bug#65604: [PATCH] Display the exit code if the last command failed in Eshell

[Davide Masserut via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Jim Porter <jporterbugs@gmail.com> writes:

> Hmm, well if everyone else disagrees, I suppose I don't see any
> *major* issues with including the exit status in the prompt, though
> I'm a little worried it would annoy people who like the current
> way. If it were easier to customize the prompt, I don't think I'd be
> as worried. Fixing that for real is probably beyond the scope of 
> this
> bug, but I do have a WIP patch for it.

What do you find difficult to customize?

I can only think of two things:

1) The default function is quite simple, but displaying the bytecode 
in customization buffer can be confusing.

Hide Eshell Prompt Function: Function:
#[0 "\300\301 !\302 \303U\203\0\304\202\0\305P\207"
    [abbreviate-file-name eshell/pwd file-user-uid 0 " # " " $ "] 3]
    State : STANDARD.
   A function that returns the Eshell prompt string. Hide
   Make sure to update ‘eshell-prompt-regexp’ so that it will match 
   your
   prompt.

2) It may require to update the regexp.

Can we use rx to make it more understandable?

> If we do use the mode-line to display this though, I was initially
> thinking we could use the existing variable
> 'eshell-command-running-string', which we could set to something 
> like
> "!!" in 'eshell-command-finished'. That's not as useful as the 
> actual
> number though, and honestly I'm not sure the current
> 'eshell-status-in-mode-line' code is a good idea anyway. It
> (buffer-locally) replaces the mode-line construct immediately after
> 'mode-line-front-space', which means you lose some of the
> potentially-useful information there.
>
> Maybe it would make sense to move *all* of the current Eshell
> mode-line stuff to the 'mode-line-process' construct. That seems 
> like
> it would be less brittle. That is, in 'mode-line-process', we could
> show whether a command is running or the exit status if nothing's
> running (possibly including successful exit). What does everyone 
> think
> about that?

In this case I would add a small delay before signaling that something 
is running.

However, I'm not sure it is so useful to signaling it.
When I suspect that the process is hanging, I usually use tools like 
top or proced to check if something is stuck, but otherwise I already 
know something is going on.

I believe some terminals update the title bar when something is 
running and send a notification when process ends and the window is 
not focused.
But for such long operations compilation-mode works best for me (BTW, 
thank you for the new compile command).

>>> and OTOH Bash does show abnormal exit codes as part of its prompt.
>>> But feel free to disregard
>>> my opinions, as I'm not a heavy user of Eshell.)
>> fish and some zsh distributions also show the error in the prompt.
>
> Do they? I tried to see what the default was for Bash and after some
> searching, it seemed that it doesn't show the exit status by
> default. But that could be wrong.

Distros often change the default prompt.