Function propagateContextChange

code/new-context-api/public/app.js:9589–9663

(workInProgress, context, changedBits, renderExpirationTime)

  }

  function propagateContextChange(workInProgress, context, changedBits, renderExpirationTime) {
    var fiber = workInProgress.child;
    if (fiber !== null) {
      // Set the return pointer of the child to the work-in-progress fiber.
      fiber['return'] = workInProgress;
    }
    while (fiber !== null) {
      var nextFiber = void 0;
      // Visit this fiber.
      switch (fiber.tag) {
        case ContextConsumer:
          // Check if the context matches.
          var observedBits = fiber.stateNode | 0;
          if (fiber.type === context && (observedBits & changedBits) !== 0) {
            // Update the expiration time of all the ancestors, including
            // the alternates.
            var node = fiber;
            while (node !== null) {
              var alternate = node.alternate;
              if (node.expirationTime === NoWork || node.expirationTime > renderExpirationTime) {
                node.expirationTime = renderExpirationTime;
                if (alternate !== null && (alternate.expirationTime === NoWork || alternate.expirationTime > renderExpirationTime)) {
                  alternate.expirationTime = renderExpirationTime;
                }
              } else if (alternate !== null && (alternate.expirationTime === NoWork || alternate.expirationTime > renderExpirationTime)) {
                alternate.expirationTime = renderExpirationTime;
              } else {
                // Neither alternate was updated, which means the rest of the
                // ancestor path already has sufficient priority.
                break;
              }
              node = node['return'];
            }
            // Don't scan deeper than a matching consumer. When we render the
            // consumer, we'll continue scanning from that point. This way the
            // scanning work is time-sliced.
            nextFiber = null;
          } else {
            // Traverse down.
            nextFiber = fiber.child;
          }
          break;
        case ContextProvider:
          // Don't scan deeper if this is a matching provider
          nextFiber = fiber.type === workInProgress.type ? null : fiber.child;
          break;
        default:
          // Traverse down.
          nextFiber = fiber.child;
          break;
      }
      if (nextFiber !== null) {
        // Set the return pointer of the child to the work-in-progress fiber.
        nextFiber['return'] = fiber;
      } else {
        // No child. Traverse to next sibling.
        nextFiber = fiber;
        while (nextFiber !== null) {