bug#22335: 24.2; Documentation of shell-command-on-region incorrect?

[Eli Zaretskii <eliz@gnu.org>]

> Date: Fri, 08 Jan 2016 19:44:11 -0800
> From: Paul Hilfinger <hilfingr@eecs.berkeley.edu>
> 
> The current documentation for shell-command-on-region says that 
> 
>     If the optional fourth argument OUTPUT-BUFFER is non-nil,
>     that says to put the output in some other buffer.
>     If OUTPUT-BUFFER is a buffer or buffer name, put the output there.
>     If OUTPUT-BUFFER is not a buffer and not nil,
>     insert output in the current buffer.
>     In either case, the output is inserted after point (leaving mark after it).
> 
>     If REPLACE, the optional fifth argument, is non-nil, that means insert
>     the output in place of text from START to END, putting point and mark
>     around it.
> 
> This seems to suggest that if REPLACE is nil, the initial contents of
> OUTPUT-BUFFER are retained.  However, this does not seem to be the
> behavior of the command at all.  Indeed, in the defun for
> shell-command-on-region, there appears:
> 
>     (if (or replace
> 	    (and output-buffer
> 		 (not (or (bufferp output-buffer) (stringp output-buffer)))))
> 	;; Replace specified region with output from command.
> 	(let ((swap (and replace (< start end))))
> 	  ;; Don't muck with mark unless REPLACE says we should.
> 	  (goto-char start)
> 	  (and replace (push-mark (point) 'nomsg))
> 	  (setq exit-status
> 		(call-process-region start end shell-file-name t
> 				     (if error-file
> 					 (list t error-file)
> 				       t)
> 				     nil shell-command-switch command))
> 
> which would indeed seem to delete the existing text unconditionally.

The argument 't' to call-process-region was changed to 'replace' in
Emacs 24.4, so this appears to be fixed already.  I suggest to upgrade
to a newer Emacs version.

Thanks.