Declarative shadow roots and Template Instantiation are very different proposals with no overlap.
The only relation here is that with some critical feature done like this and shadow selection, there will be more time to work on Template Instantiation.
I know, as I highlighted, it appears to me that all the hurdles for Template Instantiation have been passed, and its about time we start to see actual movement and traction on this.
its been in the pipeline since 2017 with little major movement on it, while a bunch of things developers didn't actually ask for have managed to have more precedence. Whenever I've pressed for reasons for this, it gets hand waved away that they need solutions for SSR and encapsulation. We have both now.
Honestly should have shipped day one with Web Components, would have made it far more compelling. It has always felt like such a big miss to me by the standards bodies that this didn't get attention.
I was always really bullish on Web Components since the first whispers started...
Then I wanted to start building non-JS websites. And suddenly "Web" Components just weren't an option. Now I've dug even further to SSR, and the shortcoming is painful. I don't want to use Next.js, I want to use HTML. I want standards.
Maybe in 4-5 years this will finally be a solved problem...
> Maybe in 4-5 years this will finally be a solved problem...
Of course it won't. And of course it won't be HTML.
Thing is, Webkit wanted to start with HTML and with all things declarative [1] Google wanted to "move fast".
Result? The need a few dozen more standards to patch deficiencies in WC design, and most of those standards involve piling more and more Javascript on top. See this 2022 status report: https://w3c.github.io/webcomponents-cg/2022.html
So now we are in year 12 of this catastrophe, and you are expecting it to end in another 4-5?
If you want to build non-JS sites, web components won't save you. They require JS. They cannot work without JS.
You're much better off using Next, Nuxt, SvelteKit, SolidStart, Marko... Anything that doesn't use them.
But won't support for declarative shadow DOM solve the web components without JS problem ? I mean, maybe I am wrong, but with this and CSS, it looks as if we can gave custom elements in our HTML without any JS!
There's still no agreed upon "template language" that is markup only in HTML. (That's what the above comments refer to as "Template Instantiation".) So while that template tag looks juicy it still doesn't actually do much of anything without JS. Except for possible the small set of web components where the internal markup is the exact same for every instance of the web component, maybe.
The only relation here is that with some critical feature done like this and shadow selection, there will be more time to work on Template Instantiation.