Improve expand and collapse of items in TreeGrid (#9159)

Fixes a race condition when expanding multiple items.
Only one expand or collapse request should be sent from
the client before waiting for a response, otherwise the
indexing in subsequent requests will be incorrect.

Adds API to collapse and expand multiple items from the
server, reducing the amount of round trips with multiple
item expands and collapses.

HierarchyMapper now correctly keeps expanded nodes expanded
if their parent is collapsed.

1 files changed, 57 insertions, 21 deletions

diff --git a/server/src/main/java/com/vaadin/ui/TreeGrid.java b/server/src/main/java/com/vaadin/ui/TreeGrid.java
index 6d5b9bb191..4abad5e478 100644
--- a/server/src/main/java/com/vaadin/ui/TreeGrid.java
+++ b/server/src/main/java/com/vaadin/ui/TreeGrid.java
@@ -18,6 +18,7 @@ package com.vaadin.ui;
 import java.io.Serializable;
 import java.lang.reflect.Method;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collection;
 import java.util.List;
 import java.util.Objects;
@@ -227,8 +228,8 @@ public class TreeGrid<T> extends Grid<T> {
                                 .get(rowKey), true);
                     }
                 } else {
-                    if (getDataCommunicator().doExpand(rowKey, rowIndex)
-                            && userOriginated) {
+                    if (getDataCommunicator().doExpand(rowKey, rowIndex,
+                            userOriginated) && userOriginated) {
                         fireExpandEvent(getDataCommunicator().getKeyMapper()
                                 .get(rowKey), true);
                     }
@@ -441,34 +442,69 @@ public class TreeGrid<T> extends Grid<T> {
     }
 
     /**
-     * Expands the given item.
+     * Expands the given items.
      * <p>
-     * If the item is currently expanded, does nothing. If the item does not
-     * have any children, does nothing.
+     * If an item is currently expanded, does nothing. If an item does not have
+     * any children, does nothing.
      *
-     * @param item
-     *            the item to expand
+     * @param items
+     *            the items to expand
      */
-    public void expand(T item) {
-        getDataCommunicator().setPendingExpand(item).ifPresent(key -> {
-            getRpcProxy(TreeGridClientRpc.class).setExpanded(key);
-            fireExpandEvent(item, false);
-        });
+    public void expand(T... items) {
+        expand(Arrays.asList(items));
     }
 
     /**
-     * Collapses the given item.
+     * Expands the given items.
      * <p>
-     * If the item is already collapsed, does nothing.
+     * If an item is currently expanded, does nothing. If an item does not have
+     * any children, does nothing.
      *
-     * @param item
-     *            the item to collapse
+     * @param items
+     *            the items to expand
      */
-    public void collapse(T item) {
-        getDataCommunicator().collapseItem(item).ifPresent(key -> {
-            getRpcProxy(TreeGridClientRpc.class).setCollapsed(key);
-            fireCollapseEvent(item, false);
-        });
+    public void expand(Collection<T> items) {
+        List<String> expandedKeys = new ArrayList<>();
+        List<T> expandedItems = new ArrayList<>();
+        items.forEach(item -> getDataCommunicator().setPendingExpand(item)
+                .ifPresent(key -> {
+                    expandedKeys.add(key);
+                    expandedItems.add(item);
+                }));
+        getRpcProxy(TreeGridClientRpc.class).setExpanded(expandedKeys);
+        expandedItems.forEach(item -> fireExpandEvent(item, false));
+    }
+
+    /**
+     * Collapse the given items.
+     * <p>
+     * For items that are already collapsed, does nothing.
+     *
+     * @param items
+     *            the collection of items to collapse
+     */
+    public void collapse(T... items) {
+        collapse(Arrays.asList(items));
+    }
+
+    /**
+     * Collapse the given items.
+     * <p>
+     * For items that are already collapsed, does nothing.
+     *
+     * @param items
+     *            the collection of items to collapse
+     */
+    public void collapse(Collection<T> items) {
+        List<String> collapsedKeys = new ArrayList<>();
+        List<T> collapsedItems = new ArrayList<>();
+        items.forEach(item -> getDataCommunicator().collapseItem(item)
+                .ifPresent(key -> {
+                    collapsedKeys.add(key);
+                    collapsedItems.add(item);
+                }));
+        getRpcProxy(TreeGridClientRpc.class).setCollapsed(collapsedKeys);
+        collapsedItems.forEach(item -> fireCollapseEvent(item, false));
     }
 
     @Override