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Comment by pcr910303 | Hacker News Reader

Because that means you’re writing a different dialect of JS. Especially in the Svelte case, where you just need to be aware of what the compiler knows and what they don’t. A leaky abstraction, broken magic IMO.

BTW) I would say that writing a whole compiler to add UI update logic is much ommore over engineering than this solution, or just about any JS reactivity system.

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You don't need to use the syntax sugar, a plain update function attached to the event will do fine, just more verbose. It's in fact _less_ magic when the output JS is perfectly readable, and doesn't require unravelling thousands of lines of runtime libraries.

I'm surprised you'd think of that as a leaky abstraction, but not a `@tracked` decorator. They are both 'different dialects of JS', and both use a compiler.

To be clear, the decorator only involves a compiler because the spec isn’t finished. When it is, it’ll just be normal runtime JS with no need for a compiler. There is a compiler invoked at the template layer, but nothing requires that for the rest of this system to work. Autotracking is a general-purpose reactivity system and it does not require any compilation in a formal sense; Svelt does. None of that is a criticism of Svelte, which I very much like and admire. But the difference is worth understanding clearly!

In terms of the tradeoffs here, I haven’t dug deeply enough into Svelte to have a reasonable opinion beyond the first blush “I really like this!” The way it uses compilation and repurposes unused JS features to build a reactivity DSL is very clever and interesting and the compilation output is smart and well-optimized, even if I find the use of exports to be a bit quirky.

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