react-dom-core/lib/ReactFiber.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 ReactTypeOfWork = require('./ReactTypeOfWork');
var IndeterminateComponent = ReactTypeOfWork.IndeterminateComponent,
    ClassComponent = ReactTypeOfWork.ClassComponent,
    HostContainer = ReactTypeOfWork.HostContainer,
    HostComponent = ReactTypeOfWork.HostComponent,
    CoroutineComponent = ReactTypeOfWork.CoroutineComponent,
    YieldComponent = ReactTypeOfWork.YieldComponent;

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

// An Instance is shared between all versions of a component. We can easily
// break this out into a separate object to avoid copying so much to the
// alternate versions of the tree. We put this on a single object for now to
// minimize the number of objects created during the initial render.


// A Fiber is work on a Component that needs to be done or was done. There can
// be more than one per component.


// This is a constructor of a POJO instead of a constructor function for a few
// reasons:
// 1) Nobody should add any instance methods on this. Instance methods can be
//    more difficult to predict when they get optimized and they are almost
//    never inlined properly in static compilers.
// 2) Nobody should rely on `instanceof Fiber` for type testing. We should
//    always know when it is a fiber.
// 3) We can easily go from a createFiber call to calling a constructor if that
//    is faster. The opposite is not true.
// 4) We might want to experiment with using numeric keys since they are easier
//    to optimize in a non-JIT environment.
// 5) It should be easy to port this to a C struct and keep a C implementation
//    compatible.
var createFiber = function (tag, key) {
  return {
    // Instance

    tag: tag,

    key: key,

    type: null,

    stateNode: null,

    // Fiber

    'return': null,

    child: null,
    sibling: null,

    ref: null,

    pendingProps: null,
    memoizedProps: null,
    updateQueue: null,
    memoizedState: null,
    callbackList: null,
    output: null,

    nextEffect: null,
    firstEffect: null,
    lastEffect: null,

    pendingWorkPriority: NoWork,
    progressedPriority: NoWork,
    progressedChild: null,

    alternate: null
  };
};

function shouldConstruct(Component) {
  return !!(Component.prototype && Component.prototype.isReactComponent);
}

// This is used to create an alternate fiber to do work on.
// TODO: Rename to createWorkInProgressFiber or something like that.
exports.cloneFiber = function (fiber, priorityLevel) {
  // We clone to get a work in progress. That means that this fiber is the
  // current. To make it safe to reuse that fiber later on as work in progress
  // we need to reset its work in progress flag now. We don't have an
  // opportunity to do this earlier since we don't traverse the tree when
  // the work in progress tree becomes the current tree.
  // fiber.progressedPriority = NoWork;
  // fiber.progressedChild = null;

  // We use a double buffering pooling technique because we know that we'll only
  // ever need at most two versions of a tree. We pool the "other" unused node
  // that we're free to reuse. This is lazily created to avoid allocating extra
  // objects for things that are never updated. It also allow us to reclaim the
  // extra memory if needed.
  var alt = fiber.alternate;
  if (alt) {
    // Whenever we clone, we do so to get a new work in progress.
    // This ensures that we've reset these in the new tree.
    alt.nextEffect = null;
    alt.firstEffect = null;
    alt.lastEffect = null;
  } else {
    // This should not have an alternate already
    alt = createFiber(fiber.tag, fiber.key);
    alt.type = fiber.type;

    alt.progressedChild = fiber.progressedChild;
    alt.progressedPriority = fiber.progressedPriority;

    alt.alternate = fiber;
    fiber.alternate = alt;
  }

  alt.stateNode = fiber.stateNode;
  alt.child = fiber.child;
  alt.sibling = fiber.sibling; // This should always be overridden. TODO: null
  alt.ref = fiber.ref;
  // pendingProps is here for symmetry but is unnecessary in practice for now.
  // TODO: Pass in the new pendingProps as an argument maybe?
  alt.pendingProps = fiber.pendingProps;
  alt.updateQueue = fiber.updateQueue;
  alt.callbackList = fiber.callbackList;
  alt.pendingWorkPriority = priorityLevel;

  alt.memoizedProps = fiber.memoizedProps;
  alt.output = fiber.output;

  return alt;
};

exports.createHostContainerFiber = function () {
  var fiber = createFiber(HostContainer, null);
  return fiber;
};

exports.createFiberFromElement = function (element, priorityLevel) {
  // $FlowFixMe: ReactElement.key is currently defined as ?string but should be defined as null | string in Flow.
  var fiber = createFiberFromElementType(element.type, element.key);
  fiber.pendingProps = element.props;
  fiber.pendingWorkPriority = priorityLevel;
  return fiber;
};

function createFiberFromElementType(type, key) {
  var fiber = void 0;
  if (typeof type === 'function') {
    fiber = shouldConstruct(type) ? createFiber(ClassComponent, key) : createFiber(IndeterminateComponent, key);
    fiber.type = type;
  } else if (typeof type === 'string') {
    fiber = createFiber(HostComponent, key);
    fiber.type = type;
  } else if (typeof type === 'object' && type !== null) {
    // Currently assumed to be a continuation and therefore is a fiber already.
    fiber = type;
  } else {
    throw new Error('Unknown component type: ' + typeof type);
  }
  return fiber;
}

exports.createFiberFromElementType = createFiberFromElementType;

exports.createFiberFromCoroutine = function (coroutine, priorityLevel) {
  var fiber = createFiber(CoroutineComponent, coroutine.key);
  fiber.type = coroutine.handler;
  fiber.pendingProps = coroutine;
  fiber.pendingWorkPriority = priorityLevel;
  return fiber;
};

exports.createFiberFromYield = function (yieldNode, priorityLevel) {
  var fiber = createFiber(YieldComponent, yieldNode.key);
  fiber.pendingProps = {};
  return fiber;
};