Stable sorting of notebook cell diff info (microsoft#255005)

Author: DonJayamanne

src/vs/workbench/contrib/chat/browser/chatEditing/notebook/notebookCellChanges.ts

@@ -83,6 +83,8 @@ export function countChanges(changes: ICellDiffInfo[]): number {
 }
 
 export function sortCellChanges(changes: ICellDiffInfo[]): ICellDiffInfo[] {
+	const indexes = new Map<ICellDiffInfo, number>();
+	changes.forEach((c, i) => indexes.set(c, i));
 	return [...changes].sort((a, b) => {
 		// For unchanged and modified, use modifiedCellIndex
 		if ((a.type === 'unchanged' || a.type === 'modified') &&
@@ -101,10 +103,22 @@ export function sortCellChanges(changes: ICellDiffInfo[]): ICellDiffInfo[] {
 		}
 
 		if (a.type === 'delete' && b.type === 'insert') {
-			return -1;
+			// If the deleted cell comes before the inserted cell, we want the delete to come first
+			// As this means the cell was deleted before it was inserted
+			// We would like to see the deleted cell first in the list
+			// Else in the UI it would look weird to see an inserted cell before a deleted cell,
+			// When the users operation was to first delete the cell and then insert a new one
+			// I.e. this is merely just a simple way to ensure we have a stable sort.
+			return indexes.get(a)! - indexes.get(b)!;
 		}
 		if (a.type === 'insert' && b.type === 'delete') {
-			return 1;
+			// If the deleted cell comes before the inserted cell, we want the delete to come first
+			// As this means the cell was deleted before it was inserted
+			// We would like to see the deleted cell first in the list
+			// Else in the UI it would look weird to see an inserted cell before a deleted cell,
+			// When the users operation was to first delete the cell and then insert a new one
+			// I.e. this is merely just a simple way to ensure we have a stable sort.
+			return indexes.get(a)! - indexes.get(b)!;
 		}
 
 		if ((a.type === 'delete' && b.type !== 'insert') || (a.type !== 'insert' && b.type === 'delete')) {

src/vs/workbench/contrib/chat/test/browser/chatEditingModifiedNotebookEntry.test.ts

@@ -680,7 +680,7 @@ suite('ChatEditingModifiedNotebookEntry', function () {
 			]);
 		});
 
-		test.skip('Revert first deleted with multiple cells', async function () {
+		test('Revert first deleted with multiple cells', async function () {
 			const cellsDiffInfo: ICellDiffInfo[] = [
 				{
 					diff, keep, undo, type: 'insert', originalModel: createOriginalModel('null'), originalCellIndex: undefined,