This fixes the case where a child component is added to the queue before its parent, but should be invalidated by its parent's update. Same logic was present in Vue 2. Properly fixes #910 ref: https://github.com/vuejs/vue-next/issues/910#issuecomment-613097539
@vue/runtime-core
This package is published only for typing and building custom renderers. It is NOT meant to be used in applications.
For full exposed APIs, see src/index.ts. You can also run yarn build runtime-core --types from repo root, which will generate an API report at temp/runtime-core.api.md.
Building a Custom Renderer
import { createRenderer } from '@vue/runtime-core'
const { render, createApp } = createRenderer({
  patchProp,
  insert,
  remove,
  createElement,
  // ...
})
// `render` is the low-level API
// `createApp` returns an app instance with configurable context shared
// by the entire app tree.
export { render, createApp }
export * from '@vue/runtime-core'
See @vue/runtime-dom for how a DOM-targeting renderer is implemented.