Make cursor move to duplicated line when duplicating line up (#41004)

![Screen Recording 2025-10-23 at 14 50
26](https://github.com/user-attachments/assets/3427aa06-faf4-4f76-a604-bfc5af30f8ce)

Closes #40919
Follow-up of #39610

Release Notes:
- When duplicating line up, fixed cursor to move to the duplicated line

crates/editor/src/editor.rs

@@ -11551,7 +11551,7 @@ impl Editor {
                         end
                     } else {
                         text.push('\n');
-                        Point::new(rows.end.0, 0)
+                        Point::new(rows.start.0, 0)
                     }
                 } else {
                     text.push('\n');
@@ -11567,11 +11567,57 @@ impl Editor {
             }
         }
 
-        self.transact(window, cx, |this, _, cx| {
+        self.transact(window, cx, |this, window, cx| {
             this.buffer.update(cx, |buffer, cx| {
                 buffer.edit(edits, None, cx);
             });
 
+            // When duplicating upward with whole lines, move the cursor to the duplicated line
+            if upwards && whole_lines {
+                let display_map = this.display_map.update(cx, |map, cx| map.snapshot(cx));
+
+                this.change_selections(SelectionEffects::no_scroll(), window, cx, |s| {
+                    let mut new_ranges = Vec::new();
+                    let selections = s.all::<Point>(&display_map);
+                    let mut selections_iter = selections.iter().peekable();
+
+                    while let Some(first_selection) = selections_iter.next() {
+                        // Group contiguous selections together to find the total row span
+                        let mut group_selections = vec![first_selection];
+                        let mut rows = first_selection.spanned_rows(false, &display_map);
+
+                        while let Some(next_selection) = selections_iter.peek() {
+                            let next_rows = next_selection.spanned_rows(false, &display_map);
+                            if next_rows.start < rows.end {
+                                rows.end = next_rows.end;
+                                group_selections.push(selections_iter.next().unwrap());
+                            } else {
+                                break;
+                            }
+                        }
+
+                        let row_count = rows.end.0 - rows.start.0;
+
+                        // Move all selections in this group up by the total number of duplicated rows
+                        for selection in group_selections {
+                            let new_start = Point::new(
+                                selection.start.row.saturating_sub(row_count),
+                                selection.start.column,
+                            );
+
+                            let new_end = Point::new(
+                                selection.end.row.saturating_sub(row_count),
+                                selection.end.column,
+                            );
+
+                            new_ranges.push(new_start..new_end);
+                        }
+                    }
+
+                    s.select_ranges(new_ranges);
+                });
+            }
+
             this.request_autoscroll(Autoscroll::fit(), cx);
         });
     }

crates/editor/src/editor_tests.rs

@@ -5646,8 +5646,8 @@ fn test_duplicate_line(cx: &mut TestAppContext) {
         );
     });
 
-    // With `move_upwards` the selections stay in place, except for
-    // the lines inserted above them
+    // With `duplicate_line_up` the selections move to the duplicated lines,
+    // which are inserted above the original lines
     let editor = cx.add_window(|window, cx| {
         let buffer = MultiBuffer::build_simple("abc\ndef\nghi\n", cx);
         build_editor(buffer, window, cx)
@@ -5669,7 +5669,7 @@ fn test_duplicate_line(cx: &mut TestAppContext) {
                 DisplayPoint::new(DisplayRow(0), 0)..DisplayPoint::new(DisplayRow(0), 1),
                 DisplayPoint::new(DisplayRow(0), 2)..DisplayPoint::new(DisplayRow(0), 2),
                 DisplayPoint::new(DisplayRow(2), 0)..DisplayPoint::new(DisplayRow(2), 0),
-                DisplayPoint::new(DisplayRow(6), 0)..DisplayPoint::new(DisplayRow(6), 0),
+                DisplayPoint::new(DisplayRow(5), 0)..DisplayPoint::new(DisplayRow(5), 0),
             ]
         );
     });
@@ -26888,8 +26888,8 @@ fn test_duplicate_line_up_on_last_line_without_newline(cx: &mut TestAppContext)
 
             assert_eq!(
                 editor.selections.display_ranges(cx),
-                vec![DisplayPoint::new(DisplayRow(1), 0)..DisplayPoint::new(DisplayRow(1), 0)],
-                "Selection should remain on the original line"
+                vec![DisplayPoint::new(DisplayRow(0), 0)..DisplayPoint::new(DisplayRow(0), 0)],
+                "Selection should move to the duplicated line"
             );
         })
         .unwrap();