Fix: TreeNode#activate() now correctly expands the node as intended.

Fix: Refactored TreeRoot#clear() and removeNode() to follow the TreeNode implementation for consistent sub-node handling.

Fix: Skip collapse() in removeNode if sub-nodes are empty to support expanded states during UI refreshes/redrawing.

Author: happyhua

domino-ui/src/main/java/org/dominokit/domino/ui/tree/TreeNode.java

@@ -122,7 +122,18 @@ public abstract class TreeNode<V, N extends TreeNode<V, N, S>, S>
    * node.
    */
   private void onActivation() {
-    if (isParent()) {
+    onActivation(true);
+  }
+
+  /**
+   * Handles the logic when a tree node is "activated" (clicked or otherwise triggered), toggling
+   * expand/collapse if it's a parent node and then calling {@link #activateNode()} to highlight the
+   * node.
+   *
+   * @param toggle indicates whether the node’s state should be toggled
+   */
+  private void onActivation(boolean toggle) {
+    if (toggle && isParent()) {
       toggle();
     }
     activateNode();
@@ -345,19 +356,15 @@ public N appendChild(N... treeItems) {
   }
 
   /**
-   * Removes a specified child node from this node. If no children remain after removal, the node is
-   * collapsed.
+   * Removes a specified child node from the node's internal list of sub-nodes.
+   *
+   * <p>Note: This does not remove the element from the DOM. To detach the item visually, call
+   * {@link TreeItem#remove()} on the item itself.
    *
    * @param item the child node to remove
    */
   public void removeNode(N item) {
-    if (subNodes.contains(item)) {
-      subNodes.remove(item);
-    }
-
-    if (subNodes.isEmpty()) {
-      collapse();
-    }
+    subNodes.remove(item);
   }
 
   /**
@@ -451,18 +458,10 @@ public RootNode<V, N, S> getRootNode() {
     return parent.getRootNode();
   }
 
-  /**
-   * Retrieves this node's optional parent. If the parent is a {@code TreeNode}, returns a non-empty
-   * {@link Optional}; otherwise, it may be empty if this node is top-level.
-   *
-   * @return an {@link Optional} containing the parent node if it exists
-   */
+  /** {@inheritDoc} */
+  @Override
   public Optional<IsParentNode<V, N, S>> getParent() {
-    if (parent instanceof TreeNode) {
-      return Optional.of(parent);
-    } else {
-      return Optional.empty();
-    }
+    return Optional.ofNullable(parent);
   }
 
   /**
@@ -552,7 +551,7 @@ protected void doActivate(boolean activateParent) {
    */
   public N activate() {
     this.show(true);
-    onActivation();
+    onActivation(false);
     return (N) this;
   }
 

domino-ui/src/main/java/org/dominokit/domino/ui/tree/TreeRoot.java

@@ -238,6 +238,7 @@ public RootNode<V, N, S> getRootNode() {
    *
    * @return An empty optional.
    */
+  @Override
   public Optional<IsParentNode<V, N, S>> getParent() {
     return Optional.empty();
   }
@@ -614,15 +615,15 @@ public List<V> getActivePathValues() {
   }
 
   /**
-   * Removes the specified tree item from this tree. This method removes the tree item from the list
-   * of sub-items and calls the {@link org.dominokit.domino.ui.tree.TreeItem#remove()} method on the
-   * item to detach it from the DOM.
+   * Removes the specified item from the tree's internal list of sub-items.
+   *
+   * <p>Note: This does not remove the element from the DOM. To detach the item visually, call
+   * {@link TreeItem#remove()} on the item itself.
    *
    * @param item The tree item to be removed.
    */
   public void removeNode(N item) {
     subNodes.remove(item);
-    item.remove();
   }
 
   /**
@@ -631,7 +632,7 @@ public void removeNode(N item) {
    * @return This `Tree` instance for method chaining.
    */
   public C clear() {
-    subNodes.forEach(TreeNode::remove);
+    new ArrayList<>(subNodes).forEach(TreeNode::remove);
     return (C) this;
   }