Re: What does `undecided' do for encoding text?

[Eli Zaretskii]

> From: Kenichi Handa <address@hidden>
> CC: address@hidden
> Date: Tue, 10 Feb 2009 16:01:10 +0900
> 
> In article <address@hidden>, Eli Zaretskii <address@hidden> writes:
> 
> > It looks like `undecided' works the same as `raw-text' for encoding
> > text.  Is that true in general?
> 
> Yes.  More exactly, it is the same as `raw-text-unix'.

Thanks.

> > I think this should be reflected in the ELisp manual.
> 
> I don't think so because it is just a fallback behavior, and
> Elisp programmer should avoid specifying `undecided' on
> encoding.

This may have nothing to do with what the programmer did.  My use case
was in Rmail: if the original message had non-ASCII text encoded with
QP or B64, Rmail would (correctly) return `undecided' when it detects
the message encoding.  Suppose you then edit the message and add
non-ASCII characters as raw bytes, e.g. by base64-decode-region, and
type "C-c C-c".  rmail-cease-edit now needs to encode the text and put
it back into the mbox buffer, and the immediate choice it has for the
pertinent coding-system is to use buffer-file-coding-system of the
buffer where the message was edited.  But the value of
buffer-file-coding-system in that buffer is `undecided'...

If you say that using `undecided' in encoding is ``considered
harmful'', we should at least say that in the ELisp manual.  Although
in the use case I described `undecided' did exactly what's right, and
the only other correct choice is `raw-text'.