Function checkIfRootIsPrerendering

packages/react-reconciler/src/ReactFiberLane.js:408–421

(
  root: FiberRoot,
  renderLanes: Lanes,
)

}

export function checkIfRootIsPrerendering(
  root: FiberRoot,
  renderLanes: Lanes,
): boolean {
  const pendingLanes = root.pendingLanes;
  const suspendedLanes = root.suspendedLanes;
  const pingedLanes = root.pingedLanes;
  // Remove lanes that are suspended (but not pinged)
  const unblockedLanes = pendingLanes & ~(suspendedLanes & ~pingedLanes);

  // If there are no unsuspended or pinged lanes, that implies that we're
  // performing a prerender.
  return (unblockedLanes & renderLanes) === 0;
}

export function getEntangledLanes(root: FiberRoot, renderLanes: Lanes): Lanes {
  let entangledLanes = renderLanes;