Fix BoxSet collapse handling and deletion

MediaBrowser.Controller/Entities/CollectionFolder.cs

@@ -79,14 +79,27 @@ namespace MediaBrowser.Controller.Entities
         public CollectionType? CollectionType { get; set; }
 
         /// <summary>
-        /// Gets the item's children.
+        /// Gets or sets the item's children.
         /// </summary>
         /// <remarks>
         /// Our children are actually just references to the ones in the physical root...
+        /// Setting to null propagates invalidation to physical folders since the getter
+        /// always delegates to <see cref="GetActualChildren"/> and never reads the backing field.
         /// </remarks>
         /// <value>The actual children.</value>
         [JsonIgnore]
-        public override IEnumerable<BaseItem> Children => GetActualChildren();
+        public override IEnumerable<BaseItem> Children
+        {
+            get => GetActualChildren();
+            set
+            {
+                // The getter delegates to physical folders, so invalidate their caches.
+                foreach (var folder in GetPhysicalFolders(true))
+                {
+                    folder.Children = null;
+                }
+            }
+        }
 
         [JsonIgnore]
         public override bool SupportsPeople => false;

MediaBrowser.Controller/Entities/Folder.cs

@@ -733,6 +733,7 @@ namespace MediaBrowser.Controller.Entities
             if (!query.ForceDirect && RequiresPostFiltering(query))
             {
                 query.CollapseBoxSetItems = true;
+                SetCollapseBoxSetItemTypes(query);
             }
 
             if (this is not UserRootFolder
@@ -1039,6 +1040,33 @@ namespace MediaBrowser.Controller.Entities
             return (queryHasMovies || queryHasSeries) && AllowBoxSetCollapsing(query);
         }
 
+        private void SetCollapseBoxSetItemTypes(InternalItemsQuery query)
+        {
+            var config = ConfigurationManager.Configuration;
+            bool collapseMovies = config.EnableGroupingMoviesIntoCollections;
+            bool collapseSeries = config.EnableGroupingShowsIntoCollections;
+
+            if (collapseMovies && collapseSeries)
+            {
+                // Empty means collapse all types
+                query.CollapseBoxSetItemTypes = [];
+                return;
+            }
+
+            var types = new List<BaseItemKind>();
+            if (collapseMovies)
+            {
+                types.Add(BaseItemKind.Movie);
+            }
+
+            if (collapseSeries)
+            {
+                types.Add(BaseItemKind.Series);
+            }
+
+            query.CollapseBoxSetItemTypes = types.ToArray();
+        }
+
         private static bool AllowBoxSetCollapsing(InternalItemsQuery request)
         {
             if (request.IsFavorite.HasValue)

MediaBrowser.Controller/Entities/InternalItemsQuery.cs

@@ -113,6 +113,12 @@ namespace MediaBrowser.Controller.Entities
 
         public bool? CollapseBoxSetItems { get; set; }
 
+        /// <summary>
+        /// Gets or sets the item types that should be collapsed into box sets.
+        /// When empty, all types are collapsed. When set, only items of these types are replaced by their parent box set.
+        /// </summary>
+        public BaseItemKind[] CollapseBoxSetItemTypes { get; set; } = [];
+
         public string? NameStartsWithOrGreater { get; set; }
 
         public string? NameStartsWith { get; set; }