Bind handleExpansionToggleDblClickEvent in TreeWidget (#9877)

Ensure `handleExpansionToggleDblClickEvent` correctly bound in TreeWidget

Co-authored-by: Scott Axcell <[email protected]>

CHANGELOG.md

@@ -10,6 +10,7 @@
 
 - [core] registering toolbar items for commands that explicitly target a `ViewContainer` rather than a child widget may not behave as expected. Such registrations should be made in the `ViewContainer` by overriding the `updateToolbarItems` method and using the `registerToolbarItem` utility. See the modifications to the `scm` and `vsx-registry` packages in the PR for examples. [#9798](https://github.com/eclipse-theia/theia/pull/9798)
 - [vsx-registry] `VSXExtensionsContribution` no longer implements `TabBarToolbarContribution` and is not bound as such. Extensions of the class that expect such behavior should reimplement it with caution. See caveats in PR. [#9798](https://github.com/eclipse-theia/theia/pull/9798)
+- [core] `handleExpansionToggleDblClickEvent` in `TreeWidget` can no longer be overridden. Instead, `doHandleExpansionToggleDblClickEvent` can be overridden. [#9877](https://github.com/eclipse-theia/theia/pull/9877)
 
 ## v1.16.0 - 7/29/2021
 

packages/core/src/browser/tree/tree-widget.tsx

@@ -1208,9 +1208,13 @@ export class TreeWidget extends ReactWidget implements StatefulWidget {
 
     /**
      * Handle the double-click mouse event on the expansion toggle.
+     */
+    protected readonly handleExpansionToggleDblClickEvent = (event: React.MouseEvent<HTMLElement>) => this.doHandleExpansionToggleDblClickEvent(event);
+    /**
+     * Actually handle the double-click mouse event on the expansion toggle.
      * @param event the double-click mouse event.
      */
-    protected handleExpansionToggleDblClickEvent(event: React.MouseEvent<HTMLElement>): void {
+    protected doHandleExpansionToggleDblClickEvent(event: React.MouseEvent<HTMLElement>): void {
         if (this.props.expandOnlyOnExpansionToggleClick) {
             // Ignore the double-click event.
             event.stopPropagation();