Fixes #48741: Sort reverse edit operations only if order is not significant

src/vs/editor/common/model/pieceTreeTextBuffer/pieceTreeTextBuffer.ts

@@ -206,13 +206,17 @@ export class PieceTreeTextBuffer implements ITextBuffer {
 		// Sort operations ascending
 		operations.sort(PieceTreeTextBuffer._sortOpsAscending);
 
+		let hasTouchingRanges = false;
 		for (let i = 0, count = operations.length - 1; i < count; i++) {
 			let rangeEnd = operations[i].range.getEndPosition();
 			let nextRangeStart = operations[i + 1].range.getStartPosition();
 
-			if (nextRangeStart.isBefore(rangeEnd)) {
-				// overlapping ranges
-				throw new Error('Overlapping ranges are not allowed!');
+			if (nextRangeStart.isBeforeOrEqual(rangeEnd)) {
+				if (nextRangeStart.isBefore(rangeEnd)) {
+					// overlapping ranges
+					throw new Error('Overlapping ranges are not allowed!');
+				}
+				hasTouchingRanges = true;
 			}
 		}
 
@@ -256,7 +260,11 @@ export class PieceTreeTextBuffer implements ITextBuffer {
 				forceMoveMarkers: op.forceMoveMarkers
 			};
 		}
-		reverseOperations.sort((a, b) => a.sortIndex - b.sortIndex);
+
+		// Can only sort reverse operations when the order is not significant
+		if (!hasTouchingRanges) {
+			reverseOperations.sort((a, b) => a.sortIndex - b.sortIndex);
+		}
 
 		this._mightContainRTL = mightContainRTL;
 		this._mightContainNonBasicASCII = mightContainNonBasicASCII;

src/vs/editor/test/common/model/editableTextModel.test.ts

@@ -1091,4 +1091,26 @@ suite('EditorModel - EditableTextModel.applyEdits', () => {
 
 		model.dispose();
 	});
+
+	test('issue #48741: Broken undo stack with move lines up with multiple cursors', () => {
+		let model = createEditableTextModelFromString([
+			'line1',
+			'line2',
+			'line3',
+			'',
+		].join('\n'));
+
+		const undoEdits = model.applyEdits([
+			{ range: new Range(4, 1, 4, 1), text: 'line3', },
+			{ range: new Range(3, 1, 3, 6), text: null, },
+			{ range: new Range(2, 1, 3, 1), text: null, },
+			{ range: new Range(3, 6, 3, 6), text: '\nline2' }
+		]);
+
+		model.applyEdits(undoEdits);
+
+		assert.deepEqual(model.getValue(), 'line1\nline2\nline3\n');
+
+		model.dispose();
+	});
 });