replace NetcodePatcher attribute with an attribute patched into the assembly

Author: Lordfirespeed

NetcodePatcher/Attributes/NetcodePatchedAssemblyAttribute.cs

@@ -1,17 +1,24 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.Linq;
 using Mono.Cecil;
 using Mono.Cecil.Cil;
-using NetcodePatcher.Attributes;
+using Mono.Cecil.Rocks;
 using Unity.CompilationPipeline.Common.Diagnostics;
 using Unity.CompilationPipeline.Common.ILPostProcessing;
 using Unity.Netcode.Editor.CodeGen;
+using MethodAttributes = Mono.Cecil.MethodAttributes;
+using TypeAttributes = Mono.Cecil.TypeAttributes;
 
 namespace NetcodePatcher.CodeGen;
 
 public class ApplyPatchedAttributeILPP : ILPostProcessor
 {
+    public static readonly string AttributeNamespaceSuffix = "NetcodePatcher";
+
+    public static readonly string AttributeName = "NetcodePatchedAssemblyAttribute";
+    
     public override ILPostProcessor GetInstance() => this;
 
     public override bool WillProcess(ICompiledAssembly compiledAssembly) => true;
@@ -34,9 +41,38 @@ public class ApplyPatchedAttributeILPP : ILPostProcessor
         }
 
         // do stuff
-        var attributeConstructor =
+        var patchedAttributeDefinition = new TypeDefinition(
+            $"{assemblyDefinition.Name.Name}.{AttributeNamespaceSuffix}",
+            AttributeName,
+            TypeAttributes.NestedPrivate,
+            assemblyDefinition.MainModule.ImportReference(typeof(Attribute))
+        );
+
+        var attributeUsageAttributeConstructor =
             assemblyDefinition.MainModule.ImportReference(
-                typeof(NetcodePatchedAssemblyAttribute).GetConstructor(Type.EmptyTypes));
+                typeof(AttributeUsageAttribute).GetConstructor([typeof(AttributeTargets)])
+            );
+        var attributeUsageAttribute = new CustomAttribute(attributeUsageAttributeConstructor);
+        attributeUsageAttribute.ConstructorArguments.Add(
+            new CustomAttributeArgument(assemblyDefinition.MainModule.ImportReference(typeof(AttributeTargets)), AttributeTargets.Assembly)
+        );
+        patchedAttributeDefinition.CustomAttributes.Add(attributeUsageAttribute);
+        
+        var methodAttributes = MethodAttributes.Assembly | MethodAttributes.HideBySig | MethodAttributes.SpecialName | MethodAttributes.RTSpecialName;
+        var method = new MethodDefinition(".ctor", methodAttributes, assemblyDefinition.MainModule.TypeSystem.Void);
+        method.Body.Instructions.Add(Instruction.Create(OpCodes.Ldarg_0));
+        var baseCtorReference = new MethodReference(".ctor", assemblyDefinition.MainModule.TypeSystem.Void, patchedAttributeDefinition.BaseType){HasThis = true};
+        method.Body.Instructions.Add(Instruction.Create(OpCodes.Call, baseCtorReference));
+        method.Body.Instructions.Add(Instruction.Create(OpCodes.Ret));
+        patchedAttributeDefinition.Methods.Add(method);
+        
+        assemblyDefinition.MainModule.Types.Add(patchedAttributeDefinition);
+        
+        var attributeConstructor = assemblyDefinition.MainModule
+            .ImportReference(patchedAttributeDefinition) 
+            .Resolve()
+            .GetConstructors()
+            .First();
         var attribute = new CustomAttribute(attributeConstructor);
         assemblyDefinition.CustomAttributes.Add(attribute);
 

NetcodePatcher/CodeGen/ApplyPatchedAttributeILPP.cs

@@ -2,7 +2,6 @@
 using System.IO;
 using System.Linq;
 using Mono.Cecil;
-using NetcodePatcher.Attributes;
 using Serilog;
 using Unity.CompilationPipeline.Common.Diagnostics;
 using Unity.CompilationPipeline.Common.ILPostProcessing;
@@ -12,14 +11,15 @@ namespace NetcodePatcher.CodeGen;
 
 public static class ILPostProcessorFromFile
 {
-
     public static bool HasNetcodePatchedAttribute(ICompiledAssembly assembly)
     {
         // read
         AssemblyDefinition? assemblyDefinition = CodeGenHelpers.AssemblyDefinitionFor(assembly, out _);
         if (assemblyDefinition == null) return false;
 
-        return assemblyDefinition.CustomAttributes.Any(attribute => attribute.Constructor.DeclaringType.FullName == typeof(NetcodePatchedAssemblyAttribute).FullName);
+        return assemblyDefinition.CustomAttributes.Any(
+            attribute => attribute.Constructor.DeclaringType.FullName.EndsWith($".{ApplyPatchedAttributeILPP.AttributeNamespaceSuffix}.{ApplyPatchedAttributeILPP.AttributeName}")
+        );
     }
 
     public static void ILPostProcessFile(string assemblyPath, string outputPath, string[] references, Action<string> onWarning, Action<string> onError)