Function updateHostRoot

lib/assets/react-source/development/react.js:20902–20958

(current, workInProgress, renderExpirationTime)

	}

	function updateHostRoot(current, workInProgress, renderExpirationTime) {
	  pushHostRootContext(workInProgress);
	  var updateQueue = workInProgress.updateQueue;

	  if (!(current !== null && updateQueue !== null)) {
	    {
	      throw Error( "If the root does not have an updateQueue, we should have already bailed out. This error is likely caused by a bug in React. Please file an issue." );
	    }
	  }

	  var nextProps = workInProgress.pendingProps;
	  var prevState = workInProgress.memoizedState;
	  var prevChildren = prevState !== null ? prevState.element : null;
	  cloneUpdateQueue(current, workInProgress);
	  processUpdateQueue(workInProgress, nextProps, null, renderExpirationTime);
	  var nextState = workInProgress.memoizedState; // Caution: React DevTools currently depends on this property
	  // being called "element".

	  var nextChildren = nextState.element;

	  if (nextChildren === prevChildren) {
	    // If the state is the same as before, that's a bailout because we had
	    // no work that expires at this time.
	    resetHydrationState();
	    return bailoutOnAlreadyFinishedWork(current, workInProgress, renderExpirationTime);
	  }

	  var root = workInProgress.stateNode;

	  if (root.hydrate && enterHydrationState(workInProgress)) {
	    // If we don't have any current children this might be the first pass.
	    // We always try to hydrate. If this isn't a hydration pass there won't
	    // be any children to hydrate which is effectively the same thing as
	    // not hydrating.
	    var child = mountChildFibers(workInProgress, null, nextChildren, renderExpirationTime);
	    workInProgress.child = child;
	    var node = child;

	    while (node) {
	      // Mark each child as hydrating. This is a fast path to know whether this
	      // tree is part of a hydrating tree. This is used to determine if a child
	      // node has fully mounted yet, and for scheduling event replaying.
	      // Conceptually this is similar to Placement in that a new subtree is
	      // inserted into the React tree here. It just happens to not need DOM
	      // mutations because it already exists.
	      node.effectTag = node.effectTag & ~Placement | Hydrating;
	      node = node.sibling;
	    }
	  } else {
	    // Otherwise reset hydration state in case we aborted and resumed another
	    // root.
	    reconcileChildren(current, workInProgress, nextChildren, renderExpirationTime);
	    resetHydrationState();
	  }

	  return workInProgress.child;
	}