bug#32200: 27.0.50; ^L characters gets auto-deleted on actions like indent-region, newline after ^L, etc.

[Noam Postavsky]

tags 32200 + patch
quit

Kaushal Modi <kaushal.modi@gmail.com> writes:

> Hello,
>
> I find this regression from emacs 26.1. It can be very easily reproduced in
> emacs -Q:
>
> 1. emacs -Q
> 2. Press C-q C-l in the scratch buffer (this will insert the  ^L character)
> 3. Now hit RET, that character will go away.
> 3-alternative: Select a region that contains that ^L char and do C-M-\
> (indent-region). That char will get deleted again.
>
> This regression is evident in all my emacs-lisp packages, because the ^L
> chars used to separate the sections disappear when I auto-indent the whole
> package.

Ah, another weird quirk of indent-line-to.  How about this:

>From ded0a965022c57b61641f87be852e0451583823d Mon Sep 17 00:00:00 2001
From: Noam Postavsky <npostavs@gmail.com>
Date: Wed, 18 Jul 2018 19:11:23 -0400
Subject: [PATCH v1] Preserve nonblank whitespace when indenting (Bug#32200)

* lisp/indent.el (indent-line-to): Remove only spaces and tabs, not
any whitespace syntax characters.
---
 lisp/indent.el | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/lisp/indent.el b/lisp/indent.el
index f7da0767dc..339d9cbe9a 100644
--- a/lisp/indent.el
+++ b/lisp/indent.el
@@ -292,7 +292,8 @@ indent-line-to
   "Indent current line to COLUMN.
 This function removes or adds spaces and tabs at beginning of line
 only if necessary.  It leaves point at end of indentation."
-  (back-to-indentation)
+  (beginning-of-line 1)
+  (skip-chars-forward " \t")
   (let ((cur-col (current-column)))
     (cond ((< cur-col column)
           (if (>= (- column (* (/ cur-col tab-width) tab-width)) tab-width)
@@ -303,8 +304,10 @@ indent-line-to
            (delete-region (progn (move-to-column column t) (point))
                           ;; The `move-to-column' call may replace
                           ;; tabs with spaces, so we can't reuse the
-                          ;; previous `back-to-indentation' point.
-                          (progn (back-to-indentation) (point)))))))
+                          ;; previous start point.
+                          (progn (beginning-of-line 1)
+                                 (skip-chars-forward " \t")
+                                 (point)))))))
 
 (defun current-left-margin ()
   "Return the left margin to use for this line.
-- 
2.11.0