editor: Fix panic on newline below with a cursor on deleted diff hunk

crates/editor/src/editor_tests.rs

@@ -4234,6 +4234,53 @@ fn test_newline_respects_read_only(cx: &mut TestAppContext) {
     });
 }
 
+#[gpui::test]
+async fn test_newline_below_with_cursor_on_deleted_hunk(cx: &mut TestAppContext) {
+    init_test(cx, |_| {});
+    let mut cx = EditorTestContext::new(cx).await;
+
+    cx.set_state("aaa\nbbb\ncˇcc");
+    cx.set_head_text("aaa\nXXX\nbbb\nccc");
+    cx.run_until_parked();
+    cx.update_editor(|editor, window, cx| {
+        editor.expand_all_diff_hunks(&Default::default(), window, cx);
+    });
+    cx.run_until_parked();
+
+    cx.update_editor(|editor, window, cx| {
+        editor.change_selections(Default::default(), window, cx, |s| {
+            s.select_display_ranges([
+                DisplayPoint::new(DisplayRow(1), 0)..DisplayPoint::new(DisplayRow(1), 0),
+                DisplayPoint::new(DisplayRow(3), 3)..DisplayPoint::new(DisplayRow(3), 3),
+            ]);
+        });
+    });
+
+    cx.update_editor(|editor, window, cx| {
+        editor.newline_below(&NewlineBelow, window, cx);
+    });
+    cx.run_until_parked();
+
+    assert_eq!(cx.buffer(|buffer, _| buffer.text()), "aaa\nbbb\nccc\n");
+
+    let cursors = cx.update_editor(|editor, window, cx| {
+        let display_snapshot = editor.snapshot(window, cx).display_snapshot;
+        editor
+            .selections
+            .all_display(&display_snapshot)
+            .iter()
+            .map(|selection| selection.head())
+            .collect::<Vec<_>>()
+    });
+    assert_eq!(
+        cursors,
+        vec![
+            DisplayPoint::new(DisplayRow(1), 0),
+            DisplayPoint::new(DisplayRow(4), 0),
+        ],
+    );
+}
+
 #[gpui::test]
 fn test_newline_below_multibuffer(cx: &mut TestAppContext) {
     init_test(cx, |_| {});

crates/editor/src/input.rs

@@ -841,7 +841,7 @@ impl Editor {
         }
 
         let mut buffer_edits: HashMap<EntityId, (Entity<Buffer>, Vec<Point>)> = HashMap::default();
-        let mut rows = Vec::new();
+        let mut rows: Vec<Option<u32>> = Vec::new();
         let mut rows_inserted = 0;
 
         for selection in self.selections.all_adjusted(&self.display_snapshot(cx)) {
@@ -852,6 +852,7 @@ impl Editor {
             let Some((buffer_handle, buffer_point)) =
                 self.buffer.read(cx).point_to_buffer_point(point, cx)
             else {
+                rows.push(None);
                 continue;
             };
 
@@ -862,7 +863,7 @@ impl Editor {
                 .push(buffer_point);
 
             rows_inserted += 1;
-            rows.push(row + rows_inserted);
+            rows.push(Some(row + rows_inserted));
         }
 
         self.transact(window, cx, |editor, window, cx| {
@@ -882,21 +883,21 @@ impl Editor {
 
             editor.change_selections(Default::default(), window, cx, |s| {
                 let mut index = 0;
-                s.move_cursors_with(&mut |map, _, _| {
-                    let row = rows[index];
+                s.maybe_move_cursors_with(&mut |map, _, _| {
+                    let row = rows.get(index).copied().flatten();
                     index += 1;
 
-                    let point = Point::new(row, 0);
+                    let point = Point::new(row?, 0);
                     let boundary = map.next_line_boundary(point).1;
                     let clipped = map.clip_point(boundary, Bias::Left);
 
-                    (clipped, SelectionGoal::None)
+                    Some((clipped, SelectionGoal::None))
                 });
             });
 
             let mut indent_edits = Vec::new();
             let multibuffer_snapshot = editor.buffer.read(cx).snapshot(cx);
-            for row in rows {
+            for row in rows.into_iter().flatten() {
                 let indents = multibuffer_snapshot.suggested_indents(row..row + 1, cx);
                 for (row, indent) in indents {
                     if indent.len == 0 {