Fixes: U4-4182 Exception during plugins loading

src/Umbraco.Core/CoreBootManager.cs

@@ -318,11 +318,9 @@ namespace Umbraco.Core
             PropertyEditorValueConvertersResolver.Current = new PropertyEditorValueConvertersResolver(
 				PluginManager.Current.ResolvePropertyEditorValueConverters());
 
-			//add the internal ones, these are not public currently so need to add them manually
-            PropertyValueConvertersResolver.Current = new PropertyValueConvertersResolver(
-                PluginManager.Current.ResolvePropertyValueConverters());
-				// fixme - why not use the following syntax?
-                //PluginManager.Current.ResolveTypes<IPropertyValueConverter>());
+			// need to filter out the ones we dont want!!
+		    PropertyValueConvertersResolver.Current = new PropertyValueConvertersResolver(
+		        PluginManager.Current.ResolveTypes<IPropertyValueConverter>());                
 
             // use the new DefaultShortStringHelper
             ShortStringHelperResolver.Current = new ShortStringHelperResolver(

src/Umbraco.Core/HideFromTypeFinderAttribute.cs

@@ -0,0 +1,13 @@
+using System;
+
+namespace Umbraco.Core
+{
+    /// <summary>
+    /// Used to notify the TypeFinder to ignore any class attributed with this during it's discovery
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Class)]
+    public sealed class HideFromTypeFinderAttribute : Attribute
+    {
+        
+    }
+}

src/Umbraco.Core/Models/PublishedContent/PublishedPropertyType.cs

@@ -269,7 +269,7 @@ namespace Umbraco.Core.Models.PublishedContent
                 : Enumerable.Empty<IPropertyValueConverter>();
         }
 
-        class CompatConverter : PropertyValueConverterBase
+        private class CompatConverter : PropertyValueConverterBase
         {
             private readonly IPropertyEditorValueConverter _converter;
 

src/Umbraco.Core/PluginManager.cs

@@ -507,15 +507,6 @@ namespace Umbraco.Core
             return ResolveTypes<IPropertyEditorValueConverter>();
         }
 
-        /// <summary>
-        /// Returns all available PropertyValueConverter
-        /// </summary>
-        /// <returns></returns>
-        internal IEnumerable<Type> ResolvePropertyValueConverters()
-        {
-            return ResolveTypes<IPropertyValueConverter>();
-        }
-
         /// <summary>
         /// Returns all available IDataType in application
         /// </summary>

src/Umbraco.Core/TypeFinder.cs

@@ -525,8 +525,12 @@ namespace Umbraco.Core
 
                 //now filter the types based on the onlyConcreteClasses flag, not interfaces, not static classes
                 var filteredTypes = allSubTypes
-                    .Where(t => (TypeHelper.IsNonStaticClass(t)
+                    .Where(t => (TypeHelper.IsNonStaticClass(t)                                 
+                                //Do not include nested private classes - since we are in full trust now this will find those too!
+                                 && t.IsNestedPrivate == false   
                                  && (onlyConcreteClasses == false || t.IsAbstract == false)
+                                 //Do not include classes that are flagged to hide from the type finder
+                                 && t.GetCustomAttribute<HideFromTypeFinderAttribute>() == null
                                  && additionalFilter(t)))
                     .ToArray();
 

src/Umbraco.Core/TypeHelper.cs

@@ -6,7 +6,7 @@ using System.Reflection;
 
 namespace Umbraco.Core
 {
-	/// <summary>
+    /// <summary>
 	/// A utility class for type checking, this provides internal caching so that calls to these methods will be faster
 	/// than doing a manual type check in c#
 	/// </summary>

src/Umbraco.Core/Umbraco.Core.csproj

@@ -304,6 +304,7 @@
     <Compile Include="Events\RollbackEventArgs.cs" />
     <Compile Include="Events\SaveEventArgs.cs" />
     <Compile Include="Events\SendToPublishEventArgs.cs" />
+    <Compile Include="HideFromTypeFinderAttribute.cs" />
     <Compile Include="IApplicationEventHandler.cs" />
     <Compile Include="IDisposeOnRequestEnd.cs" />
     <Compile Include="IO\ResizedImage.cs" />