SSE swap with `transition:true` doesn't trigger view transitions

[cszczepaniak]

It seems like the view transitions API of HTMX doesn't play nicely with the SSE extension (maybe related to #65?)

With the following HTML, the elements do not have an animated transition when updated via SSE (just shuffling the order of them), but when the order is shuffled via the GET request from the button they do transition as expected (with an animation).

<ul
	id="items"
	hx-swap="transition:true"
	hx-ext="sse"
	sse-connect="/sse"
	sse-swap="values"
>
	<li id="item0" style="view-transition-name:item_a;">a</li>
	<li id="item1" style="view-transition-name:item_b;">b</li>
	<li id="item2" style="view-transition-name:item_c;">c</li>
	<li id="item3" style="view-transition-name:item_d;">e</li>
</ul>
<button hx-get="/list" hx-target="#items" hx-swap="transition:true">Click</button>

[cszczepaniak]

I suppose this is because transitions seem to happen within handleAjaxResponse in HTMX: https://github.com/bigskysoftware/htmx/blob/master/src/htmx.js#L4883-L4892

...whereas the SSE extension only calls swap directly: https://github.com/bigskysoftware/htmx-extensions/blob/main/src/sse/sse.js#L283

What do we think about the SSE doing a similar wrapping if transition:true is specified?

[RobMaskell]

@cszczepaniak Could it be the same issue as #127 for which there is an HTMX main project PR bigskysoftware/htmx#2845 waiting for review?

[cszczepaniak]

@RobMaskell it's a very similar issue, but that PR doesn't have the view transition but of the swap. Once that PR is merged though, I imagine we'd take the same approach to fix this.

[RobMaskell]

@cszczepaniak doesn't seem like that PR is very high up the priority list, I was sort of hoping it might fix this too so it might give it a little push

[cszczepaniak]

@RobMaskell sure, if you want to pull the view transition handling into your PR, that would work as well. It shouldn't be too much more work!

[RobMaskell]

@cszczepaniak slight misunderstanding, I did raise the ticket for the SSE / API / swapdelay issue but it had already been fixed by someone else in that PR. It just hasn't made it to the top of the merge queue yet I guess

[cszczepaniak]

@RobMaskell ah right I see that now, sorry! Hopefully that there is an additional issue will push it up the queue.

[MichaelWest22]

Just put up a possible PR that can hopefully fix this gap