[PATCH 2/2] Prevent deletion of newline added by narrowing

[Leo Vivier <leo.vivier@gmail.com>]

* lisp/org.el (org-delete-backward-char): Prevent deletion of newline
  added by narrowing
  (org-delete-char): Prevent deletion of newline added by narrowing
  (org-kill-line): Prevent deletion of newline added by narrowing
  (org-kill-region): Create wrapper for `kill-region' to prevent
  deletion of newline added by narrowing

* lisp/org-keys.el (org-remap): Remap `kill-region' to
  `org-kill-region'

This ensures that the newline added by the narrowing commands cannot
be deleted by the user.

It does so by having every interactive deletion command check whether
it would delete the last newline of a narrowed buffer.  If it would,
the new command deletes whatever the original command normally would
but keep the last newline.  If the original command would have
resulted in a movement, e.g. `org-delete-backward-char', the new
command also moves the point as if the last newline had been deleted.
---
 lisp/org-keys.el |  1 +
 lisp/org.el      | 28 ++++++++++++++++++++++++----
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/lisp/org-keys.el b/lisp/org-keys.el
index 90e8139b0..26a3852b3 100644
--- a/lisp/org-keys.el
+++ b/lisp/org-keys.el
@@ -532,6 +532,7 @@ COMMANDS is a list of alternating OLDDEF NEWDEF command names."
 	   'delete-char            'org-delete-char
 	   'delete-backward-char   'org-delete-backward-char
 	   'kill-line              'org-kill-line
+	   'kill-region            'org-kill-region
 	   'widen                  'org-widen
 	   'open-line              'org-open-line
 	   'yank                   'org-yank
diff --git a/lisp/org.el b/lisp/org.el
index 3110f14ba..02130ab6a 100644
--- a/lisp/org.el
+++ b/lisp/org.el
@@ -18851,7 +18851,11 @@ because, in this case the deletion might narrow the column."
 	     (looking-at-p ".*?|")
 	     (org-at-table-p))
 	(progn (forward-char -1) (org-delete-char 1))
-      (backward-delete-char N)
+      (if (and (eobp)
+               (save-excursion (forward-char -1)
+                               (looking-at "\n")))
+          (forward-char -1)
+        (backward-delete-char N))
       (org-fix-tags-on-the-fly))))
 
 (defun org-delete-char (N)
@@ -18868,7 +18872,9 @@ because, in this case the deletion might narrow the column."
 	  (eq (char-after) ?|)
 	  (save-excursion (skip-chars-backward " \t") (bolp))
 	  (not (org-at-table-p)))
-      (delete-char N)
+      (unless (and (save-excursion (forward-char) (eobp))
+                    (looking-at "\n"))
+         (delete-char N))
       (org-fix-tags-on-the-fly))
      ((looking-at ".\\(.*?\\)|")
       (let* ((update? org-table-may-need-update)
@@ -22301,8 +22307,12 @@ depending on context."
       (user-error
        (substitute-command-keys
 	"`\\[org-kill-line]' aborted as it would kill a hidden subtree")))
-    (call-interactively
-     (if (bound-and-true-p visual-line-mode) 'kill-visual-line 'kill-line)))
+    (unless (and (looking-at-p "\n")
+		 (save-excursion
+		   (forward-char 1)
+		   (eobp)))
+      (call-interactively
+       (if (bound-and-true-p visual-line-mode) 'kill-visual-line 'kill-line))))
    ((org-match-line org-tag-line-re)
     (let ((end (save-excursion
 		 (goto-char (match-beginning 1))
@@ -22314,6 +22324,16 @@ depending on context."
     (org-align-tags))
    (t (kill-region (point) (line-end-position)))))
 
+(defun org-kill-region (beg end &optional region)
+  (interactive (list (mark) (point) 'region))
+  (kill-region
+   beg
+   end
+   region)
+  (save-excursion
+    (when (eobp)
+	(insert "\n"))))
+
 (defun org-yank (&optional arg)
   "Yank.  If the kill is a subtree, treat it specially.
 This command will look at the current kill and check if is a single
-- 
2.20.1