docs: clarify performance concerns around props and restProps

[benmccann]

I wonder if there's also something here around whether innerHTML can be used to optimize HTML creation? @dummdidumm may know...

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[dummdidumm]

What do you mean by that?

[benmccann]

I just tested a bit in the REPL

<picture>
    <source srcset={avif} type="image/avif">
    <source srcset={webp} type="image/webp">
    <img src={img.src} width={img.w} height={img.h} alt="Example">
</picture>

gets converted to

picture = element("picture");
picture.innerHTML = `<source srcset="${avif}" type="image/avif"/> <source srcset="${webp}" type="image/webp"/> <img src="${img.src}" width="${img.w}" height="${img.h}" alt="Example"/>`;

while

<picture>
    <source srcset={avif} type="image/avif">
    <source srcset={webp} type="image/webp">
    <img src={img.src} width={img.w} height={img.h} {...$$restProps} alt="Example">
</picture>

gets converted to

			picture = element("picture");
			source0 = element("source");
			t0 = space();
			source1 = element("source");
			t1 = space();
			img_1 = element("img");
			if (!srcset_url_equal(source0, source0_srcset_value = avif)) attr(source0, "srcset", source0_srcset_value);
			attr(source0, "type", "image/avif");
			if (!srcset_url_equal(source1, source1_srcset_value = webp)) attr(source1, "srcset", source1_srcset_value);
			attr(source1, "type", "image/webp");
			set_attributes(img_1, img_data);

I guess that's not really related to the usage of $$restProps specifically though, so probably shouldn't be mentioned here.

[dummdidumm]

Yeah unrelated, also I think we can't optimize this because we don't know if the props which are set are all settable as attributes, some may only be settable through the Dom property.