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.
const container = rootContainers.get(rootID);
      if (container) {
        return container.children;
      } else {
        return null;
      }
    },
    getOrCreateRootContainer(
      rootID: string = DEFAULT_ROOT_ID,
      isAsync: boolean = false,
    ) {
      let root = roots.get(rootID);