Function processUpdateQueue

packages/react-reconciler/src/updateQueue.ts:83–158

(
	baseState: State,
	pendingUpdate: Update<State> | null,
	renderLane: Lane,
	onSkipUpdate?: <State>(update: Update<State>) => void
)

}

export const processUpdateQueue = <State>(
	baseState: State,
	pendingUpdate: Update<State> | null,
	renderLane: Lane,
	onSkipUpdate?: <State>(update: Update<State>) => void
): {
	memoizedState: State;
	baseState: State;
	baseQueue: Update<State> | null;
} => {
	const result: ReturnType<typeof processUpdateQueue<State>> = {
		memoizedState: baseState,
		baseState,
		baseQueue: null
	};

	if (pendingUpdate !== null) {
		// 第一个update
		const first = pendingUpdate.next;
		let pending = pendingUpdate.next as Update<any>;

		let newBaseState = baseState;
		let newBaseQueueFirst: Update<State> | null = null;
		let newBaseQueueLast: Update<State> | null = null;
		let newState = baseState;

		do {
			const updateLane = pending.lane;
			if (!isSubsetOfLanes(renderLane, updateLane)) {
				// 优先级不够 被跳过
				const clone = createUpdate(pending.action, pending.lane);

				onSkipUpdate?.(clone);

				// 是不是第一个被跳过的
				if (newBaseQueueFirst === null) {
					// first u0 last = u0
					newBaseQueueFirst = clone;
					newBaseQueueLast = clone;
					newBaseState = newState;
				} else {
					// first u0 -> u1 -> u2
					// last u2
					(newBaseQueueLast as Update<State>).next = clone;
					newBaseQueueLast = clone;
				}
			} else {
				// 优先级足够
				if (newBaseQueueLast !== null) {
					const clone = createUpdate(pending.action, NoLane);
					newBaseQueueLast.next = clone;
					newBaseQueueLast = clone;
				}

				const action = pending.action;
				if (pending.hasEagerState) {
					newState = pending.eagerState;
				} else {