Add opt-in EmitShapeTag support

src/TypeGenerationModel.cs

@@ -15,13 +15,15 @@ internal TypeGenerationModel(
         string qualifiedSourceTypeName,
         string viewTypeName,
         bool isEffectivelyPublic,
+        bool emitShapeTag,
         bool isBlittableStruct,
         int blittableStructByteCount)
     {
         Symbol = symbol;
         QualifiedSourceTypeName = qualifiedSourceTypeName;
         ViewTypeName = viewTypeName;
         IsEffectivelyPublic = isEffectivelyPublic;
+        EmitShapeTag = emitShapeTag;
         IsBlittableStruct = isBlittableStruct;
         BlittableStructByteCount = blittableStructByteCount;
     }
@@ -34,6 +36,8 @@ internal TypeGenerationModel(
 
     internal bool IsEffectivelyPublic { get; }
 
+    internal bool EmitShapeTag { get; }
+
     internal bool IsBlittableStruct { get; }
 
     internal int BlittableStructByteCount { get; }

src/ZeroSerializerGenerator.cs

@@ -111,6 +111,10 @@ public void Execute(GeneratorExecutionContext executionContext)
         injectedAttributeSourceBuilder.AppendLine("    Inherited = false)]");
         injectedAttributeSourceBuilder.AppendLine($"internal sealed class {SerializerAttributeName} : Attribute");
         injectedAttributeSourceBuilder.OpenBlock();
+        injectedAttributeSourceBuilder.AppendLine("[Obsolete(\"Emitting string representation of the type will expose internal details in the resulting assembly. Consider using `ShapeHash` instead, or using `#if DEBUG` directive to prevent emitting on release build.\")]");
+        injectedAttributeSourceBuilder.AppendLine("public bool EmitShapeTag;");
+        injectedAttributeSourceBuilder.AppendLine();
+        injectedAttributeSourceBuilder.AppendLine($"public {SerializerAttributeName}() {{ }}");
         injectedAttributeSourceBuilder.CloseBlock();
         injectedAttributeSourceBuilder.CloseBlock();
         executionContext.AddSource(
@@ -285,6 +289,7 @@ private static TypeGenerationModel CreateGenerationModel(
             qualifiedSourceTypeName,
             serializableType.Name + "View",
             IsEffectivelyPublic(serializableType),
+            ShouldEmitShapeTag(serializableType),
             isBlittableStruct,
             isBlittableStruct ? blittableStructByteCount : 0);
 
@@ -365,6 +370,46 @@ private static TypeGenerationModel CreateGenerationModel(
         return generationModel;
     }
 
+    private static bool ShouldEmitShapeTag(INamedTypeSymbol serializableType)
+    {
+        foreach (SyntaxReference syntaxReference in serializableType.DeclaringSyntaxReferences)
+        {
+            if (syntaxReference.GetSyntax() is not TypeDeclarationSyntax declaration)
+            {
+                continue;
+            }
+
+            foreach (AttributeListSyntax attributeList in declaration.AttributeLists)
+            {
+                foreach (AttributeSyntax attribute in attributeList.Attributes)
+                {
+                    string attributeName = attribute.Name.ToString();
+                    if (!attributeName.EndsWith(SerializerName, StringComparison.Ordinal) &&
+                        !attributeName.EndsWith(SerializerAttributeName, StringComparison.Ordinal))
+                    {
+                        continue;
+                    }
+
+                    if (attribute.ArgumentList == null)
+                    {
+                        continue;
+                    }
+
+                    foreach (AttributeArgumentSyntax argument in attribute.ArgumentList.Arguments)
+                    {
+                        if (argument.NameEquals?.Name.Identifier.ValueText == "EmitShapeTag" &&
+                            argument.Expression.IsKind(SyntaxKind.TrueLiteralExpression))
+                        {
+                            return true;
+                        }
+                    }
+                }
+            }
+        }
+
+        return false;
+    }
+
     private static FieldGenerationModel? CreatePropertyGenerationModel(
         IPropertySymbol serializableProperty,
         HashSet<INamedTypeSymbol> allSerializableTypes)
@@ -913,9 +958,12 @@ private static void EmitView(
         sourceBuilder.AppendLine("/// <summary>");
         sourceBuilder.AppendLine($"/// Provides a deserialized view of <see cref=\"{generationModel.QualifiedSourceTypeName}\"/>.");
         sourceBuilder.AppendLine("/// </summary>");
-        sourceBuilder.AppendLine("/// <remarks>");
-        sourceBuilder.AppendLine($"/// ShapeTag: {shapeTag}");
-        sourceBuilder.AppendLine("/// </remarks>");
+        if (generationModel.EmitShapeTag)
+        {
+            sourceBuilder.AppendLine("/// <remarks>");
+            sourceBuilder.AppendLine($"/// ShapeTag: {shapeTag}");
+            sourceBuilder.AppendLine("/// </remarks>");
+        }
         sourceBuilder.AppendLine($"{viewAccessibility} readonly struct {generationModel.ViewTypeName}");
         sourceBuilder.OpenBlock();
         sourceBuilder.AppendLine("/// <summary>");
@@ -925,7 +973,11 @@ private static void EmitView(
         sourceBuilder.AppendLine($"public const int RequiredByteLength = {requiredByteLength};");
         sourceBuilder.AppendLine($"public const bool IsBlittable = {generationModel.IsBlittableStruct.ToString().ToLowerInvariant()};");
         uint shapeHash = XXHash32.HashToUInt32(shapeTag);
-        sourceBuilder.AppendLine($"public const string ShapeTag = \"{shapeTag}\";");
+        if (!generationModel.EmitShapeTag)
+        {
+            sourceBuilder.AppendLine("// To emit this, `set EmitShapeTag = true` on ZeroSerializerAttribute.");
+        }
+        sourceBuilder.AppendLine($"{(!generationModel.EmitShapeTag ? "// " : string.Empty)}public const string ShapeTag = \"{shapeTag}\";");
         sourceBuilder.AppendLine($"public const uint ShapeHash = {shapeHash}U;");
         sourceBuilder.AppendLine();
         // ReadOnlyMemory keeps the borrowed byte array reusable by ordinary and nested View structs without allocation.

tests/SerializationModels.cs

@@ -22,7 +22,7 @@
     Positive = 5,
 }
 
-[ZeroSerializer]
+[ZeroSerializer(EmitShapeTag = true)]
 public sealed class PrimitiveRecord
 {
     public bool Boolean { get; init; }
@@ -50,7 +50,7 @@
     public double Double { get; init; }
 }
 
-[ZeroSerializer]
+[ZeroSerializer(EmitShapeTag = true)]
 public sealed class EnumClass
 {
     public ByteState ByteState { get; init; }
@@ -59,7 +59,7 @@
 }
 
 [ZeroSerializer]
 public readonly struct EnumStruct
 {
     public EnumStruct(ByteState byteState, SignedState signedState)
     {
@@ -73,15 +73,15 @@
 }
 
 [StructLayout(LayoutKind.Sequential, Pack = 1)]
-[ZeroSerializer]
+[ZeroSerializer(EmitShapeTag = true)]
 public struct PackedRecord
 {
     public int Number { get; init; }
 
     public SignedState State { get; init; }
 }
 
-[ZeroSerializer]
+[ZeroSerializer(EmitShapeTag = true)]
 public sealed class PackedContainer
 {
     public PackedRecord Value { get; init; }
@@ -116,7 +116,7 @@
 }
 
 [ZeroSerializer]
 public readonly struct SmallFixedStruct
 {
     public SmallFixedStruct(int value)
     {
@@ -127,7 +127,7 @@
 }
 
 [ZeroSerializer]
 public readonly struct LargeFixedStruct
 {
     public LargeFixedStruct(long value, ByteState state)
     {
@@ -166,7 +166,7 @@
 }
 
 [ZeroSerializer]
 public struct EmptyStruct
 {
 }
 
@@ -267,7 +267,7 @@
 {
 }
 
-[ZeroSerializer]
+[ZeroSerializer(EmitShapeTag = true)]
 public sealed class SchemaSignatureTestsModel
 {
     // 1. blittable and non-blittable nested type combo
@@ -331,14 +331,14 @@
 
 [StructLayout(LayoutKind.Sequential, Pack = 1, CharSet = CharSet.Ansi)]
 [ZeroSerializer]
 public struct SequentialPackOneWithCharSetStruct
 {
     public int Value { get; init; }
 }
 
 [StructLayout(LayoutKind.Sequential, Pack = 1, Size = 7)]
 [ZeroSerializer]
 public struct SequentialPackOneWithSizeStruct
 {
     public int Value { get; init; }
 }

tests/ShapeTagEmissionTests.cs

@@ -0,0 +1,74 @@
+// Licensed under the Apache-2.0 License
+// https://github.com/sator-imaging/ZeroSerializer
+
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using System;
+using System.Linq;
+using Xunit;
+using ZeroSerializer.Generator;
+
+#pragma warning disable CS1591  // Missing XML comment for publicly visible type or member
+
+namespace ZeroSerializer.Tests;
+
+public class ShapeTagEmissionTests
+{
+    [Fact]
+    public void ShapeTagIsCommentedOutByDefault()
+    {
+        string generatedView = GenerateView("[ZeroSerializer.ZeroSerializer] public class Record { public int Value { get; set; } }");
+
+        Assert.DoesNotContain("/// <remarks>", generatedView);
+        Assert.DoesNotContain("    public const string ShapeTag", generatedView);
+        Assert.Contains("// To emit this, `set EmitShapeTag = true` on ZeroSerializerAttribute.", generatedView);
+        Assert.Contains("// public const string ShapeTag = \"v1/{int}\";", generatedView);
+        Assert.Contains("public const uint ShapeHash = ", generatedView);
+    }
+
+    [Fact]
+    public void ShapeTagAndRemarksAreEmittedWhenRequested()
+    {
+        string generatedView = GenerateView("[ZeroSerializer.ZeroSerializer(EmitShapeTag = true)] public class Record { public int Value { get; set; } }");
+
+        Assert.DoesNotContain("// public const string ShapeTag", generatedView);
+        Assert.Contains("/// <remarks>", generatedView);
+        Assert.Contains("/// ShapeTag: v1/{int}", generatedView);
+        Assert.Contains("public const string ShapeTag = \"v1/{int}\";", generatedView);
+        Assert.Contains("public const uint ShapeHash = ", generatedView);
+    }
+
+    [Fact]
+    public void InjectedAttributeExposesObsoleteEmitShapeTagField()
+    {
+        GeneratorDriverRunResult result = RunGenerator("public class Record { }");
+        string generatedAttribute = result.Results[0].GeneratedSources
+            .Single(source => source.HintName == "- ZeroSerializerAttribute.g.cs")
+            .SourceText
+            .ToString();
+
+        Assert.Contains("public bool EmitShapeTag;", generatedAttribute);
+        Assert.Contains("[Obsolete(\"Emitting string representation of the type will expose internal details", generatedAttribute);
+        Assert.Contains("public ZeroSerializerAttribute() { }", generatedAttribute);
+    }
+
+    private static string GenerateView(string source)
+    {
+        GeneratorDriverRunResult result = RunGenerator(source);
+        return result.Results[0].GeneratedSources
+            .Single(generatedSource => generatedSource.HintName == "Record.ZeroSerializer.g.cs")
+            .SourceText
+            .ToString();
+    }
+
+    private static GeneratorDriverRunResult RunGenerator(string source)
+    {
+        SyntaxTree syntaxTree = CSharpSyntaxTree.ParseText(source);
+        CSharpCompilation compilation = CSharpCompilation.Create(
+            "ShapeTagEmissionTests",
+            new[] { syntaxTree },
+            new[] { MetadataReference.CreateFromFile(typeof(Attribute).Assembly.Location) });
+        GeneratorDriver driver = CSharpGeneratorDriver.Create(new ZeroSerializerGenerator());
+        return driver.RunGenerators(compilation).GetRunResult();
+    }
+}