organize into upm directory structure

Core/ManagedReferenceUtility.cs

@@ -0,0 +1,101 @@
+#if UNITY_EDITOR
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using UnityEditor;
+using UnityEngine;
+using Object = UnityEngine.Object;
+
+public static class ManagedReferenceUtility
+{
+    /// Creates instance of passed type and assigns it to managed reference
+    public static object AssignNewInstanceOfTypeToManagedReference(this SerializedProperty serializedProperty, Type type)
+    {
+        var instance = Activator.CreateInstance(type);
+        
+        serializedProperty.serializedObject.Update(); 
+        serializedProperty.managedReferenceValue = instance;
+        serializedProperty.serializedObject.ApplyModifiedProperties(); 
+        
+        return instance;
+    }
+
+    /// Sets managed reference to null
+    public static void SetManagedReferenceToNull(this SerializedProperty serializedProperty)
+    {
+        serializedProperty.serializedObject.Update();
+        serializedProperty.managedReferenceValue = null;
+        serializedProperty.serializedObject.ApplyModifiedProperties(); 
+    }
+
+    /// Collects appropriate types based on managed reference field type and filters. Filters all derive
+    public static IEnumerable<Type> GetAppropriateTypesForAssigningToManagedReference(this SerializedProperty property, List<Func<Type, bool>> filters = null)
+    {
+        var fieldType = property.GetManagedReferenceFieldType();
+        return GetAppropriateTypesForAssigningToManagedReference(fieldType, filters);
+    }
+
+    /// Filters derived types of field typ parameter and finds ones whose are compatible with managed reference and filters.
+    public static IEnumerable<Type> GetAppropriateTypesForAssigningToManagedReference(Type fieldType, List<Func<Type, bool>> filters = null)
+    {
+        var appropriateTypes = new List<Type>();
+
+        // Get and filter all appropriate types
+        var derivedTypes = TypeCache.GetTypesDerivedFrom(fieldType);
+        foreach (var type in derivedTypes)
+        {
+            // Skips unity engine Objects (because they are not serialized by SerializeReference)
+            if (type.IsSubclassOf(typeof(Object)))
+                continue;
+            // Skip abstract classes because they should not be instantiated
+            if (type.IsAbstract)
+                continue;
+			// Skip generic classes because they can not be instantiated
+            if (type.ContainsGenericParameters)
+                continue;
+            // Skip types that has no public empty constructors (activator can not create them)    
+            if (type.IsClass && type.GetConstructor(Type.EmptyTypes) == null) // Structs still can be created (strangely)
+                continue;
+            // Filter types by provided filters if there is ones
+            if (filters != null && filters.All(f => f == null || f.Invoke(type)) == false) 
+                continue;
+
+            appropriateTypes.Add(type);
+        }
+
+        return appropriateTypes;
+    }
+    
+    /// Gets real type of managed reference
+    public static Type GetManagedReferenceFieldType(this SerializedProperty property)
+    {
+        var realPropertyType = GetRealTypeFromTypename(property.managedReferenceFieldTypename);
+        if (realPropertyType != null) 
+            return realPropertyType;
+        
+        Debug.LogError($"Can not get field type of managed reference : {property.managedReferenceFieldTypename}");
+        return null;
+    }
+    
+    /// Gets real type of managed reference's field typeName
+    public static Type GetRealTypeFromTypename(string stringType)
+    {
+        var names = GetSplitNamesFromTypename(stringType);
+        var realType = Type.GetType($"{names.ClassName}, {names.AssemblyName}");
+        return realType;
+    }
+    
+    /// Get assembly and class names from typeName
+    public static (string AssemblyName, string ClassName) GetSplitNamesFromTypename(string typename)
+    {
+        if (string.IsNullOrEmpty(typename))  
+            return ("","");
+        
+        var typeSplitString = typename.Split(char.Parse(" "));
+        var typeClassName = typeSplitString[1];
+        var typeAssemblyName = typeSplitString[0];
+        return (typeAssemblyName,  typeClassName); 
+    }
+}
+#endif

Core/ManagedReferenceUtility.cs.meta

@@ -0,0 +1,11 @@
+fileFormatVersion: 2
+guid: 07d7d3b6c96d5a04093953c060518522
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 

Core/SerializeReferenceGenericSelectionMenu.cs

@@ -0,0 +1,82 @@
+#if UNITY_EDITOR
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using UnityEditor;
+using UnityEngine;
+ 
+public static class SerializeReferenceGenericSelectionMenu
+{
+    /// Purpose.
+    /// This is generic selection menu (will appear at position).
+    /// Filtering. 
+    /// You can add substring filter here to filter by search string.
+    /// As well ass type or interface restrictions.
+    /// As well as any custom restriction that is based on input type.
+    /// And it will be performed on each Appropriate type found by TypeCache.
+    public static void ShowContextMenuForManagedReference(this SerializedProperty property, Rect position, IEnumerable<Func<Type,bool>> filters = null)
+    { 
+        var context = new GenericMenu();
+        FillContextMenu(filters, context, property);
+        context.DropDown(position);
+    }
+
+    /// Purpose.
+    /// This is generic selection menu (will appear at click position).
+    /// Filtering. 
+    /// You can add substring filter here to filter by search string.
+    /// As well ass type or interface restrictions.
+    /// As well as any custom restriction that is based on input type.
+    /// And it will be performed on each Appropriate type found by TypeCache.
+    public static void ShowContextMenuForManagedReference(this SerializedProperty property, IEnumerable<Func<Type, bool>> filters = null)
+    {
+        var context = new GenericMenu();
+        FillContextMenu(filters, context, property);
+        context.ShowAsContext();
+    }
+    
+    private static void FillContextMenu(IEnumerable<Func<Type, bool>> enumerableFilters, GenericMenu contextMenu, SerializedProperty property)
+    {
+        var filters = enumerableFilters.ToList();// Prevents possible multiple enumerations
+        
+        // Adds "Make Null" menu command
+        contextMenu.AddItem(new GUIContent("Null"), false, property.SetManagedReferenceToNull);
+         
+        // Collects appropriate types
+        var appropriateTypes = property.GetAppropriateTypesForAssigningToManagedReference(filters);
+        
+        // Adds appropriate types to menu
+        foreach (var appropriateType in appropriateTypes)
+            AddItemToContextMenu(appropriateType, contextMenu, property); 
+    }
+    
+    private static void AddItemToContextMenu(Type type, GenericMenu genericMenuContext, SerializedProperty property)
+    {
+        var assemblyName =  type.Assembly.ToString().Split('(', ',')[0];
+        var entryName = type + "  ( " + assemblyName + " )";
+        genericMenuContext.AddItem(new GUIContent(entryName), false, AssignNewInstanceCommand, new GenericMenuParameterForAssignInstanceCommand(type, property));
+    }
+    
+    private static void AssignNewInstanceCommand(object objectGenericMenuParameter )
+    {
+        var parameter = (GenericMenuParameterForAssignInstanceCommand) objectGenericMenuParameter;
+        var type = parameter.Type;
+        var property = parameter.Property;
+        property.AssignNewInstanceOfTypeToManagedReference(type);
+    }
+
+    private readonly struct GenericMenuParameterForAssignInstanceCommand
+    {
+        public GenericMenuParameterForAssignInstanceCommand(Type type, SerializedProperty property)
+        {
+            Type = type;
+            Property = property;
+        }
+        
+        public readonly SerializedProperty Property;
+        public readonly Type Type;
+    }
+} 
+
+#endif

Core/SerializeReferenceGenericSelectionMenu.cs.meta

@@ -0,0 +1,11 @@
+fileFormatVersion: 2
+guid: d7796948b498be241ba10c88bcf3d5fe
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 

Core/SerializeReferenceTypeRestrictionFilters.cs

@@ -0,0 +1,14 @@
+    using System;
+using System.Linq;
+
+public static class SerializeReferenceTypeRestrictionFilters
+{
+    public static Func<Type, bool> TypeIsNotSubclassOrEqualOrHasInterface(Type[] types) => type =>
+        TypeIsSubclassOrEqualOrHasInterface(types).Invoke(type) == false;
+
+    public static Func<Type, bool> TypeIsSubclassOrEqualOrHasInterface(Type[] types) => type =>
+        types.Any(e => e.IsInterface ? TypeHasInterface(type, e) : TypeIsSubclassOrEqual(type, e));
+
+    public static bool TypeIsSubclassOrEqual(Type type, Type comparator) =>  type.IsSubclassOf(comparator) || type == comparator;
+    public static bool TypeHasInterface(this Type type, Type comparator) =>  type.GetInterface(comparator.ToString()) != null;
+}

Core/SerializeReferenceTypeRestrictionFilters.cs.meta

@@ -0,0 +1,11 @@
+fileFormatVersion: 2
+guid: b71802ffed0a18d43901672fcbf668c9
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: