bug#49518: 28.0.50; electric-pair-mode skip-self fails for single-quotes in python-mode

[Jim Porter <jporterbugs@gmail.com>]

On 9/18/2021 5:20 PM, João Távora wrote:
> So after having a look at this, I came up with a patch.  All tests
> pass, and your original request is granted.  Unfortunately, Stephen's
> desired triple-pair behaviour is also lost.  However, I think that
> behaviour can be recovered via other more elegant, less accidental ways.
> python.el has 'python-electric-pair-string-delimiter' for triple-pairing
> that doesn't seem to be doing its thing.
> 
> Here is the patch.  Give it a shot.
> 
> diff --git a/lisp/elec-pair.el b/lisp/elec-pair.el
> index d8c377a2ef..b8b8a97651 100644
> --- a/lisp/elec-pair.el
> +++ b/lisp/elec-pair.el
> @@ -198,7 +198,9 @@ electric-pair-syntax-info
>   inside a comment or string."
>     (let* ((pre-string-or-comment (or (bobp)
>                                       (nth 8 (save-excursion
> -                                             (syntax-ppss (1- (point)))))))
> +                                             (skip-chars-backward
> +                                              (make-string 1 command-event))
> +                                             (syntax-ppss (point))))))
>            (post-string-or-comment (nth 8 (syntax-ppss (point))))
>            (string-or-comment (and post-string-or-comment
>                                    pre-string-or-comment))
> 

Thanks, this patch works for me. It also works fine with my patch in 
bug#50538, so there's no conflict there.

> Maybe better less brittle solutions can probably be found within the
> syntax tables framework.

I agree that something less brittle would be nice, but that might be 
tricky. I had tried a few options when I filed this bug, but nothing 
worked quite right.

As for Stephen's desired behavior, the code snippet I posted above[1] 
mostly fixes it (just the `python-electric-pair-string-delimiter' part 
is necessary after your patch). However, that code doesn't work right if 
`electric-pair-skip-self' is set to nil, so I'd need to be a bit smarter 
with the implementation if I wanted to merge it into Emacs. Perhaps 
there's an even cleaner solution though.

[1] https://lists.gnu.org/archive/html/bug-gnu-emacs/2021-09/msg01509.html