fix(ClearProperty): don't inject into existing method

Existing methods most likely already handle clearing the property in
a different way compared to just setting it to null. This fix allows
to override the behavior by implementing the method manually.

BREAKING CHANGE: The ClearPropertyMethod weaver no longer injects
anything into the Clear method in case it already exists. An info
logging statement has been added that can help to find the Clear
method implementations and ensure it clears the property manually.

Sources/ClearPropertyMethod.Fody/ModuleWeaver.cs

@@ -34,10 +34,19 @@ public override void Execute()
 
             foreach (PropertyDefinition propertyDefinition in propertyDefinitions)
             {
-                MethodDefinition clearMethodDefinition =
-                    FindOrCreateClearMethod(propertyDefinition, clearMethodNamePrefix);
-                clearMethodDefinition.IsPublic = true;
-
+                string methodName = clearMethodNamePrefix
+                    + char.ToUpperInvariant(propertyDefinition.Name[0])
+                    + propertyDefinition.Name.Substring(1);
+                MethodDefinition existingMethodDefinition = FindClearMethod(propertyDefinition, methodName);
+                if (existingMethodDefinition != null)
+                {
+                    LogInfo(
+                        $"The clear method '{existingMethodDefinition.FullName}' already exists."
+                        + $" A setter call to clear the property '{propertyDefinition.FullName}' will not be inserted.");
+                    continue;
+                }
+
+                MethodDefinition clearMethodDefinition = CreateClearMethod(propertyDefinition, methodName);
                 ClearPropertyInMethod(propertyDefinition, clearMethodDefinition);
             }
         }
@@ -61,28 +70,21 @@ private IEnumerable<Regex> FindNamespaceFilters() =>
                 .ToList()
             ?? Enumerable.Empty<Regex>();
 
-        private MethodDefinition FindOrCreateClearMethod(
-            IMemberDefinition propertyDefinition,
-            string clearMethodNamePrefix)
-        {
-            string methodName = clearMethodNamePrefix
-                + char.ToUpperInvariant(propertyDefinition.Name[0])
-                + propertyDefinition.Name.Substring(1);
-            TypeReference returnTypeReference = TypeSystem.VoidReference;
-
-            MethodDefinition existingMethodDefinition = propertyDefinition.DeclaringType.Methods.FirstOrDefault(
+        private MethodDefinition FindClearMethod(IMemberDefinition propertyDefinition, string methodName) =>
+            propertyDefinition.DeclaringType.Methods.FirstOrDefault(
                 definition => string.Equals(definition.Name, methodName, StringComparison.OrdinalIgnoreCase)
-                    && definition.ReturnType.FullName == returnTypeReference.FullName
+                    && definition.ReturnType.FullName == TypeSystem.VoidReference.FullName
                     && !definition.HasParameters);
-            if (existingMethodDefinition != null)
-            {
-                return existingMethodDefinition;
-            }
 
+        private MethodDefinition CreateClearMethod(IMemberDefinition propertyDefinition, string methodName)
+        {
             MethodDefinition newMethodDefinition = new MethodDefinition(
                 methodName,
                 MethodAttributes.Public | MethodAttributes.HideBySig,
-                returnTypeReference);
+                TypeSystem.VoidReference)
+            {
+                IsPublic = true
+            };
             newMethodDefinition.CustomAttributes.Add(
                 new CustomAttribute(_compilerGeneratedAttributeConstructorReference));
             propertyDefinition.DeclaringType.Methods.Add(newMethodDefinition);