Function refreshComputed

packages/reactivity/src/effect.ts:376–430

(computed: ComputedRefImpl)

 * @internal
 */
export function refreshComputed(computed: ComputedRefImpl): undefined {
  if (
    computed.flags & EffectFlags.TRACKING &&
    !(computed.flags & EffectFlags.DIRTY)
  ) {
    return
  }
  computed.flags &= ~EffectFlags.DIRTY

  // Global version fast path when no reactive changes has happened since
  // last refresh.
  if (computed.globalVersion === globalVersion) {
    return
  }
  computed.globalVersion = globalVersion

  // In SSR there will be no render effect, so the computed has no subscriber
  // and therefore tracks no deps, thus we cannot rely on the dirty check.
  // Instead, computed always re-evaluate and relies on the globalVersion
  // fast path above for caching.
  // #12337 if computed has no deps (does not rely on any reactive data) and evaluated,
  // there is no need to re-evaluate.
  if (
    !computed.isSSR &&
    computed.flags & EffectFlags.EVALUATED &&
    ((!computed.deps && !(computed as any)._dirty) || !isDirty(computed))
  ) {
    return
  }
  computed.flags |= EffectFlags.RUNNING

  const dep = computed.dep
  const prevSub = activeSub
  const prevShouldTrack = shouldTrack
  activeSub = computed
  shouldTrack = true

  try {
    prepareDeps(computed)
    const value = computed.fn(computed._value)
    if (dep.version === 0 || hasChanged(value, computed._value)) {
      computed.flags |= EffectFlags.EVALUATED
      computed._value = value
      dep.version++
    }
  } catch (err) {
    dep.version++
    throw err
  } finally {
    activeSub = prevSub
    shouldTrack = prevShouldTrack
    cleanupDeps(computed)
    computed.flags &= ~EffectFlags.RUNNING
  }
}

function removeSub(link: Link, soft = false) {
  const { dep, prevSub, nextSub } = link