Extracted from https://github.com/facebook/react/issues/12643.

We're currently diff a host node in the complete phase even if it has bailed out in the begin phase. By itself, this just means we're doing a little bit more work than necessary. But it also has some observable effects. In particular, https://github.com/facebook/react/issues/13424 (which by itself would be very rare and probably not worth fixing) is made worse because we end up committing update to inputs from another component.

I have a fix for this in https://github.com/facebook/react/pull/13423. Filing this for posterity.
throw new Error(
        'appendChildToContainer() first argument is not a container.',
      );
    }
    appendChildToContainerOrInstance(parentInstance, child);
  }
  function appendChild(
    parentInstance: Instance,
    child: Instance | TextInstance,
  ): void {
    if (typeof (parentInstance: any).rootID === 'string') {
      
      
      throw new Error('appendChild() first argument is not an instance.');
    }
    appendChildToContainerOrInstance(parentInstance, child);
  }
  function insertInContainerOrInstanceBefore(
    parentInstance: Container | Instance,
    child: Instance | TextInstance,
    beforeChild: Instance | TextInstance,
  ): void {
    const index = parentInstance.children.indexOf(child);
    if (index !== -1) {
      parentInstance.children.splice(index, 1);
    }
    const beforeIndex = parentInstance.children.indexOf(beforeChild);
    if (beforeIndex === -1) {
      throw new Error('This child does not exist.');