1.6.2: Fix a memory leak in property bindings

[Tao-VanJS]

Hi fellow VanJSers,

Happy halloween! 🎃🎃🎃

I'm happy to announce the release of VanJS 1.6.2. 🎉🎉🎉

1.6.2 is a minor release. It fixes a memory leak caused by a flaw in VanJS’s garbage collection. Consider this example:

const App = () => {
  const visible = van.state(true)
  const value = van.state(0), calls = van.state(0)
  const row = div({
    title: () => {
      ++calls.val
      return value.val
    },
  }, "Row")

  return div(
    p("State: ", value, " · title() calls: ", calls),
    button({onclick: () => visible.val = false}, "Remove row"),
    button({onclick: () => ++value.val}, "Increment"),
    () => visible.val ? row : null,
  )
}

Click Remove row, then Increment. In 1.6.1, the title function still runs, increasing its call count from 1 to 2, even though the row is gone. In 1.6.2, the count stays at 1.

1.6.2 fixes this by tying property computations and debug validators to the lifetime of their own DOM elements. When an element is removed, VanJS stops rerunning its associated callbacks and removes their state subscriptions during cleanup. This allows the callbacks and their captured data to be garbage-collected even if the source states remain in use, fixing both the memory leak and the unnecessary work. The fix applies to both van.js and van.debug.js.

The TypeScript return type of van.hydrate is also corrected from a DOM node to void; its runtime behavior is unchanged.

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With the bug fix, the gzipped bundle now weighs 1078 bytes (1.1kB), up from 1074 bytes (1.0kB) (4 bytes increase); the minified bundle is 2087 bytes (2.0kB), up from 2083 bytes (2.0kB) (4 bytes increase) - still being the smallest reactive UI framework in the world.

❤️ Hope you can enjoy!