Implement Kakoune's A-S

[kirawi]

In Kakoune, it selects the first and last characters of each selection.

Where [] denotes a selection, [helix] becomes [h]eli[x]

It would look similar to

helix/helix-term/src/commands.rs

Lines 1855 to 1864 in 87a720c

	fn split_selection_on_newline(cx: &mut Context) {
	let (view, doc) = current!(cx.editor);
	let text = doc.text().slice(..);
	// only compile the regex once
	#[allow(clippy::trivial_regex)]
	static REGEX: Lazy<Regex> =
	Lazy::new(|| Regex::new(r"\r\n|[\n\r\u{000B}\u{000C}\u{0085}\u{2028}\u{2029}]").unwrap());
	let selection = selection::split_on_matches(text, doc.selection(view.id), &REGEX);
	doc.set_selection(view.id, selection);
	}

but use

helix/helix-core/src/selection.rs

Lines 607 to 614 in 87a720c

	pub fn transform_iter<F, I>(mut self, f: F) -> Self
	where
	F: FnMut(Range) -> I,
	I: Iterator<Item = Range>,
	{
	self.ranges = self.ranges.into_iter().flat_map(f).collect();
	self.normalize()
	}

instead

[scdailey]

Is anyone working on this one at the moment? I'd like to make my first contribution

[kirawi]

Nobody has announced that they're working on this, so it's probably fine?

[scdailey]

Cool! Ill give it a shot

[woojiq]

I'm not against this, just asking what is a usecase? The only situation I can see is something like selecting parentheses/brackets and delete them, but for that I can use existing keybinds.

[scdailey]

#9483

Just created a pull request for this one

[the-mikedavis]

Did you have something specific in mind for this command @kirawi? I also wonder if we need a command for this given that we have surround tools builtin while Kakoune does not

[kirawi]

It was requested by https://matrix.to/#/!zMuVRxoqjyxyjSEBXc:matrix.org/$bFvOW3o-qWGL_cSdJWwK1wE86NXUz8LFq7rBJtO6VMA?via=matrix.org&via=mozilla.org&via=envs.net and I thought it was simple enough (and because Kakoune included it).

mawww/kakoune#550 is the issue that motivated it in Kakoune. I think right now it could also be useful for basic multi-character pairs.

Overall, I agree that it is a niche command and if you guys don't want to include the command I'd be indifferent to it.

[the-mikedavis]

The use-cases mentioned later in the issue are covered by surround tools. The original use-case I'm not sure I fully understand but it seems like it wouldn't come up often so I bet it could be covered instead by subselecting with a regex of ^.|.$. I've asked on matrix what the commenter's use-case is - I'm leaning towards not adding this unless there's something compelling

[totallyuniquelily]

so I bet it could be covered instead by subselecting with a regex of ^.|.$.

for selections that span across lines, \A.|.\z can be used instead to not match beginning/end of line