bug#38955: 27.0.50; message-send-mail fails on non-printable characters in header

[Lars Ingebrigtsen <larsi@gnus.org>]

Pieter van Oostrum <pieter@vanoostrum.org> writes:

> 1) Reply to the attached email message in gnus.
> 2) Send the message (C-c C-c)
>
> Emacs gives an error
> cl--assertion-failed: Assertion failed: (save-excursion (goto-char (point-min)) (not (re-search-forward "[^.-ÿ]" nil t)))
> which isn't helpful at all.

[...]

> The error is caused by a header with unprintable characters. The raw header is:
> To: =?iso-8859-1?Q?=E7=A9=8D=E4=B8=B9=E5=B0=BC?= Dan Jacobson
>  <jidanni@jidanni.org>
> which translates to unprintable characters.

[...]

> I propose that the same choice is given to the user when these
> characters appear in the header. This means the test should also be
> done in message-fix-before-sending().

I've now done this in Emacs 28.

> Another suggestion: Can an additional choice be given to replace the
> offending characters with an escaped representation, for example url
> encoding?

Yeah, that makes sense.  Perhaps URL encoding is the most widely
understood (i.e., %hex for the byte).

-- 
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   bloggy blog: http://lars.ingebrigtsen.no