bug#8857: display-buffer attempt to pop-up frame in batch mode causes "Unknown terminal type" error

[Glenn Morris]

martin rudalics wrote:

>> OK, this is not a very sensible example, but it illustrates the point.
>> It's caused by display-buffer trying to pop-up a frame in batch-mode and
>> is very recent.
>
> Can you tell me where and why `display-buffer' is called?

I don't know. From `find-file' I guess. I noticed because of this:

http://lists.gnu.org/archive/html/emacs-buildstatus/2011-06/msg00004.html

(which was due to custom-make-dependencies leaving files on the
command-line so they were processed as normal file arguments)

>> PS I forgot to say that I think display-buffer should not try to pop-up
>> frames (or do anything at all?) in batch-mode. Or if it must give an
>> error it should try to give a more helpful one than "Unknown terminal
>> type".
>
> In particular not with emacs -Q.  But I have no experience debugging
> emacs with the batch option.  So before delving into this maybe you
> could give me more information?

Maybe display-buffer should just be a no-op in batch-mode, since it's
impossible (?) to display anything then (except via the echo area).

(defun display-buffer () ""
 (unless noninteractive
   ...))