bug#24759: 25.1.50; electric-quote-mode

[Eli Zaretskii <eliz@gnu.org>]

> Cc: 24759@debbugs.gnu.org
> From: Paul Eggert <eggert@cs.ucla.edu>
> Date: Fri, 21 Oct 2016 14:04:56 -0700
> 
> On 10/21/2016 12:58 PM, Eli Zaretskii wrote:
> > I think this condition:
> >
> >    (defun electric--insertable-p (string)
> >      (or (not buffer-file-coding-system)
> > 	(eq (coding-system-base buffer-file-coding-system) 'undecided)
> > 	(not (unencodable-char-position nil nil buffer-file-coding-system
> > 					nil string))))
> >
> > should also accept a coding-system that is the default-value of
> > buffer-file-coding-system, because that's how buffers are created.
> > When the file is saved, Emacs will ask for a proper encoding, which is
> > not a catastrophe.
> 
> Wouldn't this lead to problems? If I use electric quoting in a unibyte 
> French locale, where I the default is an ISO 8859 encoding and 
> buffer-file-coding-system is something like iso-latin-1-unix, when I 
> later save the file Emacs will say "Select coding system (default 
> chinese-iso-8bit): ". This is hardly user-friendly, even if we improve 
> Emacs to guess UTF-8, as there may be a long interval between typing ` 
> and saving the buffer.

This is standard Emacs behavior.  Emacs never makes any tests of the
current buffer-file-coding-system when you insert characters.  You
will see the same at save-buffer time if you insert the curved quotes
with, e.g., "C-x 8 [", where we insert the character no matter what is
the current buffer-file-coding-system.  Users who use
electric-quote-mode and don't have UTF-8 as their default encoding
will get accustomed to this prompt soon enough.

So I actually question the need for any test in electric--insertable-p.
What bad things, besides the prompt at save-buffer time, will happen
if we remove the test, and insert the characters unconditionally?