Re: [Emacs-diffs] master 9ce1d38: Use curved quotes in core elisp diagnostics

[Paul Eggert]

Dmitry Gutov wrote:
> So yes, I think it's valuable.

OK, thanks for reviewing; I installed the %q patch, and followed up with 
simplifications that it allows at the C level, mostly by using %qs in formats 
instead of uLSQM and uRSQM.  This makes the C code easier to read and so is a 
clear win.  Doing something similar in Elisp code makes the code harder to read, 
though, so I held off on that.

> two format sequences, one for opening quote, and one for closing. That
> would be more cumbersome, though.

Yes, it would be more cumbersome.  Instead of the current:

  (message "Press ‘?’ or ‘h’ for help, ‘q’ to quit")

we would have something like:

  (message "Press %<?%> or %<h%> for help, %<q%> to quit")

which is harder to read and is more error-prone.  This less-readable approach is 
used in GCC's source code, which must port to old-fashioned C++ compilers that 
lack support for multibyte characters in strings.  It is not needed for Emacs 
Lisp, and we shouldn't insist on it there.

> > Also, it wouldn't suffice for code like this:
>  >
> >      (insert (symbol-name type)
> >              (format " is a type (of kind ‘"))
> >      (help-insert-xref-button (symbol-name metatype)
> >                               'cl-help-type metatype)
> >      (insert (format "’)"))
>
> But this is not about diagnostic messages anymore, right? At the moment, IIRC,
> these situations are handled by substitute-command-keys (and there's no need to
> have curly quotes in the strings here).

At the moment these situations are handled by ‘format’.  Simply changing the 
code to use ‘substitute-command-keys’ and ASCII characters would not work in 
cases like the above, because (insert (substitute-command-keys "')")) would 
insert an apostrophe regardless of user text-quoting preference.  Of course 
there are workarounds but the workarounds are clumsy.  (Also, the 
ASCII-only-source approach would typically be a tad slower, which is annoying. :-)

> text -> (substitute-command-keys) -> text with "escaped" text prop
>       -> (translate-quotes) -> text with non-escaped straight quotes replaces

As mentioned above it's not obvious how to get that to work; even if we did so 
it'd be more complicated and error-prone, and a bit slower.  Hardly seems worth it.