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.)