Fix discarding unsaved asset editor changes

- clear cached JsonAsset managed instances on discard,
- restore MaterialInstance parameter values and override flags,
- reload model assets from disk when model edits are discarded.

Source/Editor/Windows/Assets/AssetEditorWindow.cs

@@ -132,12 +132,24 @@ namespace FlaxEditor.Windows.Assets
                         // Cancel closing
                         return true;
                     }
+                    else
+                    {
+                        // Discard and close
+                        DiscardChanges();
+                    }
                 }
             }
 
             return base.OnClosing(reason);
         }
 
+        /// <summary>
+        /// Discards unsaved asset changes before closing the window.
+        /// </summary>
+        protected virtual void DiscardChanges()
+        {
+        }
+
         /// <inheritdoc />
         protected override void OnClose()
         {

Source/Editor/Windows/Assets/JsonAssetWindow.cs

@@ -243,6 +243,14 @@ namespace FlaxEditor.Windows.Assets
             base.OnAssetLoaded();
         }
 
+        /// <inheritdoc />
+        protected override void DiscardChanges()
+        {
+            Asset?.ClearInstance();
+            _object = null;
+            base.DiscardChanges();
+        }
+
         private void OpenOptionsContextMenu()
         {
             if (_optionsCM != null)

Source/Editor/Windows/Assets/MaterialInstanceWindow.cs

@@ -64,8 +64,14 @@ namespace FlaxEditor.Windows.Assets
         [CustomEditor(typeof(ParametersEditor))]
         private sealed class PropertiesProxy
         {
+            private struct ParameterState
+            {
+                public object Value;
+                public bool IsOverride;
+            }
+
             private MaterialBase _restoreBase;
-            private Dictionary<string, object> _restoreParams;
+            private Dictionary<string, ParameterState> _restoreParams;
 
             [EditorDisplay("General"), Tooltip("The base material used to override it's properties")]
             public MaterialBase BaseMaterial
@@ -181,9 +187,16 @@ namespace FlaxEditor.Windows.Assets
                 var material = Window.Asset;
                 _restoreBase = material.BaseMaterial;
                 var parameters = material.Parameters;
-                _restoreParams = new Dictionary<string, object>();
+                _restoreParams = new Dictionary<string, ParameterState>();
                 for (int i = 0; i < parameters.Length; i++)
-                    _restoreParams[parameters[i].Name] = parameters[i].Value;
+                {
+                    var p = parameters[i];
+                    _restoreParams[p.Name] = new ParameterState
+                    {
+                        Value = p.Value,
+                        IsOverride = p.IsOverride,
+                    };
+                }
             }
 
             /// <summary>
@@ -191,7 +204,7 @@ namespace FlaxEditor.Windows.Assets
             /// </summary>
             public void DiscardChanges()
             {
-                if (Window == null)
+                if (Window == null || _restoreParams == null)
                     return;
 
                 var material = Window.Asset;
@@ -200,9 +213,10 @@ namespace FlaxEditor.Windows.Assets
                 for (int i = 0; i < parameters.Length; i++)
                 {
                     var p = parameters[i];
-                    if (p.IsPublic && _restoreParams.TryGetValue(p.Name, out var value))
+                    if (p.IsPublic && _restoreParams.TryGetValue(p.Name, out var state))
                     {
-                        p.Value = value;
+                        p.Value = state.Value;
+                        p.IsOverride = state.IsOverride;
                     }
                 }
             }

Source/Editor/Windows/Assets/ModelBaseWindow.cs

@@ -834,6 +834,13 @@ namespace FlaxEditor.Windows.Assets
             base.OnAssetLoaded();
         }
 
+        /// <inheritdoc />
+        protected override void DiscardChanges()
+        {
+            _asset?.Reload();
+            base.DiscardChanges();
+        }
+
         /// <inheritdoc />
         public override void OnItemReimported(ContentItem item)
         {

Source/Engine/Content/JsonAsset.cs

@@ -93,5 +93,15 @@ namespace FlaxEngine
             string str = instance != null ? JsonSerializer.Serialize(instance) : null;
             Data = str;
         }
+
+#if FLAX_EDITOR
+        /// <summary>
+        /// Clears the cached managed instance. The next <see cref="Instance"/> access will recreate it from the asset data.
+        /// </summary>
+        public void ClearInstance()
+        {
+            _instance = null;
+        }
+#endif
     }
 }