bug#74857: 30.0.92; Gnus nnatom: url protocol

[Daniel Semyonov via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

>>>>> Eli Zaretskii writes:

    >> From: Christopher Howard <christopher@librehacker.com>
    >> Date: Fri, 13 Dec 2024 10:13:02 -0900
    >> 
    >> 
    >> 
    >> Hi. When setting up a new feed group with nnatom in Gnus, there is a
    >> little oddity: If I pass in the URL to the feed without the protocol
    >> specifier, i.e., without the "https://" it works fine. But if I try
    >> to include the protocol specifier, then I get a message: "Couldn’t
    >> request list: nil", and the group is not added. It doesn't trigger
    >> the debugger, even though "debug-on-error" is set t.
    >> 
    >> So, I frequently have to delete the "https://" part when I am copying and pasting from some link for an atom feed. This is a bother.
    >> 
    >> I don't know if this can be reproduced without Gnus already being setup, but an example process is:
    >> 
    >> (1) bring up Gnus group buffer
    >> (2) run gnus-group-browse-foreign-server (B)
    >> (3) nnatom <RET>
    >> (4) https://sachachua.com/blog/category/emacs/feed/atom/ <RET>

    > Daniel, any comments or suggestions?

This is a known issue (also noted in the manual), though the message
returned should be more descriptive.

The returned message is emitted by Gnus when it fails to get info for
the server from the backend, and should use the value of
'backend-status-string' ('nnatom-status-string' in this case); this
works on a normal session on my end (returning a message set in
'nnatom--read-feed'), but fails with emacs -Q, also returning "Couldn't
request list: nil".
I half suspect this is a bug with Gnus trying to read the status string
of the wrong server (and not a bug in nnatom), but I'll look into it.

As for why it isn't allowed in the first place, Gnus unfortunately
breaks when ":" is used in server addresses due to regular expressions
used in various internal functions, though I don't remember the details.

Daniel