[wentin]

In Svelte 4, the let counter = 0 syntax is already reactive by default, a feature enabled by the compiler. This has been the status quo for Svelte prior to the rune change. The introduction of the $state(0) rune actually provides more hints about its reactivity than before, and restore the original meaning of let counter = 0 (in rune mode). While it's true that the compiler's "invasion" into JS/TS syntax has been a point of discussion, this invasion has been happening for a while, and the initial shock wave has been well-absorbed by the community.

Interestingly, the new changes could be seen as a retreat from that initial invasion, likely triggering a different response from the community. In fact, the resistance I've seen (and my own as well) has been in the opposite direction—it's hating this retreat, complaining Svelte becoming less "magical." and more close to regular joe Javascript.

[EvanYou]

I’m specifically taking about non-component context, i.e. plain JS/TS files.

Previously Svelte was able to get a pass on this because magic only happens in svelte files - but in the future, any JS/TS files in a rune-enabled Svelte project will technically be SvelteScript, this never happened before and I doubt the community has already “absorbed” how significant this change is.

[rsimp]

This is a really great point. I think something like a `.svelte.js` file extension is warranted here. This would key tooling to when it needs to interpret runes, and makes it clear which files in a codebase require the svelte compiler. These files clearly aren't just js/ts at this point, but I think its fine as long as they're marked as such. Custom react hooks, for instance, aren't usable outside of the runtime but can be transpiled without issues by esbuild/tsc and interpreted correctly by a js/ts language server.

As long as it's marked separately from js/ts I don't think its a huge issue though. Svelte files already have script tags that aren't completely vanilla js/ts.