Easier boolean attributes

[tabatkins]

From the usage example, it looks like boolean attributes currently have to be manually handled by outputting either their name or an empty string, using a ternary.

This is a bit clumsy. It would be a lot more aesthetically appealing if you could write something like:

const el = html`<video controls?={showControls} url={url}></video>`;

That is, if the attr name is followed by a ?= operator, its value is checked as a boolean, and the attribute is either included or omitted accordingly.

(Any similar sort of syntax would work, of course.)

[straker]

I agree that conditional attributes using a ternary is a bit clumsy. The only concern I have is that doing ?= or a similar syntax would be diverging from what is possible with innerHTML. Now I'm not saying that's a bad thing, it's just that I've been trying to figure out the right balance between how to get this proposal moving forward and getting implementer interest and all the different ways the same problem is being solved.

Since you've been around the block a time or two getting proposals through the spec groups, at what level do you see this API falling under? Should it be something low level that mimics innerHTML like syntax but without the need of an outer element? Or would this be better as a higher level API, which means we should add features that break away from innerHTML but that add more conveniences for the developer?

[tabatkins]

Depends! Both are valid approaches.

In particular, trying to piggyback on whatwg/html#3052 might be useful; the implementors there want to be able to produce "trusted HTML" types, where you know for sure that what you're inserting isn't vulnerable to injection, and having a powerful built-in template to do that with can be useful. You don't want to go too far, but putting in just a few small conveniences might make it more attractive. (Libraries will be able to produce these themselves, so they can handle more complicated/weird templating semantics on their own.)