puni-backward-delete-char should splice when the list around point is empty

[daanturo]

Instead of not doing anything, puni-backward-delete-char should splice the sexp around point when the delimiters are next to each other.

(|)
;; calls `puni-backward-delete-char`

;; Observed:
|()

;; Expected:
|

Currently, puni-mode-map doesn't provide any key bindings to delete the pair, the shortest I have found (without additional bindings) is backspace delete delete: 3 key presses.

[AmaiKinono]

Ah, I think electric-pair-mode is doing the job for me (I've been using it from day 1), so I haven't noticed that Puni didn't implement this.

I've seen your PR (thanks!). It's great but I'm mainly worried about multi-char delimiters. For example, in HTML (with your patch):

<p>|</p>
;; Call `puni-backward-delete-char
(nothing left)

To me this is actually reasonable but I think some people may just want this:

<p|></p>

This may because in Lisp, they are used to press DEL to go backward in opening parentheses. I sometimes do that myself.

I'm thinking if this can happens to keyword delimiters, and I found in sh-mode:

if|fi
# Call `puni-backward-delete-char`
(nothing left)

This is a surprise, though it's a corner case.

So, to me it's better to limit this behavior to single-char delimiters. What do you think?

[daanturo]

Yes, I think that the behavior for multi-char delimiters is debatable and hard to define correctly, too. So let's limit it for now.

[AmaiKinono]

I've modified it a bit and it now it deals with the multi-char delimiter case. This is because I do like it, and by switching the order of conditional branches, the if|fi problem is gone.