Unclear areas of computed caching

[Nokic233]

case 1:

<script setup>
import { reactive, computed } from 'vue'

const state = reactive({ count: 1 })

const double = computed(() => {
  console.log('c');
  return 2
})

console.log(double.value)
console.log(double.value)

// output:
// c
// 2
// 2

</script>

case 2:

<script setup>
import { reactive, computed } from 'vue'

const state = reactive({ count: 1 })

const double = computed(() => {
  console.log('c');
  return 2
})

console.log(double.value)
state.count++ // add code
console.log(double.value)

// expect output
// c
// 2
// 2

// actual output
// c
// 2
// c
// 2

</script>

case 2 link: https://play.vuejs.org/#eNp9UctOwzAQ/BXLl6Rq5aoULqWtBKgHOAACjpZQSLYhxbEtP0KlKP/O2lHaHlBu3t2Z8cxuS++0Zo0HuqJrm5tKO2LBeb3lsqq1Mo60xECWu6qBGclVrb2DgnRkb1RNEmQmXHKZK2mR6TIHZHMipC0yvHQrsiDd5IwrlP8SATjopemEbLak5ZJgT1olgAlVpkmeTG5D06AnI8kVl71OrzTAej3WZMIDjqMNFn+eTpE+AuVyPe9jY2AsHNRaIBur9fyioDPqLOrsq5IdrJK4rmiW0xChEmBetKvwH05XfYwwy4RQv0+x54yH2dDPvyH/+ad/sMfQ4/TVgAXTAKenmctMCa4f796f4Yjv07BWhReIHhm+Ae7AB4897N7LAm1f4KLbx3j0SpYfdnd0IO0QKhgNyC7iOcXLP4xEP9tdsuvIw9PhFj8bMEETF7hkN2yxpN0fIHPZSQ==

Why does changing a state variable that is not used in computing properties cause the cache of computing properties to become invalid?

[skirtles-code]

I believe it's the bug described at #12337. It's a regression that occurred in 3.5.6 (it works as you're expecting in 3.5.5). It also only affects a computed with no dependencies, which is rare in practice.