bug#19822: url-retrieve: allow to fail when no document is associated with the URI

[Stefan Kangas <stefan@marxist.se>]

Lars Ingebrigtsen <larsi@gnus.org> writes:

> Ivan Shmakov <ivan@siamics.net> writes:
>
>> The handling of the news: (nntp:), irc:, and (as it seems) ftp:
>> (file:) URI schemes is implemented in such a way that a
>> /successful/ url-retrieve call is /not/ in fact guaranteed to
>> return a “retrieved document” of any kind.  Consider, e. g.:
>>
>> (let ((url-proxy-services nil))
>> (list (url-retrieve "news://news.aioe.org/alt.sources"
>> (lambda (&rest any) (message "news: %S" any)))
>> (url-retrieve "irc://irc.freenode.net:6667/x-test-channel"
>> (lambda (&rest any) (message "irc:  %S" any)))))
>>
>> Here, the first call starts up Gnus and opens a *Summary* buffer
>> for the group; the second starts Rcirc by default; either call
>> returns nil.
>
> I think all these non-http{s,} things in the URL library should be
> marked obsolete and removed.  There is very little utility to them (some
> have been broken for years without anybody noticing), and they are very
> fiddly to maintain.
>
> Anybody mind if I remove them for Emacs 25.2?

Hi Lars,

This is a good idea, but it seems like it was never done?  There was
no one protesting the proposal at the time (December 2015).  Perhaps
we should move some of them to obsolete/ before Emacs 27.1?

Best regards,
Stefan Kangas