GNU bug report logs - #54136
29.0.50; Eshell emits extra prompts when killing processes in some cases

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Jim Porter <jporterbugs <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 29.0.50; Eshell emits extra prompts when killing processes in some
 cases
Date: Wed, 23 Feb 2022 21:11:41 -0800

(Patch forthcoming; I'm just getting a bug number first...)

Sometimes, when killing processes in Eshell (especially in pipelines), 
Eshell will emit *two* prompts instead of one. Starting with "emacs -Q 
--eval '(eshell)'...

Problem #1: Killing pipelines
-----------------------------

  ~ $ sh -c 'while true; do echo y; sleep 1; done' | sh -c 'while true; 
do read NAME; done'
  C-c C-c  ; or C-c C-k

The result is ("|" is the point):

  interrupted
  ~ $
  ~ $ |

What's happening here is one prompt is being emitted per process in the 
pipeline. It should only emit one prompt total.


Problem #2: Killing the head of a pipeline
------------------------------------------

  ~ $ sh -c 'while true; do sleep 1; done' | sh -c 'while read NAME; do 
echo =${NAME}=; done'
  M-: (kill-process (eshell-head-process)) RET

The result is:

  ~ $ =killed=
  |

In this case, Eshell writes the head process's exit status message to 
its stdout handle (i.e. to the tail process's stdin). It should either 
write directly to the terminal, or not write at all. I went with the 
latter, since the former would mean that we write "interrupted" N times 
in problem #1 above.


Problem #3: Killing a background process
----------------------------------------

   ~ $ sh -c 'while true; do sleep 1; done' &

This outputs, as expected:

  [sh] 12345
  ~ $

Now call `(kill-process (caar eshell-process-list))'. The result is:

  ~ $ killed
  ~ $ |

Here, Eshell writes the exit status to the terminal, but does so in an 
awkward spot, and then emits a new prompt. I think it should just avoid 
printing anything here. Information about the killed process is also 
shown in the minibuffer, so the user already has a place (and a better 
one at that!) to see what happened.

Message #8 received at 54136 <at> debbugs.gnu.org (full text, mbox):

From: Jim Porter <jporterbugs <at> gmail.com>
To: 54136 <at> debbugs.gnu.org
Subject: Re: bug#54136: 29.0.50; Eshell emits extra prompts when killing
 processes in some cases
Date: Wed, 23 Feb 2022 21:16:04 -0800

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

On 2/23/2022 9:11 PM, Jim Porter wrote:
> (Patch forthcoming; I'm just getting a bug number first...)

Ok, here's the patch with some tests.

[0001-Don-t-superfluously-emit-prompts-when-terminating-pr.patch (text/plain, attachment)]

Message #11 received at 54136 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Jim Porter <jporterbugs <at> gmail.com>
Cc: 54136 <at> debbugs.gnu.org
Subject: Re: bug#54136: 29.0.50; Eshell emits extra prompts when killing
 processes in some cases
Date: Thu, 24 Feb 2022 10:35:32 +0100

Jim Porter <jporterbugs <at> gmail.com> writes:

> Ok, here's the patch with some tests.

Thanks; pushed to Emacs 29.

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

Message #16 received at 54136 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: 54136 <at> debbugs.gnu.org, jporterbugs <at> gmail.com
Subject: Re: bug#54136: 29.0.50;
 Eshell emits extra prompts when killing processes in some cases
Date: Thu, 24 Feb 2022 13:03:36 +0200

> From: Lars Ingebrigtsen <larsi <at> gnus.org>
> Date: Thu, 24 Feb 2022 10:35:32 +0100
> Cc: 54136 <at> debbugs.gnu.org
> 
> Jim Porter <jporterbugs <at> gmail.com> writes:
> 
> > Ok, here's the patch with some tests.
> 
> Thanks; pushed to Emacs 29.

The new tests fail on MS-Windows.  Does the patch below look right?
I'm quite sure about the "sh" vs "sh.exe" part, but what about the
"killed" vs "interrupt" part? any idea why this happens on MS-Windows?

diff --git a/test/lisp/eshell/esh-proc-tests.el b/test/lisp/eshell/esh-proc-tests.el
index a8be0f8..3f67961 100644
--- a/test/lisp/eshell/esh-proc-tests.el
+++ b/test/lisp/eshell/esh-proc-tests.el
@@ -59,7 +59,7 @@ esh-proc-test/kill-pipeline
      (eshell-wait-for-subprocess t)
      (should (equal (buffer-substring-no-properties
                      output-start (eshell-end-of-output))
-                    "killed\n")))))
+                    (or "interrupt\n" "killed\n"))))))
 
 (ert-deftest esh-proc-test/kill-pipeline-head ()
   "Test that killing the first process in a pipeline doesn't
@@ -88,4 +88,4 @@ esh-proc-test/kill-background-process
    (kill-process (caar eshell-process-list))
    ;; Give `eshell-sentinel' a chance to run.
    (sit-for 0.1)
-   (eshell-match-result "\\[sh\\] [[:digit:]]+\n")))
+   (eshell-match-result "\\[sh\\(\\.exe\\)?\\] [[:digit:]]+\n")))

Message #19 received at 54136 <at> debbugs.gnu.org (full text, mbox):

From: Jim Porter <jporterbugs <at> gmail.com>
To: Eli Zaretskii <eliz <at> gnu.org>, Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: 54136 <at> debbugs.gnu.org
Subject: Re: bug#54136: 29.0.50; Eshell emits extra prompts when killing
 processes in some cases
Date: Thu, 24 Feb 2022 10:55:48 -0800

On 2/24/2022 3:03 AM, Eli Zaretskii wrote:
>> From: Lars Ingebrigtsen <larsi <at> gnus.org>
>> Date: Thu, 24 Feb 2022 10:35:32 +0100
>> Cc: 54136 <at> debbugs.gnu.org
>>
>> Thanks; pushed to Emacs 29.
> 
> The new tests fail on MS-Windows.  Does the patch below look right?

Thanks, and sorry for the breakage.

> I'm quite sure about the "sh" vs "sh.exe" part, but what about the
> "killed" vs "interrupt" part? any idea why this happens on MS-Windows?

I think this makes sense. POSIX-style signal handling on MS Windows is 
only approximate, so I'm not surprised it produces some surprising 
results like that. Maybe it's possible to pass the signal code through 
the process exit status more accurately, but that's probably only a 
partial solution at best (due to the API differences), and at worst 
could break Emacs's subprocess handling for MS Windows in subtle ways.

Another solution would be to replace the call to `eshell-kill-process' 
in `esh-proc-test/kill-pipeline' with `eshell-interrupt-process'. Then 
the exit status should be "interrupt\n" on all platforms. I've verified 
that that works ok on GNU/Linux, but it's possible that it runs into 
some other issue on MS Windows.

This is sort of just working around the issue, but I also think there's 
an argument that `eshell-interrupt-process' is the more "natural" 
function to call, since it corresponds to a user hitting ^C in the shell 
(or C-c C-c in Eshell).

Message #22 received at 54136 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Jim Porter <jporterbugs <at> gmail.com>
Cc: 54136 <at> debbugs.gnu.org, larsi <at> gnus.org
Subject: Re: bug#54136: 29.0.50; Eshell emits extra prompts when killing
 processes in some cases
Date: Thu, 24 Feb 2022 22:03:36 +0200

> Cc: 54136 <at> debbugs.gnu.org
> From: Jim Porter <jporterbugs <at> gmail.com>
> Date: Thu, 24 Feb 2022 10:55:48 -0800
> 
> > I'm quite sure about the "sh" vs "sh.exe" part, but what about the
> > "killed" vs "interrupt" part? any idea why this happens on MS-Windows?
> 
> I think this makes sense. POSIX-style signal handling on MS Windows is 
> only approximate, so I'm not surprised it produces some surprising 
> results like that. Maybe it's possible to pass the signal code through 
> the process exit status more accurately, but that's probably only a 
> partial solution at best (due to the API differences), and at worst 
> could break Emacs's subprocess handling for MS Windows in subtle ways.
> 
> Another solution would be to replace the call to `eshell-kill-process' 
> in `esh-proc-test/kill-pipeline' with `eshell-interrupt-process'. Then 
> the exit status should be "interrupt\n" on all platforms. I've verified 
> that that works ok on GNU/Linux, but it's possible that it runs into 
> some other issue on MS Windows.
> 
> This is sort of just working around the issue, but I also think there's 
> an argument that `eshell-interrupt-process' is the more "natural" 
> function to call, since it corresponds to a user hitting ^C in the shell 
> (or C-c C-c in Eshell).

OK, so I installed my changes.

Thanks.

Message #25 received at 54136 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 54136 <at> debbugs.gnu.org, Jim Porter <jporterbugs <at> gmail.com>
Subject: Re: bug#54136: 29.0.50; Eshell emits extra prompts when killing
 processes in some cases
Date: Thu, 24 Feb 2022 21:07:29 +0100

Eli Zaretskii <eliz <at> gnu.org> writes:

> OK, so I installed my changes.

The test now fails on Debian:

Test esh-proc-test/kill-pipeline condition:
    (ert-test-failed
     ((should
       (equal
	(buffer-substring-no-properties output-start ...)
	(or "interrupt\n" "killed\n")))
      :form
      (equal "killed\n" "interrupt\n")
      :value nil :explanation
      (arrays-of-different-length 7 10 "killed\n" "interrupt\n" first-mismatch-at 0)))
   FAILED  2/4  esh-proc-test/kill-pipeline (0.109668 sec) at lisp/eshell/esh-proc-tests.el:47
   passed  3/4  esh-proc-test/kill-pipeline-head (0.112142 sec)
   passed  4/4  esh-proc-test/sigpipe-exits-process (1.010359 sec)

Ran 4 tests, 3 results as expected, 1 unexpected (2022-02-24 21:06:48+0100, 1.446135 sec)

1 unexpected results:
   FAILED  esh-proc-test/kill-pipeline

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

Message #28 received at 54136 <at> debbugs.gnu.org (full text, mbox):

From: Jim Porter <jporterbugs <at> gmail.com>
To: Lars Ingebrigtsen <larsi <at> gnus.org>, Eli Zaretskii <eliz <at> gnu.org>
Cc: 54136 <at> debbugs.gnu.org
Subject: Re: bug#54136: 29.0.50; Eshell emits extra prompts when killing
 processes in some cases
Date: Thu, 24 Feb 2022 17:04:42 -0800

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

On 2/24/2022 12:07 PM, Lars Ingebrigtsen wrote:
> Eli Zaretskii <eliz <at> gnu.org> writes:
> 
>> OK, so I installed my changes.
> 
> The test now fails on Debian:
> 
> Test esh-proc-test/kill-pipeline condition:
>      (ert-test-failed
>       ((should
>         (equal
> 	(buffer-substring-no-properties output-start ...)
> 	(or "interrupt\n" "killed\n")))
>        :form
>        (equal "killed\n" "interrupt\n")
>        :value nil :explanation
>        (arrays-of-different-length 7 10 "killed\n" "interrupt\n" first-mismatch-at 0)))
>     FAILED  2/4  esh-proc-test/kill-pipeline (0.109668 sec) at lisp/eshell/esh-proc-tests.el:47
>     passed  3/4  esh-proc-test/kill-pipeline-head (0.112142 sec)
>     passed  4/4  esh-proc-test/sigpipe-exits-process (1.010359 sec)
> 
> Ran 4 tests, 3 results as expected, 1 unexpected (2022-02-24 21:06:48+0100, 1.446135 sec)
> 
> 1 unexpected results:
>     FAILED  esh-proc-test/kill-pipeline

Here's a patch for that. It works for me on GNU/Linux, and hopefully 
it's ok on MS Windows too.

[0001-Fix-Eshell-process-tests-to-hopefully-work-on-all-pl.patch (text/plain, attachment)]

Message #31 received at 54136 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Jim Porter <jporterbugs <at> gmail.com>
Cc: 54136 <at> debbugs.gnu.org, Eli Zaretskii <eliz <at> gnu.org>
Subject: Re: bug#54136: 29.0.50; Eshell emits extra prompts when killing
 processes in some cases
Date: Fri, 25 Feb 2022 03:18:52 +0100

Jim Porter <jporterbugs <at> gmail.com> writes:

> Here's a patch for that. It works for me on GNU/Linux, and hopefully
> it's ok on MS Windows too.

Thanks; pushed to the trunk.

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

Message #34 received at 54136 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Jim Porter <jporterbugs <at> gmail.com>
Cc: 54136 <at> debbugs.gnu.org, larsi <at> gnus.org
Subject: Re: bug#54136: 29.0.50; Eshell emits extra prompts when killing
 processes in some cases
Date: Fri, 25 Feb 2022 09:09:36 +0200

> Cc: 54136 <at> debbugs.gnu.org
> From: Jim Porter <jporterbugs <at> gmail.com>
> Date: Thu, 24 Feb 2022 17:04:42 -0800
> 
> On 2/24/2022 12:07 PM, Lars Ingebrigtsen wrote:
> > Eli Zaretskii <eliz <at> gnu.org> writes:
> > 
> >> OK, so I installed my changes.
> > 
> > The test now fails on Debian:
> > 
> > Test esh-proc-test/kill-pipeline condition:
> >      (ert-test-failed
> >       ((should
> >         (equal
> > 	(buffer-substring-no-properties output-start ...)
> > 	(or "interrupt\n" "killed\n")))
> >        :form
> >        (equal "killed\n" "interrupt\n")
> >        :value nil :explanation
> >        (arrays-of-different-length 7 10 "killed\n" "interrupt\n" first-mismatch-at 0)))
> >     FAILED  2/4  esh-proc-test/kill-pipeline (0.109668 sec) at lisp/eshell/esh-proc-tests.el:47
> >     passed  3/4  esh-proc-test/kill-pipeline-head (0.112142 sec)
> >     passed  4/4  esh-proc-test/sigpipe-exits-process (1.010359 sec)
> > 
> > Ran 4 tests, 3 results as expected, 1 unexpected (2022-02-24 21:06:48+0100, 1.446135 sec)
> > 
> > 1 unexpected results:
> >     FAILED  esh-proc-test/kill-pipeline
> 
> Here's a patch for that. It works for me on GNU/Linux, and hopefully 
> it's ok on MS Windows too.

Thanks, and sorry for the thinko.  (I thought posting the patch would
have that caught, but I guess no one reads my patches seriously.)

Message #37 received at 54136 <at> debbugs.gnu.org (full text, mbox):

From: Jim Porter <jporterbugs <at> gmail.com>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 54136 <at> debbugs.gnu.org, larsi <at> gnus.org
Subject: Re: bug#54136: 29.0.50; Eshell emits extra prompts when killing
 processes in some cases
Date: Fri, 25 Feb 2022 10:31:45 -0800

On 2/24/2022 11:09 PM, Eli Zaretskii wrote:
>> Here's a patch for that. It works for me on GNU/Linux, and hopefully
>> it's ok on MS Windows too.
> 
> Thanks, and sorry for the thinko.  (I thought posting the patch would
> have that caught, but I guess no one reads my patches seriously.)

Indeed, sorry about that. I spent an hour reading the Emacs's C sources 
and digging through Microsoft docs on subprocesses to try and understand 
why the exit message differed, but neglected the obvious step of "read 
the actual patch". D'oh.

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