Subject: Re: bug#21785: 25.0.50; sort-fields fails if region ends in a newline and sort-paragraph fails if it doesn't

From: Lars Ingebrigtsen <[email-masked]>
Date: Thu, 01 Aug 2019 20:38:31 +0200

(I'm going through old bug reports that have unfortunately not gotten
any responses.)

Artur Malabarba <[email-masked]> writes:

> I noticed this while writing tests for sort.el
>
> With the following buffer contents (the text between the dashes,
> including a final newline), issue `C-x h M-x sort-numeric-fields'.
> You'll get the error that the last line doesn't have enough fields. I
> think that error should not be thrown because of a final newline.
>
> ---------------------
> 1 hi
> 2 bye
>
> ----------------------
>
> Meanwhile take the following buffer contents,
> --------------------
> paragraph 2
>
> paragraph 1
> --------------------
>
> If you issue `sort-paragraphs' on the whole buffer, you'll get this:
> --------------------
> paragraph 1
> paragraph 2
>
> -------------------
>
> In my opinion both behavior are bugs. But surely one of them is, as
> the functions should be somewhat consistent on demanding final
> newlines.

I don't really think this first is a bug. You've asked Emacs to sort
numeric fields, and one of the lines in question doesn't have a numeric
field, so bugging out seems like what's required.

The second does seem like a bug.  If the final paragraph doesn't end in
a newline, it's squashed into the following paragraph after sorting.

The following patch fixes the problem (by adding a newline in these
cases).  Does this seems like the correct approach for everybody?

diff --git a/lisp/sort.el b/lisp/sort.el
index 6ea1c44060..6ceda8e448 100644
--- a/lisp/sort.el
+++ b/lisp/sort.el
@@ -225,11 +225,17 @@ sort-paragraphs
       (narrow-to-region beg end)
       (goto-char (point-min))
       (sort-subr reverse
-		 (function
-		  (lambda ()
-		    (while (and (not (eobp)) (looking-at paragraph-separate))
-		      (forward-line 1))))
-		 'forward-paragraph))))
+		 (lambda ()
+		   (while (and (not (eobp)) (looking-at paragraph-separate))
+		     (forward-line 1)))
+		 (lambda ()
+                   (forward-paragraph)
+                   ;; If the buffer doesn't end with a newline, add a
+                   ;; newline to avoid having paragraphs being
+                   ;; concatenated after sorting.
+                   (when (and (eobp)
+                              (not (bolp)))
+                     (insert "\n")))))))
 
 ;;;###autoload
 (defun sort-pages (reverse beg end)

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no