fix tree view - reveal not to invalidate item command

The issue is a regression introduced in #8783
Calculation of parent chain (for id calculation) calls getChildren which dispose nodes.
This means that reveal for a node that is already revealed dispose the node and so the frontend has an id that doesn't exist in the backend anymore so tree item command is not found.

The fix is to check the cache before calling getChildren and making sure that the technical root is also in the cache.

Signed-off-by: Amiram Wingarten <amiram.wingarten@sap.com>

packages/plugin-ext/src/plugin/tree/tree-views.ts

@@ -257,8 +257,11 @@ class TreeViewExtImpl<T> implements Disposable {
         if (treeItem.id) {
             return chain.concat(treeItem.id);
         }
-        // getChildren fills this.nodes and generate ids for them which are needed later
-        const children = await this.getChildren(parentId);
+        const cachedParentNode = this.nodes.get(parentId);
+        // first try to get children length from cache since getChildren disposes old nodes, which can cause a race
+        // condition if command is executed together with reveal.
+        // If not in cache, getChildren fills this.nodes and generate ids for them which are needed later
+        const children = cachedParentNode?.children || await this.getChildren(parentId);
         if (!children) {
             return undefined; // parent is inconsistent
         }
@@ -303,13 +306,17 @@ class TreeViewExtImpl<T> implements Disposable {
 
     async getChildren(parentId: string): Promise<TreeViewItem[] | undefined> {
         const parentNode = this.nodes.get(parentId);
-        const parent = parentNode && parentNode.value;
+        const parent = parentNode?.value;
         if (parentId && !parent) {
             console.error(`No tree item with id '${parentId}' found.`);
             return [];
         }
         this.clearChildren(parentNode);
 
+        // place root in the cache
+        if (parentId === '') {
+            this.nodes.set(parentId, { id: '', dispose: () => { } });
+        }
         // ask data provider for children for cached element
         const result = await this.treeDataProvider.getChildren(parent);
         if (result) {