bug#35383: 27.0.50; Complete process of decoding Gnus group names

[Eric Abrahamsen <eric@ericabrahamsen.net>]

On 04/29/19 18:41 PM, Eli Zaretskii wrote:
>> From: Eric Abrahamsen <eric@ericabrahamsen.net>
>> Date: Sun, 28 Apr 2019 21:07:23 -0700
>> Cc: 35383@debbugs.gnu.org
>> 
>> > The goal is to have Gnus default to writing its active files in
>> > 'utf-8-emacs, unless the user has specifically requested otherwise.
>> > `nnmail-active-file-coding-system' governs the "mail" type servers, and
>> > `gnus-agent-file-coding-system' governs the agent. Currently those two
>> > options default to 'raw-text, we'd like them to default to 'utf-8-emacs.
>> 
>> Actually, maybe that's wrong. We don't care how the files are written,
>> only that, after parsing, the group names are successfully _decoded_ to
>> 'utf-8-emacs. Maybe I'm trying too hard?
>
> When you decode _any_ text by _any_ coding-system, the result is
> _always_ utf-8-emacs, because utf-8-emacs is the internal
> representation of characters and raw bytes in Emacs buffers and
> strings.

I did know that much! I'm pretty bad at encoding, but not quite that
bad.

> We write text out as utf-8-emacs when we don't want to risk the danger
> of decoding incorrectly due to local customizations and language
> environments.  Text encoded in utf-8-emacs can by definition represent
> _any_ character and raw byte that Emacs can read, and the "decoding"
> in this case is trivial.
>
> So no, you are not trying too hard, not IMO.

So you think Gnus' various *-file-coding-system options should
default to 'utf-8-emacs rather than 'raw-text?

As per your other message, it sounds like active files written as
'raw-text will probably survive being read as 'utf-8-emacs. And if the
user has previously customized those options to something else, the
change in default value won't matter anyway.

What I meant by "trying too hard" is, maybe it's enough to just change
the defaults, and not add any other error checking and guarantees?

Thanks for looking at this,
Eric