Re: Using utf-8-auto as a process coding system

[Eli Zaretskii <eliz@gnu.org>]

> Date: Tue, 22 Jul 2014 08:55:53 +0300
> From: Bozhidar Batsov <bozhidar.batsov@gmail.com>
> Cc: schwab@suse.de, emacs-devel@gnu.org
> 
> Ops, I actually used an incorrect link. That’s the proper one - https://github.com/clojure-emacs/cider/issues/532

OK, but that one is very short ;-)

> The gist of my problem is that Windows users have encoding related problems running cider (discussion here https://github.com/clojure-emacs/cider/issues/474).

There's a lot of confusion in that discussion.

> I guess the problem stems from this bit of code: 
> 
> (set-process-coding-system process 'utf-8-unix 'utf-8-unix)

'-auto' is not about end-of-line (EOL) format, it is about the Byte
Order Mark BOM (http://en.wikipedia.org/wiki/Byte_order_mark).

Does Cider on Windows indeed output UTF-8 encoded text preceded by a
BOM?  I'd be surprised, as the BOM is normally not needed with UTF-8.
In which case all this -auto thing just comes from another confused
user.

If there's no BOM, the first thing I'd try on Windows is this:

 (set-process-coding-system process 'utf-8-dos 'utf-8-unix)

This is because Windows programs will normally accept Unix EOL format
on input, but will usually output Windows CR-LF EOL, which Emacs needs
to decode into a single newline character.

A more elegant solution, which should be platform-independent, is to
use something like below (untested)

  (set-process-coding-system process
  			     (cons (coding-system-change-text-conversion
			            (car default-process-coding-system)
			            'utf-8)
				   (coding-system-change-text-conversion
				    (cdr default-process-coding-system)
                                    'utf-8)))

This has the advantage that it uses the wisdom already invested in
setting the defaults for each platform.