bug#54976: 29.0.50; Eshell breaks when unknown entries in eshell-modules-list

[Sean Whitton <spwhitton@spwhitton.name>]

Hello,

On Sun 19 Jun 2022 at 07:57am -07, Stefan Kangas wrote:

> close 54976 29.1
> thanks
>
> Sean Whitton <spwhitton@spwhitton.name> writes:
>
>> Suppose you put this in your init.el:
>>
>>     (add-to-list 'eshell-modules-list 'eshell-elecslash)
>>
>> because you want to use the new em-elecslash.el module I'm working on.
>>
>> Then if you try to M-x eshell on an older version of Emacs which lacks
>> em-elecslash, Eshell will fail to initialise at all.
>>
>> It is easy add a guard (when (locate-library ...)) or similar, but this
>> is not possible if you have added eshell-elecslash using the customise
>> interface.  In that case, by enabling the module, youq just make your
>> init unusable with older Emacs.
>>
>> It would be better to print a warning, say, rather than error.
>
> I agree that it makes more sense to warn here instead of refusing to
> start.  So I have now done that in Emacs 29 (commit d6b4803850).

Many thanks for this!

-- 
Sean Whitton