bug#5742: Customize and obsolete options

[Jens Lechtenboerger]

On 2010-03-19, at 20:44, Glenn Morris wrote:

> Severity: wishlist
>
> Customize does not seem to indicate in any way when options are
> obsolete.
> [...]

I'd like to extend the reported issue.

Customize does not warn users of obsolete options.  This is
guaranteed to create surprises far in the future when the obsolete
feature is removed.  This is particularly bad, if no equivalent
functionality exists (or if it is not documented).  See bug#26233
for an example.

The functions custom-set-variables and customize-set-variable could
print warnings when they modify obsolete variables.

Even better, code that touches obsolete variables could generate
warnings.

Best wishes
Jens