarations()
         Assert.NotNull(layoutAttribute);
     }
 
+    [Fact]
+    public void SupportsLayoutNullDeclaration()
+    {
+        // Arrange/Act
+        var component = CompileToComponent(
+            "@layout null\n" +
+            "Hello");
+
+        // Assert - when layout is set to null, no layout attribute should be generated
+        Assert.Null(component.GetAttributes().FirstOrDefault(a => a.AttributeClass.Name == "LayoutAttribute"));
+    }
+
     [Fact]
     public void SupportsImplementsDeclarations()
     {

src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/LayoutDirective_Null/TestComponent.codegen.cs

@@ -0,0 +1,34 @@
+// <auto-generated/>
+#pragma warning disable 1591
+namespace Test
+{
+    #line default
+    using global::System;
+    using global::System.Collections.Generic;
+    using global::System.Linq;
+    using global::System.Threading.Tasks;
+    using global::Microsoft.AspNetCore.Components;
+    #line default
+    #line hidden
+    #nullable restore
+    public partial class TestComponent : global::Microsoft.AspNetCore.Components.ComponentBase
+    #nullable disable
+    {
+        #pragma warning disable 219
+        private void __RazorDirectiveTokenHelpers__() {
+        ((global::System.Action)(() => {
+        }
+        ))();
+        }
+        #pragma warning restore 219
+        #pragma warning disable 0414
+        private static object __o = null;
+        #pragma warning restore 0414
+        #pragma warning disable 1998
+        protected override void BuildRenderTree(global::Microsoft.AspNetCore.Components.Rendering.RenderTreeBuilder __builder)
+        {
+        }
+        #pragma warning restore 1998
+    }
+}
+#pragma warning restore 1591

src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/LayoutDirective_Null/TestComponent.ir.txt

@@ -0,0 +1,17 @@
+Document - 
+    NamespaceDeclaration -  - Test
+        UsingDirective - (3:1,1 [20] ) - global::System
+        UsingDirective - (26:2,1 [40] ) - global::System.Collections.Generic
+        UsingDirective - (69:3,1 [25] ) - global::System.Linq
+        UsingDirective - (97:4,1 [36] ) - global::System.Threading.Tasks
+        UsingDirective - (136:5,1 [45] ) - global::Microsoft.AspNetCore.Components
+        ClassDeclaration -  - public partial - TestComponent - global::Microsoft.AspNetCore.Components.ComponentBase - 
+            DesignTimeDirective - 
+                DirectiveToken - (8:0,8 [4] x:\dir\subdir\Test\TestComponent.cshtml) - null
+            CSharpCode - 
+                IntermediateToken -  - CSharp - #pragma warning disable 0414
+            CSharpCode - 
+                IntermediateToken -  - CSharp - private static object __o = null;
+            CSharpCode - 
+                IntermediateToken -  - CSharp - #pragma warning restore 0414
+            MethodDeclaration -  - protected override - void - BuildRenderTree

src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/LayoutDirective_Null/TestComponent.codegen.cs

@@ -0,0 +1,24 @@
+// <auto-generated/>
+#pragma warning disable 1591
+namespace Test
+{
+    #line default
+    using global::System;
+    using global::System.Collections.Generic;
+    using global::System.Linq;
+    using global::System.Threading.Tasks;
+    using global::Microsoft.AspNetCore.Components;
+    #line default
+    #line hidden
+    #nullable restore
+    public partial class TestComponent : global::Microsoft.AspNetCore.Components.ComponentBase
+    #nullable disable
+    {
+        #pragma warning disable 1998
+        protected override void BuildRenderTree(global::Microsoft.AspNetCore.Components.Rendering.RenderTreeBuilder __builder)
+        {
+        }
+        #pragma warning restore 1998
+    }
+}
+#pragma warning restore 1591

src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/LayoutDirective_Null/TestComponent.ir.txt

@@ -0,0 +1,9 @@
+Document - 
+    NamespaceDeclaration -  - Test
+        UsingDirective - (3:1,1 [20] ) - global::System
+        UsingDirective - (26:2,1 [40] ) - global::System.Collections.Generic
+        UsingDirective - (69:3,1 [25] ) - global::System.Linq
+        UsingDirective - (97:4,1 [36] ) - global::System.Threading.Tasks
+        UsingDirective - (136:5,1 [45] ) - global::Microsoft.AspNetCore.Components
+        ClassDeclaration -  - public partial - TestComponent - global::Microsoft.AspNetCore.Components.ComponentBase - 
+            MethodDeclaration -  - protected override - void - BuildRenderTree

src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/Components/ComponentLayoutDirectivePass.cs

@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System;
 using System.Linq;
 using System.Threading;
 using Microsoft.AspNetCore.Razor.Language.Intermediate;
@@ -33,6 +34,12 @@ protected override void ExecuteCore(
             return;
         }
 
+        // If the layout is explicitly set to null, don't generate a layout attribute
+        if (string.Equals(token.Content, "null", StringComparison.Ordinal))
+        {
+            return;
+        }
+
         var attributeNode = new CSharpCodeIntermediateNode();
         attributeNode.Children.AddRange([
             IntermediateNodeFactory.CSharpToken($"[global::{ComponentsApi.LayoutAttribute.FullTypeName}(typeof("),

src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/Extensions/DesignTimeDirectiveTargetExtension.cs

@@ -73,6 +73,12 @@ private void WriteDesignTimeDirectiveToken(CodeRenderingContext context, DesignT
                         break;
                     }
 
+                    // Skip validation for "null" which is used to disable layouts
+                    if (string.Equals(node.Content, "null", StringComparison.Ordinal))
+                    {
+                        break;
+                    }
+
                     // {node.Content} __typeHelper = default({node.Content});
                     using (context.BuildLinePragma(node.Source))
                     {