bug#53715: 29.0.50; [PATCH] Improve correctness of pipelines in Eshell

[Jim Porter]

On 2/3/2022 11:03 AM, Lars Ingebrigtsen wrote:
> Jim Porter <jporterbugs@gmail.com> writes:
>
> > Here's a small additional improvement that I hope is correct. The
> > third patch here changes how eshell-tests-helpers.el is loaded to that
> > it uses `require'. This reduces some of the boilerplate and will
> > hopefully prevent issues with this file not getting recompiled when
> > it's updated.
> >
> > The first two patches are the same as before. I've just included them
> > for completeness/ease of applying.
>
> Thanks; seems to work well for me, so I've now pushed them to Emacs 29.

I found a bug in the second patch.

  emacs -Q --eval '(eshell)'
  ~ $ echo hi | *cat

This prints:

  ~ $ hi

That is, the output of the command is printed *after* the next prompt. 
That's because my patch wasn't smart enough about finding the "head" 
process in a pipeline. In "echo hi | *cat", the head process is "cat" 
(Eshell's builtin echo command doesn't create a process). In my old 
patch, it thought the head process was nil, which confused Eshell.

Here's a patch with a test to verify that things work correctly. Now the 
output is:

  hi~ $

(That's a bit ugly, but Eshell's builtin echo doesn't normally print a 
newline, so it's correct.)

0001-Ensure-that-the-CAR-of-eshell-last-async-procs-alway.patch
Description: Text document