From 4012f26976957f6f099ba4b4864a0ea1f558d8c5 Mon Sep 17 00:00:00 2001
From: Maddy <12754347+MaddyDev@users.noreply.github.com>
Date: Fri, 21 Jan 2022 17:43:37 -0800
Subject: [PATCH] fix the endless loop scenario that breaks tree scroll
 (#17971)

* fix the endless loop scenario

* add comments
---
 extensions/notebook/src/book/bookTreeView.ts | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/extensions/notebook/src/book/bookTreeView.ts b/extensions/notebook/src/book/bookTreeView.ts
index 8c1c994b1b..041b551527 100644
--- a/extensions/notebook/src/book/bookTreeView.ts
+++ b/extensions/notebook/src/book/bookTreeView.ts
@@ -425,6 +425,8 @@ export class BookTreeViewProvider implements vscode.TreeDataProvider<BookTreeIte
 		}
 
 		if (shouldReveal || this._bookViewer?.visible) {
+			// CAVEAT: findAndExpandParentNode assumes that the file structure defined in the toc
+			// follows the location on disk, it can fail otherwise.
 			bookItem = notebookPath ? await this.findAndExpandParentNode(notebookPath, shouldFocus) : undefined;
 			// Select + focus item in viewlet if books viewlet is already open, or if we pass in variable
 			if (bookItem?.contextValue && bookItem.contextValue !== 'pinnedNotebook') {
@@ -461,6 +463,7 @@ export class BookTreeViewProvider implements vscode.TreeDataProvider<BookTreeIte
 		let depthOfNotebookInBook: number = path.relative(notebookPath, parentBook.bookPath).split(path.sep).length;
 		// Walk the tree, expanding parent nodes as needed to load the child nodes until
 		// we find the one for our Notebook
+		let expandedBookItems: BookTreeItem[] = [parentBook.rootNode];
 		while (depthOfNotebookInBook > -1) {
 			// check if the notebook is available in already expanded levels.
 			bookItem = parentBook.bookItems.find(b => b.tooltip === notebookPath);
@@ -478,9 +481,11 @@ export class BookTreeViewProvider implements vscode.TreeDataProvider<BookTreeIte
 				// since bookItems will not have them yet, check the sections->file property
 				bookItemToExpand = parentBook.bookItems.find(b => b.sections?.find(n => notebookFolders[notebookFolders.length - depthOfNotebookInBook - 1].indexOf(n.file.substring(n.file.lastIndexOf('/') + 1)) > -1));
 				// book isn't found even in the same level, break out and return.
-				if (!bookItemToExpand) {
+				if (!bookItemToExpand || expandedBookItems.includes(bookItemToExpand)) {
 					break;
 				}
+				// Since we don't have the same structure defined in the toc on disk,
+				// Check to see if the files are in the same level as the parent ->
 				// increment to reset the depth since parent is in the same level
 				depthOfNotebookInBook++;
 			}
@@ -492,6 +497,7 @@ export class BookTreeViewProvider implements vscode.TreeDataProvider<BookTreeIte
 			try {
 				// TO DO: Check why the reveal fails during initial load with 'TreeError [bookTreeView] Tree element not found'
 				await this._bookViewer.reveal(bookItemToExpand, { select: false, focus: shouldFocus, expand: true });
+				expandedBookItems.push(bookItemToExpand);
 			}
 			catch (e) {
 				console.error(e);