On redo, restore pre-undo cursor position

CHANGELOG.rst

@@ -234,6 +234,7 @@ Interactive improvements
 - The completion pager will no longer sometimes skip the last entry when moving through a long list (:issue:`9833`).
 - The interactive ``history delete`` interface now allows specifying index ranges like "1..5" (:issue:`9736`), and ``history delete --exact`` now properly saves the history (:issue:`10066`).
 - Command completion will now call the stock ``manpath`` on macOS, instead of a potential Homebrew version. This prevents awkward error messages (:issue:`9817`).
+- the ``redo`` special input function restores the pre-undo cursor position.
 - A new bind function ``history-pager-delete``, bound to :kbd:`Shift` + :kbd:`Delete` by default, will delete the currently-selected history pager item from history (:issue:`9454`).
 - ``fish_key_reader`` will now use printable characters as-is, so pressing "ö" no longer leads to it telling you to bind ``\u00F6`` (:issue:`9986`).
 - ``open`` can be used to launch terminal programs again, as an ``xdg-open`` bug has been fixed and a workaround has been removed  (:issue:`10045`).

src/editable_line.rs

@@ -8,6 +8,7 @@ use crate::wchar::prelude::*;
 pub struct Edit {
     /// When undoing the edit we use this to restore the previous cursor position.
     pub cursor_position_before_edit: usize,
+    pub cursor_position_before_undo: Option<usize>,
 
     /// The span of text that is replaced by this edit.
     pub range: std::ops::Range<usize>,
@@ -25,6 +26,7 @@ impl Edit {
     pub fn new(range: std::ops::Range<usize>, replacement: WString) -> Self {
         Self {
             cursor_position_before_edit: 0,
+            cursor_position_before_undo: None,
             range,
             old: WString::new(),
             replacement,
@@ -224,6 +226,8 @@ impl EditableLine {
     pub fn undo(&mut self) -> bool {
         let mut did_undo = false;
         let mut last_group_id = None;
+        let position_before_undo = self.position();
+        let end = self.undo_history.edits_applied;
         while self.undo_history.edits_applied != 0 {
             let edit = &self.undo_history.edits[self.undo_history.edits_applied - 1];
             if did_undo
@@ -247,6 +251,10 @@ impl EditableLine {
             self.set_position(old_position);
             did_undo = true;
         }
+        if did_undo {
+            let edit = &mut self.undo_history.edits[end - 1];
+            edit.cursor_position_before_undo = Some(position_before_undo);
+        }
 
         self.end_edit_group();
         self.undo_history.may_coalesce = false;
@@ -270,7 +278,7 @@ impl EditableLine {
             last_group_id = edit.group_id;
             self.undo_history.edits_applied += 1;
             apply_edit(&mut self.text, &mut self.colors, edit);
-            self.set_position(cursor_position_after_edit(edit));
+            self.set_position(edit.cursor_position_before_undo.unwrap());
             did_redo = true;
         }