Function getEntangledLanes

packages/react-reconciler/src/ReactFiberLane.js:423–471

(root: FiberRoot, renderLanes: Lanes)

}

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

  if ((entangledLanes & InputContinuousLane) !== NoLanes) {
    // When updates are sync by default, we entangle continuous priority updates
    // and default updates, so they render in the same batch. The only reason
    // they use separate lanes is because continuous updates should interrupt
    // transitions, but default updates should not.
    entangledLanes |= entangledLanes & DefaultLane;
  }

  // Check for entangled lanes and add them to the batch.
  //
  // A lane is said to be entangled with another when it's not allowed to render
  // in a batch that does not also include the other lane. Typically we do this
  // when multiple updates have the same source, and we only want to respond to
  // the most recent event from that source.
  //
  // Note that we apply entanglements *after* checking for partial work above.
  // This means that if a lane is entangled during an interleaved event while
  // it's already rendering, we won't interrupt it. This is intentional, since
  // entanglement is usually "best effort": we'll try our best to render the
  // lanes in the same batch, but it's not worth throwing out partially
  // completed work in order to do it.
  // TODO: Reconsider this. The counter-argument is that the partial work
  // represents an intermediate state, which we don't want to show to the user.
  // And by spending extra time finishing it, we're increasing the amount of
  // time it takes to show the final state, which is what they are actually
  // waiting for.
  //
  // For those exceptions where entanglement is semantically important,
  // we should ensure that there is no partial work at the
  // time we apply the entanglement.
  const allEntangledLanes = root.entangledLanes;
  if (allEntangledLanes !== NoLanes) {
    const entanglements = root.entanglements;
    let lanes = entangledLanes & allEntangledLanes;
    while (lanes > 0) {
      const index = pickArbitraryLaneIndex(lanes);
      const lane = 1 << index;

      entangledLanes |= entanglements[index];

      lanes &= ~lane;
    }
  }

  return entangledLanes;
}

function computeExpirationTime(lane: Lane, currentTime: number) {
  switch (lane) {