bug#19102: 24.4; outline-move-subtree-up/down error at last and second-last subtree

[Stephen Berman]

On Wed, 19 Nov 2014 18:29:01 +1000 Paul Rankin <paul@tilk.co> wrote:

> 1. emacs -Q
> 2. M-x switch-to-buffer RET test
> 3. M-x outline-mode
> 4. insert:
>    * one
>    * two
>    * three
> 5. position point at "* three"
> 6. M-x outline-move-subtree-up
>    => Wrong type argument: number-or-marker-p, nil
> 7. position point at "* two"
> 8. M-x outline-move-subtree-down
>    => Wrong type argument: number-or-marker-p, nil
>
> Expected behaviour:
>
> - at 6. subtree "* three" should move above "* two"
> - or at 8. subtree "* two" should move below "* three"

The following patch (against master) seems to fix this, though it could
probably be done more elegantly.

Steve Berman

diff --git a/lisp/outline.el b/lisp/outline.el
index c7cad31..bfed982 100644
--- a/lisp/outline.el
+++ b/lisp/outline.el
@@ -649,17 +649,27 @@ the match data is set appropriately."
                   'outline-get-last-sibling))
        (ins-point (make-marker))
        (cnt (abs arg))
+       ;; Make sure we can move forward when needed (bug#19102).
+       (maybe-forward-char (lambda ()
+                             (when (and (eobp) (not (bolp)))
+                               (newline))
+                             (unless (bolp)
+                               (if (= (char-after) ?\n)
+                                   (forward-char 1)))))
+       (empty-last-line (save-excursion
+                          (goto-char (point-max))
+                          (and (bolp) (eolp))))
        beg end folded)
-    ;; Select the tree
+    ;; Select the tree.
     (outline-back-to-heading)
     (setq beg (point))
     (save-match-data
       (save-excursion (outline-end-of-heading)
                      (setq folded (outline-invisible-p)))
       (outline-end-of-subtree))
-    (if (= (char-after) ?\n) (forward-char 1))
+    (funcall maybe-forward-char)
     (setq end (point))
-    ;; Find insertion point, with error handling
+    ;; Find insertion point, with error handling.
     (goto-char beg)
     (while (> cnt 0)
       (or (funcall movfunc)
@@ -667,14 +677,19 @@ the match data is set appropriately."
                 (error "Cannot move past superior level")))
       (setq cnt (1- cnt)))
     (if (> arg 0)
-       ;; Moving forward - still need to move over subtree
+       ;; Moving forward - still need to move over subtree.
        (progn (outline-end-of-subtree)
-              (if (= (char-after) ?\n) (forward-char 1))))
+              (funcall maybe-forward-char)))
     (move-marker ins-point (point))
     (insert (delete-and-extract-region beg end))
     (goto-char ins-point)
     (if folded (hide-subtree))
-    (move-marker ins-point nil)))
+    (move-marker ins-point nil)
+    ;; Clean up if necessary.
+    (save-excursion
+      (goto-char (point-max))
+      (when (and (bolp) (eolp) (not empty-last-line))
+       (delete-char -1)))))
 
 (defun outline-end-of-heading ()
   (if (re-search-forward outline-heading-end-regexp nil 'move)