bug#26161: 25.1; `eshell-exit-success-p' determines that Lisp commands are successful if they return non-nil

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"George D. Plymale" <georgedp@orbitalimpact.com> writes:

> it'd probably be better off if `eshell-exit-success-p' just
> checked`eshell-last-command-status' and Eshell makes sure that erring commands
> always set that to non-zero (which I think is already covered by
> `eshell-trap-errors').

That makes sense to me.

>> AFAICT, when you cd to a non-existent directory it doesn't throw an
>> error, but I don't think that should be considered success.
>
> Yeah, `eshell/cd' actually is able to bypass something like
> `eshell-trap-errors' because it uses `cd' under the hood through this
> function invocation: `(eshell-printn result)' where `result' is `(cd
> newdir)'. See, `eshell-printn' just captures the result of its given
> object and prints that out. In some cases, that object is an error (like
> when you cd into a non-existent directory), but you can't really tell
> that because `eshell-printn' doesn't care about errors; it just prints
> out the object it's given. Functions that do this sort of thing may also
> exist aside from `eshell/cd', so I'm unsure what can be done about that.

It looks like `eshell-exec-lisp' catches the error, so probably
`eshell-last-command-status' could be set there.  Patches welcome.