Check for duplicate add

Author: Oliver Ehrenmüller

DeepCopy.Fody/ModuleWeaver.cs

@@ -57,31 +57,35 @@ private void AddDeepCopyConstructors(IEnumerable<TypeDefinition> targets)
             foreach (var target in targets)
                 Run(target, () =>
                 {
-                    if (target.HasCopyConstructor(out var constructor))
+                    var hasAttribute = target.TryRemove(DeepCopyAttribute.AddDeepCopyConstructor, out var attribute);
+                    if (!target.HasCopyConstructor(out var constructor))
                     {
-                        if (target.Has(DeepCopyAttribute.AddDeepCopyConstructor, out var attribute)
-                            && attribute.GetArgument("Overwrite", false)
-                            || OverwriteByDefault)
-                        {
-                            AddDeepConstructor(target, ModuleDefinition.ImportReference(constructor).Resolve());
-                        }
-                        else if (!constructor.Resolve().IsPublic)
-                        {
-                            if (!OverwriteByDefault)
-                                WriteWarning($"Non-public constructor for {target.FullName} will be overwritten");
-                            AddDeepConstructor(target, ModuleDefinition.ImportReference(constructor).Resolve());
-                        }
-                        else
-                            throw new WeavingException(@"Type already has a copy constructor
-- Use [DeepCopyConstructor] on constructor to inject deep copy code
-- Use [AddDeepCopyConstructor(Overwrite=true)] on type to replace existing constructor
-- Set global config <DeepCopy OverwriteByDefault=""True"" /> in FodyWeavers.xml");
+                        AddDeepConstructor(target, null);
+                        return;
                     }
-                    else
+
+                    var constructorResolved = constructor.Resolve();
+                    if (constructorResolved.Has(DeepCopyAttribute.DeepCopyConstructor)
+                        || constructorResolved.Has(DeepCopyAttribute.InjectDeepCopy))
+                        return;
+
+                    if (hasAttribute
+                        && attribute.GetArgument("Overwrite", false)
+                        || OverwriteByDefault)
                     {
-                        AddDeepConstructor(target, null);
+                        AddDeepConstructor(target, ModuleDefinition.ImportReference(constructor).Resolve());
+                    }
+                    else if (!constructorResolved.IsPublic)
+                    {
+                        if (!OverwriteByDefault)
+                            WriteWarning($"Non-public constructor for {target.FullName} will be overwritten");
+                        AddDeepConstructor(target, ModuleDefinition.ImportReference(constructor).Resolve());
                     }
-                    target.TryRemove(DeepCopyAttribute.AddDeepCopyConstructor);
+                    else
+                        throw new WeavingException(@"Type already has a copy constructor
+- Use [DeepCopyConstructor] on constructor to inject deep copy code
+- Use [AddDeepCopyConstructor(Overwrite=true)] on type to replace existing constructor
+- Set global config <DeepCopy OverwriteByDefault=""True"" /> in FodyWeavers.xml");
                 });
         }
 

DeepCopy.Fody/Utils/AttributeExtensions.cs

@@ -33,7 +33,12 @@ public static bool Has(this ICustomAttributeProvider attributeProvider, DeepCopy
 
         public static bool TryRemove(this ICustomAttributeProvider attributeProvider, DeepCopyAttribute name)
         {
-            if (!attributeProvider.Has(name, out var attribute))
+            return TryRemove(attributeProvider, name, out _);
+        }
+        
+        public static bool TryRemove(this ICustomAttributeProvider attributeProvider, DeepCopyAttribute name, out CustomAttribute attribute)
+        {
+            if (!attributeProvider.Has(name, out attribute))
                 return false;
             attributeProvider.CustomAttributes.Remove(attribute);
             return true;