Fold C# statement blocks

Author: davidwengier

src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/Folding/RazorCSharpStatementFoldingProvider.cs

@@ -0,0 +1,32 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the MIT license. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Razor.Language;
+using Microsoft.AspNetCore.Razor.Language.Syntax;
+using Microsoft.CodeAnalysis.Razor.ProjectSystem;
+using Microsoft.CodeAnalysis.Razor.Workspaces;
+using Microsoft.VisualStudio.LanguageServer.Protocol;
+
+namespace Microsoft.AspNetCore.Razor.LanguageServer.Folding;
+
+internal sealed class RazorCSharpStatementFoldingProvider : AbstractSyntaxNodeFoldingProvider<CSharpStatementSyntax>
+{
+    protected override string GetCollapsedText(CSharpStatementSyntax node)
+    {
+        return "@{...}";
+    }
+
+    protected override ImmutableArray<CSharpStatementSyntax> GetFoldableNodes(RazorSyntaxTree syntaxTree)
+    {
+        return syntaxTree.Root
+            .DescendantNodes(node => node is RazorDocumentSyntax or MarkupBlockSyntax or MarkupElementSyntax or CSharpCodeBlockSyntax)
+            .OfType<CSharpStatementSyntax>()
+            .SelectAsArray(d => d);
+    }
+}

src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/RazorLanguageServer.cs

@@ -131,6 +131,7 @@ protected override ILspServices ConstructLspServices()
 
         // Folding Range Providers
         services.AddSingleton<IRazorFoldingRangeProvider, RazorCodeBlockFoldingProvider>();
+        services.AddSingleton<IRazorFoldingRangeProvider, RazorCSharpStatementFoldingProvider>();
         services.AddSingleton<IRazorFoldingRangeProvider, SectionDirectiveFoldingProvider>();
         services.AddSingleton<IRazorFoldingRangeProvider, UsingsFoldingRangeProvider>();
 

src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Folding/FoldingEndpointTest.cs

@@ -33,6 +33,50 @@ @using System.CodeDom|]
             <p>hello!</p>
             """);
 
+    [Fact]
+    public Task CSharpStatement()
+       => VerifyRazorFoldsAsync("""
+            <p>hello!</p>
+
+            [|@{
+                var helloWorld = "";
+            }|]
+
+            @(DateTime
+                .Now)
+
+            <p>hello!</p>
+            """);
+
+    [Fact]
+    public Task CSharpStatement_Nested()
+      => VerifyRazorFoldsAsync("""
+            <p>hello!</p>
+
+            <div>
+
+                [|@{
+                    var helloWorld = "";
+                }|]
+
+            </div>
+
+            @(DateTime
+                .Now)
+
+            <p>hello!</p>
+            """);
+
+    [Fact]
+    public Task CSharpStatement_NotSingleLine()
+    => VerifyRazorFoldsAsync("""
+            <p>hello!</p>
+
+            @{ var helloWorld = ""; }
+
+            <p>hello!</p>
+            """);
+
     [Fact]
     public Task CodeBlock()
        => VerifyRazorFoldsAsync("""
@@ -100,6 +144,7 @@ private async Task VerifyRazorFoldsAsync(string input, string? filePath = null)
             [
                 new UsingsFoldingRangeProvider(),
                 new RazorCodeBlockFoldingProvider(),
+                new RazorCSharpStatementFoldingProvider(),
                 new SectionDirectiveFoldingProvider()
             ],
             LoggerFactory);