Re: custom-set-variables considered harmful

[Eli Zaretskii]

> From: Stefan Monnier <address@hidden>
> Date: Mon, 04 Dec 2017 08:48:06 -0500
> 
> Based on the feedback, I added a config var to control the use of `setq'.
> I also added a backward compatibility hack which makes it so that your
> "new style config" will partly work in Emacs<27.

Thanks.

> Any objection to installing the patch below into `master`?

No objections from me, but:

 . please add :version tags to defcustoms
 . please add some documentation, including a NEWS entry

A couple of nits about doc strings below.

> +(defcustom custom-mimic-plain-elisp nil
> +  "If non-nil, save user settings with the new format.

IME, saying "new" in documentation is not a very good idea: it conveys
no useful information, and after some time it is no longer "new".  How
about something like the below?

  If non-nil, save user settings using format that mimics hand-written code.

Then you could lose the next sentence of the doc string:

> +This new format tries to mimick the code that would be written by hand
> +in plain Elisp.

> +                 But it relies on `custom-autogenerated-user-settings' which
> +is a new macro in Emacs-27, so settings saved with this will not work
> +reliably in Emacs<27 (although a backward compatibility trick is used
> +which should make them work to some extent)."

This sounds like a comment, not sure if it will be useful to users.

> +(defcustom custom-mimic-plain-elisp-use-setq nil
> +  "If non-nil, use `setq' when possible in generated code.

I'd suggest "in code generated by `custom-mimic-plain-elisp'".

> +(defmacro custom-autogenerated-user-settings (&rest body)
> +  "Install user customizations of variable values specified in ARGS.

Ehm... which "ARGS" are those?  There's just BODY.