Add support for defining sections

src/RazorBlade.Analyzers.Tests/RazorBladeSourceGeneratorTests.cs

@@ -324,6 +324,19 @@ public Task should_reject_tag_helper_directives()
         );
     }
 
+    [Test]
+    public Task should_handle_sections()
+    {
+        return Verify(
+            """
+            Before section
+            @section SectionName { Section content }
+            After section
+            @section OtherSectionName { Answer is @(42) }
+            """
+        );
+    }
+
     private static GeneratorDriverRunResult Generate(string input,
                                                      string? csharpCode,
                                                      bool embeddedLibrary,

src/RazorBlade.Analyzers.Tests/RazorBladeSourceGeneratorTests.should_handle_sections#TestNamespace.TestFile.Razor.g.verified.cs

@@ -0,0 +1,37 @@
+//HintName: TestNamespace.TestFile.Razor.g.cs
+#pragma checksum "./TestFile.cshtml" "{ff1816ec-aa5e-4d10-87f7-6f4963833460}" "c5ddc67791758895b8ee73dd2a45225d3418acdb"
+// <auto-generated/>
+#pragma warning disable 1591
+namespace TestNamespace
+{
+    #line hidden
+    #nullable restore
+    internal partial class TestFile : global::RazorBlade.HtmlTemplate
+    #nullable disable
+    {
+        #pragma warning disable 1998
+        protected async override global::System.Threading.Tasks.Task ExecuteAsync()
+        {
+            WriteLiteral("Before section\r\n");
+            DefineSection("SectionName", async() => {
+                WriteLiteral(" Section content ");
+            }
+            );
+            WriteLiteral("After section\r\n");
+            DefineSection("OtherSectionName", async() => {
+                WriteLiteral(" Answer is ");
+#nullable restore
+#line (4,41)-(4,43) 6 "./TestFile.cshtml"
+Write(42);
+
+#line default
+#line hidden
+#nullable disable
+                WriteLiteral(" ");
+            }
+            );
+        }
+        #pragma warning restore 1998
+    }
+}
+#pragma warning restore 1591

src/RazorBlade.Analyzers/RazorBladeSourceGenerator.cs

@@ -5,6 +5,7 @@
 using System.Text;
 using System.Threading;
 using Microsoft.AspNetCore.Razor.Language;
+using Microsoft.AspNetCore.Razor.Language.Extensions;
 using Microsoft.AspNetCore.Razor.Language.Intermediate;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp;
@@ -112,6 +113,7 @@ private static RazorCSharpDocument GenerateRazorCode(SourceText sourceText, Inpu
             cfg =>
             {
                 ModelDirective.Register(cfg);
+                SectionDirective.Register(cfg);
 
                 cfg.SetCSharpLanguageVersion(globalOptions.ParseOptions.LanguageVersion);
 

src/RazorBlade.Library/RazorTemplate.cs

@@ -1,4 +1,6 @@
-using System.ComponentModel;
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
 using System.IO;
 using System.Threading;
 using System.Threading.Tasks;
@@ -12,6 +14,8 @@ namespace RazorBlade;
 /// </summary>
 public abstract class RazorTemplate : IEncodedContent
 {
+    private readonly Dictionary<string, Func<Task>> _sections = new(StringComparer.OrdinalIgnoreCase);
+
     /// <summary>
     /// The <see cref="TextWriter"/> which receives the output.
     /// </summary>
@@ -169,6 +173,26 @@ protected internal virtual void Write(IEncodedContent? content)
     [EditorBrowsable(EditorBrowsableState.Never)]
     protected internal abstract void EndWriteAttribute();
 
+    /// <summary>
+    /// Defines a section.
+    /// </summary>
+    /// <param name="name">The name of the section.</param>
+    /// <param name="action">The action which renders the section.</param>
+    [PublicAPI]
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    protected internal void DefineSection(string name, Func<Task> action)
+    {
+#if NETCOREAPP
+        if (!_sections.TryAdd(name, action))
+            throw new InvalidOperationException($"Section '{name}' is already defined.");
+#else
+        if (_sections.ContainsKey(name))
+            throw new InvalidOperationException($"Section '{name}' is already defined.");
+
+        _sections[name] = action;
+#endif
+    }
+
     void IEncodedContent.WriteTo(TextWriter textWriter)
         => Render(textWriter, CancellationToken.None);
 }