react-dom-core/lib/ReactFiberBeginWork.js

/**
 * Copyright (c) 2013-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * 
 */

'use strict';

var _require = require('./ReactChildFiber'),
    reconcileChildFibers = _require.reconcileChildFibers,
    reconcileChildFibersInPlace = _require.reconcileChildFibersInPlace,
    cloneChildFibers = _require.cloneChildFibers;

var _require2 = require('./ReactPriorityLevel'),
    LowPriority = _require2.LowPriority;

var ReactTypeOfWork = require('./ReactTypeOfWork');
var IndeterminateComponent = ReactTypeOfWork.IndeterminateComponent,
    FunctionalComponent = ReactTypeOfWork.FunctionalComponent,
    ClassComponent = ReactTypeOfWork.ClassComponent,
    HostContainer = ReactTypeOfWork.HostContainer,
    HostComponent = ReactTypeOfWork.HostComponent,
    CoroutineComponent = ReactTypeOfWork.CoroutineComponent,
    CoroutineHandlerPhase = ReactTypeOfWork.CoroutineHandlerPhase,
    YieldComponent = ReactTypeOfWork.YieldComponent;

var _require3 = require('./ReactPriorityLevel'),
    NoWork = _require3.NoWork,
    OffscreenPriority = _require3.OffscreenPriority;

var _require4 = require('./ReactFiberUpdateQueue'),
    createUpdateQueue = _require4.createUpdateQueue,
    addToQueue = _require4.addToQueue,
    addCallbackToQueue = _require4.addCallbackToQueue,
    mergeUpdateQueue = _require4.mergeUpdateQueue;

var ReactInstanceMap = require('./ReactInstanceMap');

module.exports = function (config, getScheduler) {
  function markChildAsProgressed(current, workInProgress, priorityLevel) {
    // We now have clones. Let's store them as the currently progressed work.
    workInProgress.progressedChild = workInProgress.child;
    workInProgress.progressedPriority = priorityLevel;
    if (current) {
      // We also store it on the current. When the alternate swaps in we can
      // continue from this point.
      current.progressedChild = workInProgress.progressedChild;
      current.progressedPriority = workInProgress.progressedPriority;
    }
  }

  function reconcileChildren(current, workInProgress, nextChildren) {
    var priorityLevel = workInProgress.pendingWorkPriority;
    reconcileChildrenAtPriority(current, workInProgress, nextChildren, priorityLevel);
  }

  function reconcileChildrenAtPriority(current, workInProgress, nextChildren, priorityLevel) {
    // At this point any memoization is no longer valid since we'll have changed
    // the children.
    workInProgress.memoizedProps = null;
    if (current && current.child === workInProgress.child) {
      // If the current child is the same as the work in progress, it means that
      // we haven't yet started any work on these children. Therefore, we use
      // the clone algorithm to create a copy of all the current children.
      workInProgress.child = reconcileChildFibers(workInProgress, workInProgress.child, nextChildren, priorityLevel);
    } else {
      // If, on the other hand, we don't have a current fiber or if it is
      // already using a clone, that means we've already begun some work on this
      // tree and we can continue where we left off by reconciling against the
      // existing children.
      workInProgress.child = reconcileChildFibersInPlace(workInProgress, workInProgress.child, nextChildren, priorityLevel);
    }
    markChildAsProgressed(current, workInProgress, priorityLevel);
  }

  function updateFunctionalComponent(current, workInProgress) {
    var fn = workInProgress.type;
    var props = workInProgress.pendingProps;

    // TODO: Disable this before release, since it is not part of the public API
    // I use this for testing to compare the relative overhead of classes.
    if (typeof fn.shouldComponentUpdate === 'function') {
      if (workInProgress.memoizedProps !== null) {
        if (!fn.shouldComponentUpdate(workInProgress.memoizedProps, props)) {
          return bailoutOnAlreadyFinishedWork(current, workInProgress);
        }
      }
    }

    var nextChildren = fn(props);
    reconcileChildren(current, workInProgress, nextChildren);
    return workInProgress.child;
  }

  function scheduleUpdate(fiber, updateQueue, priorityLevel) {
    var _getScheduler = getScheduler(),
        scheduleDeferredWork = _getScheduler.scheduleDeferredWork;

    fiber.updateQueue = updateQueue;
    // Schedule update on the alternate as well, since we don't know which tree
    // is current.
    if (fiber.alternate) {
      fiber.alternate.updateQueue = updateQueue;
    }
    while (true) {
      if (fiber.pendingWorkPriority === NoWork || fiber.pendingWorkPriority >= priorityLevel) {
        fiber.pendingWorkPriority = priorityLevel;
      }
      if (fiber.alternate) {
        if (fiber.alternate.pendingWorkPriority === NoWork || fiber.alternate.pendingWorkPriority >= priorityLevel) {
          fiber.alternate.pendingWorkPriority = priorityLevel;
        }
      }
      // Duck type root
      if (fiber.stateNode && fiber.stateNode.containerInfo) {
        var root = fiber.stateNode;
        scheduleDeferredWork(root, priorityLevel);
        return;
      }
      if (!fiber['return']) {
        throw new Error('No root!');
      }
      fiber = fiber['return'];
    }
  }

  // Class component state updater
  var updater = {
    enqueueSetState: function (instance, partialState) {
      var fiber = ReactInstanceMap.get(instance);
      var updateQueue = fiber.updateQueue ? addToQueue(fiber.updateQueue, partialState) : createUpdateQueue(partialState);
      scheduleUpdate(fiber, updateQueue, LowPriority);
    },
    enqueueReplaceState: function (instance, state) {
      var fiber = ReactInstanceMap.get(instance);
      var updateQueue = createUpdateQueue(state);
      updateQueue.isReplace = true;
      scheduleUpdate(fiber, updateQueue, LowPriority);
    },
    enqueueForceUpdate: function (instance) {
      var fiber = ReactInstanceMap.get(instance);
      var updateQueue = fiber.updateQueue || createUpdateQueue(null);
      updateQueue.isForced = true;
      scheduleUpdate(fiber, updateQueue, LowPriority);
    },
    enqueueCallback: function (instance, callback) {
      var fiber = ReactInstanceMap.get(instance);
      var updateQueue = fiber.updateQueue ? fiber.updateQueue : createUpdateQueue(null);
      addCallbackToQueue(updateQueue, callback);
      fiber.updateQueue = updateQueue;
      if (fiber.alternate) {
        fiber.alternate.updateQueue = updateQueue;
      }
    }
  };

  function updateClassComponent(current, workInProgress) {
    // A class component update is the result of either new props or new state.
    // Account for the possibly of missing pending props by falling back to the
    // memoized props.
    var props = workInProgress.pendingProps;
    if (!props && current) {
      props = current.memoizedProps;
    }
    // Compute the state using the memoized state and the update queue.
    var updateQueue = workInProgress.updateQueue;
    var previousState = current ? current.memoizedState : null;
    var state = updateQueue ? mergeUpdateQueue(updateQueue, previousState, props) : previousState;

    var instance = workInProgress.stateNode;
    if (!instance) {
      var ctor = workInProgress.type;
      workInProgress.stateNode = instance = new ctor(props);
      state = instance.state || null;
      // The initial state must be added to the update queue in case
      // setState is called before the initial render.
      if (state !== null) {
        workInProgress.updateQueue = createUpdateQueue(state);
      }
      // The instance needs access to the fiber so that it can schedule updates
      ReactInstanceMap.set(instance, workInProgress);
      instance.updater = updater;
    } else if (typeof instance.shouldComponentUpdate === 'function' && !(updateQueue && updateQueue.isForced)) {
      if (workInProgress.memoizedProps !== null) {
        // Reset the props, in case this is a ping-pong case rather than a
        // completed update case. For the completed update case, the instance
        // props will already be the memoizedProps.
        instance.props = workInProgress.memoizedProps;
        instance.state = workInProgress.memoizedState;
        if (!instance.shouldComponentUpdate(props, state)) {
          return bailoutOnAlreadyFinishedWork(current, workInProgress);
        }
      }
    }

    instance.props = props;
    instance.state = state;
    var nextChildren = instance.render();
    reconcileChildren(current, workInProgress, nextChildren);

    return workInProgress.child;
  }

  function updateHostComponent(current, workInProgress) {
    var nextChildren = workInProgress.pendingProps.children;
    if (workInProgress.pendingProps.hidden && workInProgress.pendingWorkPriority !== OffscreenPriority) {
      // If this host component is hidden, we can bail out on the children.
      // We'll rerender the children later at the lower priority.

      // It is unfortunate that we have to do the reconciliation of these
      // children already since that will add them to the tree even though
      // they are not actually done yet. If this is a large set it is also
      // confusing that this takes time to do right now instead of later.

      if (workInProgress.progressedPriority === OffscreenPriority) {
        // If we already made some progress on the offscreen priority before,
        // then we should continue from where we left off.
        workInProgress.child = workInProgress.progressedChild;
      }

      // Reconcile the children and stash them for later work.
      reconcileChildrenAtPriority(current, workInProgress, nextChildren, OffscreenPriority);
      workInProgress.child = current ? current.child : null;
      // Abort and don't process children yet.
      return null;
    } else {
      reconcileChildren(current, workInProgress, nextChildren);
      return workInProgress.child;
    }
  }

  function mountIndeterminateComponent(current, workInProgress) {
    var fn = workInProgress.type;
    var props = workInProgress.pendingProps;
    var value = fn(props);
    if (typeof value === 'object' && value && typeof value.render === 'function') {
      // Proceed under the assumption that this is a class instance
      workInProgress.tag = ClassComponent;
      if (current) {
        current.tag = ClassComponent;
      }
      value = value.render();
    } else {
      // Proceed under the assumption that this is a functional component
      workInProgress.tag = FunctionalComponent;
      if (current) {
        current.tag = FunctionalComponent;
      }
    }
    reconcileChildren(current, workInProgress, value);
    return workInProgress.child;
  }

  function updateCoroutineComponent(current, workInProgress) {
    var coroutine = workInProgress.pendingProps;
    if (!coroutine) {
      throw new Error('Should be resolved by now');
    }
    reconcileChildren(current, workInProgress, coroutine.children);
  }

  /*
  function reuseChildrenEffects(returnFiber : Fiber, firstChild : Fiber) {
    let child = firstChild;
    do {
      // Ensure that the first and last effect of the parent corresponds
      // to the children's first and last effect.
      if (!returnFiber.firstEffect) {
        returnFiber.firstEffect = child.firstEffect;
      }
      if (child.lastEffect) {
        if (returnFiber.lastEffect) {
          returnFiber.lastEffect.nextEffect = child.firstEffect;
        }
        returnFiber.lastEffect = child.lastEffect;
      }
    } while (child = child.sibling);
  }
  */

  function bailoutOnAlreadyFinishedWork(current, workInProgress) {
    var priorityLevel = workInProgress.pendingWorkPriority;

    // TODO: We should ideally be able to bail out early if the children have no
    // more work to do. However, since we don't have a separation of this
    // Fiber's priority and its children yet - we don't know without doing lots
    // of the same work we do anyway. Once we have that separation we can just
    // bail out here if the children has no more work at this priority level.
    // if (workInProgress.priorityOfChildren <= priorityLevel) {
    //   // If there are side-effects in these children that have not yet been
    //   // committed we need to ensure that they get properly transferred up.
    //   if (current && current.child !== workInProgress.child) {
    //     reuseChildrenEffects(workInProgress, child);
    //   }
    //   return null;
    // }

    cloneChildFibers(current, workInProgress);
    markChildAsProgressed(current, workInProgress, priorityLevel);
    return workInProgress.child;
  }

  function bailoutOnLowPriority(current, workInProgress) {
    if (current) {
      workInProgress.child = current.child;
      workInProgress.memoizedProps = current.memoizedProps;
      workInProgress.output = current.output;
    }
    return null;
  }

  function beginWork(current, workInProgress, priorityLevel) {
    if (workInProgress.pendingWorkPriority === NoWork || workInProgress.pendingWorkPriority > priorityLevel) {
      return bailoutOnLowPriority(current, workInProgress);
    }

    if (workInProgress.progressedPriority === priorityLevel) {
      // If we have progressed work on this priority level already, we can
      // proceed this that as the child.
      workInProgress.child = workInProgress.progressedChild;
    }

    if ((workInProgress.pendingProps === null || workInProgress.memoizedProps !== null && workInProgress.pendingProps === workInProgress.memoizedProps) && workInProgress.updateQueue === null) {
      return bailoutOnAlreadyFinishedWork(current, workInProgress);
    }

    switch (workInProgress.tag) {
      case IndeterminateComponent:
        return mountIndeterminateComponent(current, workInProgress);
      case FunctionalComponent:
        return updateFunctionalComponent(current, workInProgress);
      case ClassComponent:
        return updateClassComponent(current, workInProgress);
      case HostContainer:
        reconcileChildren(current, workInProgress, workInProgress.pendingProps);
        // A yield component is just a placeholder, we can just run through the
        // next one immediately.
        if (workInProgress.child) {
          return beginWork(workInProgress.child.alternate, workInProgress.child, priorityLevel);
        }
        return null;
      case HostComponent:
        if (workInProgress.stateNode && typeof config.beginUpdate === 'function') {
          config.beginUpdate(workInProgress.stateNode);
        }
        return updateHostComponent(current, workInProgress);
      case CoroutineHandlerPhase:
        // This is a restart. Reset the tag to the initial phase.
        workInProgress.tag = CoroutineComponent;
      // Intentionally fall through since this is now the same.
      case CoroutineComponent:
        updateCoroutineComponent(current, workInProgress);
        // This doesn't take arbitrary time so we could synchronously just begin
        // eagerly do the work of workInProgress.child as an optimization.
        if (workInProgress.child) {
          return beginWork(workInProgress.child.alternate, workInProgress.child, priorityLevel);
        }
        return workInProgress.child;
      case YieldComponent:
        // A yield component is just a placeholder, we can just run through the
        // next one immediately.
        if (workInProgress.sibling) {
          return beginWork(workInProgress.sibling.alternate, workInProgress.sibling, priorityLevel);
        }
        return null;
      default:
        throw new Error('Unknown unit of work tag');
    }
  }

  return {
    beginWork: beginWork
  };
};