GNU bug report logs - #15494
[PATCH] 24.3.50; Processes running under TRAMP can't cleanly write to the middle of a buffer

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Michael Albinus <michael.albinus <at> gmx.de>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#15494: closed ([PATCH] 24.3.50; Processes running under TRAMP
 can't cleanly write to the middle of a buffer)
Date: Wed, 24 Feb 2016 06:56:02 +0000

[Message part 1 (text/plain, inline)]

Your message dated Wed, 24 Feb 2016 07:55:27 +0100
with message-id <87povmtx5s.fsf <at> gmx.de>
and subject line Re: bug#15494: [PATCH] 24.3.50; Processes running under TRAMP can't cleanly write to the middle of a buffer
has caused the debbugs.gnu.org bug report #15494,
regarding [PATCH] 24.3.50; Processes running under TRAMP can't cleanly write to the middle of a buffer
to be marked as done.

(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)


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[Message part 2 (message/rfc822, inline)]

From: Dima Kogan <dima <at> secretsauce.net>
To: bug-gnu-emacs <at> gnu.org
Subject: [PATCH] 24.3.50;
 Processes running under TRAMP can't cleanly write to the middle of a
 buffer
Date: Mon, 30 Sep 2013 00:35:04 -0700

[Message part 3 (text/plain, inline)]

Hi.

I am observing that processes running over TRAMP overwrite all the
buffer contents after (point). This is irrelevant in the usual case
where the process output is going to the end of the buffer (there's
nothing after the point in that case). This is also something that works
fine with local (i.e. non-TRAMP) processes.

To be clear, an example emacs invocation appears below. This populates
the *scratch* buffer with

a b c
1 2 3

Then moves the point to the begging of the "1 2 3" line, and runs a
TRAMP process to insert the text "inserted". I would expect the
*scratch* buffer to end up with

a b c
inserted
1 2 3

If the process runs without TRAMP, this is indeed what happens. With
TRAMP, however, I get

a b c
inserted

Note that with TRAMP the "1 2 3" line got deleted. The example invocation:


 $ emacs -Q \
   --eval \
 '(defun test-filter(process output)
         (with-current-buffer (process-buffer process) (insert output)))' \
   --eval \
 '(defun test-sentinel(process event)
         )' \
   --eval \
 '(progn
    (insert "a b c\n1 2 3\n")
    (forward-line -1)
    (cd "/sudo::/tmp")
    (let ((process (start-file-process "echo" (get-buffer "*scratch*") "echo" "inserted")))
      (set-process-sentinel process `test-sentinel)
      (set-process-filter   process `test-filter)))'


This creates a process filter that simply inserts the process output,
and a sentinel that does nothing. The (cd "/sudo::/tmp") form is there
to force the process to run with TRAMP. Every TRAMP-based path I've
tried tickles this bug for me. Removing that form makes the process run
without TRAMP, and I do not see the buggy behavior then.

I'm observing this issue with the latest emacs24 release and with the
latest emacs built from the sources as of 2013/09/30. Emacs 23.4.1
appears to NOT have this bug. This is on a machine running Debian.

I'm attaching a patch that fixes this issue for me. The cause appears to
be a bit of code that deletes the system prompt from the TRAMP output.
There's a bug in that code that deletes more than just the prompt in the
case described above.

[0001-TRAMP-processes-no-longer-delete-their-buffer-conten.patch (text/x-diff, attachment)]

[Message part 5 (message/rfc822, inline)]

From: Michael Albinus <michael.albinus <at> gmx.de>
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: 15494-done <at> debbugs.gnu.org, Dima Kogan <dima <at> secretsauce.net>
Subject: Re: bug#15494: [PATCH] 24.3.50;
 Processes running under TRAMP can't cleanly write to the middle of a
 buffer
Date: Wed, 24 Feb 2016 07:55:27 +0100

Lars Ingebrigtsen <larsi <at> gnus.org> writes:

Hi,

>> I'm attaching a patch that fixes this issue for me. The cause appears to
>> be a bit of code that deletes the system prompt from the TRAMP output.
>> There's a bug in that code that deletes more than just the prompt in the
>> case described above.
>
> The patch makes sense to me.  Michael?

I'm very sorry, but I've overlooked this bug report completely :-(

Fortunately, there was another bug report #16120, which speaks about the
same problem. And the solution is identical to what Dima proposed. It
was merged into the Emacs sources back in February 2014.

I'm closing this bug.

Best regards, Michael.

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