ReactCompositeComponent.js

/**
 * Copyright 2013 Facebook, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * @providesModule ReactCompositeComponent
 */

"use strict";

var ReactComponent = require('ReactComponent');
var ReactContext = require('ReactContext');
var ReactCurrentOwner = require('ReactCurrentOwner');
var ReactErrorUtils = require('ReactErrorUtils');
var ReactOwner = require('ReactOwner');
var ReactPerf = require('ReactPerf');
var ReactPropTransferer = require('ReactPropTransferer');
var ReactPropTypeLocations = require('ReactPropTypeLocations');
var ReactPropTypeLocationNames = require('ReactPropTypeLocationNames');
var ReactUpdates = require('ReactUpdates');

var invariant = require('invariant');
var keyMirror = require('keyMirror');
var merge = require('merge');
var mixInto = require('mixInto');
var objMap = require('objMap');
var shouldUpdateReactComponent = require('shouldUpdateReactComponent');

/**
 * Policies that describe methods in `ReactCompositeComponentInterface`.
 */
var SpecPolicy = keyMirror({
  /**
   * These methods may be defined only once by the class specification or mixin.
   */
  DEFINE_ONCE: null,
  /**
   * These methods may be defined by both the class specification and mixins.
   * Subsequent definitions will be chained. These methods must return void.
   */
  DEFINE_MANY: null,
  /**
   * These methods are overriding the base ReactCompositeComponent class.
   */
  OVERRIDE_BASE: null,
  /**
   * These methods are similar to DEFINE_MANY, except we assume they return
   * objects. We try to merge the keys of the return values of all the mixed in
   * functions. If there is a key conflict we throw.
   */
  DEFINE_MANY_MERGED: null
});

/**
 * Composite components are higher-level components that compose other composite
 * or native components.
 *
 * To create a new type of `ReactCompositeComponent`, pass a specification of
 * your new class to `React.createClass`. The only requirement of your class
 * specification is that you implement a `render` method.
 *
 *   var MyComponent = React.createClass({
 *     render: function() {
 *       return <div>Hello World</div>;
 *     }
 *   });
 *
 * The class specification supports a specific protocol of methods that have
 * special meaning (e.g. `render`). See `ReactCompositeComponentInterface` for
 * more the comprehensive protocol. Any other properties and methods in the
 * class specification will available on the prototype.
 *
 * @interface ReactCompositeComponentInterface
 * @internal
 */
var ReactCompositeComponentInterface = {

  /**
   * An array of Mixin objects to include when defining your component.
   *
   * @type {array}
   * @optional
   */
  mixins: SpecPolicy.DEFINE_MANY,

  /**
   * An object containing properties and methods that should be defined on
   * the component's constructor instead of its prototype (static methods).
   *
   * @type {object}
   * @optional
   */
  statics: SpecPolicy.DEFINE_MANY,

  /**
   * Definition of prop types for this component.
   *
   * @type {object}
   * @optional
   */
  propTypes: SpecPolicy.DEFINE_MANY,

  /**
   * Definition of context types for this component.
   *
   * @type {object}
   * @optional
   */
  contextTypes: SpecPolicy.DEFINE_MANY,

  /**
   * Definition of context types this component sets for its children.
   *
   * @type {object}
   * @optional
   */
  childContextTypes: SpecPolicy.DEFINE_MANY,

  // ==== Definition methods ====

  /**
   * Invoked when the component is mounted. Values in the mapping will be set on
   * `this.props` if that prop is not specified (i.e. using an `in` check).
   *
   * This method is invoked before `getInitialState` and therefore cannot rely
   * on `this.state` or use `this.setState`.
   *
   * @return {object}
   * @optional
   */
  getDefaultProps: SpecPolicy.DEFINE_MANY_MERGED,

  /**
   * Invoked once before the component is mounted. The return value will be used
   * as the initial value of `this.state`.
   *
   *   getInitialState: function() {
   *     return {
   *       isOn: false,
   *       fooBaz: new BazFoo()
   *     }
   *   }
   *
   * @return {object}
   * @optional
   */
  getInitialState: SpecPolicy.DEFINE_MANY_MERGED,

  /**
   * @return {object}
   * @optional
   */
  getChildContext: SpecPolicy.DEFINE_MANY_MERGED,

  /**
   * Uses props from `this.props` and state from `this.state` to render the
   * structure of the component.
   *
   * No guarantees are made about when or how often this method is invoked, so
   * it must not have side effects.
   *
   *   render: function() {
   *     var name = this.props.name;
   *     return <div>Hello, {name}!</div>;
   *   }
   *
   * @return {ReactComponent}
   * @nosideeffects
   * @required
   */
  render: SpecPolicy.DEFINE_ONCE,



  // ==== Delegate methods ====

  /**
   * Invoked when the component is initially created and about to be mounted.
   * This may have side effects, but any external subscriptions or data created
   * by this method must be cleaned up in `componentWillUnmount`.
   *
   * @optional
   */
  componentWillMount: SpecPolicy.DEFINE_MANY,

  /**
   * Invoked when the component has been mounted and has a DOM representation.
   * However, there is no guarantee that the DOM node is in the document.
   *
   * Use this as an opportunity to operate on the DOM when the component has
   * been mounted (initialized and rendered) for the first time.
   *
   * @param {DOMElement} rootNode DOM element representing the component.
   * @optional
   */
  componentDidMount: SpecPolicy.DEFINE_MANY,

  /**
   * Invoked before the component receives new props.
   *
   * Use this as an opportunity to react to a prop transition by updating the
   * state using `this.setState`. Current props are accessed via `this.props`.
   *
   *   componentWillReceiveProps: function(nextProps, nextContext) {
   *     this.setState({
   *       likesIncreasing: nextProps.likeCount > this.props.likeCount
   *     });
   *   }
   *
   * NOTE: There is no equivalent `componentWillReceiveState`. An incoming prop
   * transition may cause a state change, but the opposite is not true. If you
   * need it, you are probably looking for `componentWillUpdate`.
   *
   * @param {object} nextProps
   * @optional
   */
  componentWillReceiveProps: SpecPolicy.DEFINE_MANY,

  /**
   * Invoked while deciding if the component should be updated as a result of
   * receiving new props, state and/or context.
   *
   * Use this as an opportunity to `return false` when you're certain that the
   * transition to the new props/state/context will not require a component
   * update.
   *
   *   shouldComponentUpdate: function(nextProps, nextState, nextContext) {
   *     return !equal(nextProps, this.props) ||
   *       !equal(nextState, this.state) ||
   *       !equal(nextContext, this.context);
   *   }
   *
   * @param {object} nextProps
   * @param {?object} nextState
   * @param {?object} nextContext
   * @return {boolean} True if the component should update.
   * @optional
   */
  shouldComponentUpdate: SpecPolicy.DEFINE_ONCE,

  /**
   * Invoked when the component is about to update due to a transition from
   * `this.props`, `this.state` and `this.context` to `nextProps`, `nextState`
   * and `nextContext`.
   *
   * Use this as an opportunity to perform preparation before an update occurs.
   *
   * NOTE: You **cannot** use `this.setState()` in this method.
   *
   * @param {object} nextProps
   * @param {?object} nextState
   * @param {?object} nextContext
   * @param {ReactReconcileTransaction} transaction
   * @optional
   */
  componentWillUpdate: SpecPolicy.DEFINE_MANY,

  /**
   * Invoked when the component's DOM representation has been updated.
   *
   * Use this as an opportunity to operate on the DOM when the component has
   * been updated.
   *
   * @param {object} prevProps
   * @param {?object} prevState
   * @param {?object} prevContext
   * @param {DOMElement} rootNode DOM element representing the component.
   * @optional
   */
  componentDidUpdate: SpecPolicy.DEFINE_MANY,

  /**
   * Invoked when the component is about to be removed from its parent and have
   * its DOM representation destroyed.
   *
   * Use this as an opportunity to deallocate any external resources.
   *
   * NOTE: There is no `componentDidUnmount` since your component will have been
   * destroyed by that point.
   *
   * @optional
   */
  componentWillUnmount: SpecPolicy.DEFINE_MANY,



  // ==== Advanced methods ====

  /**
   * Updates the component's currently mounted DOM representation.
   *
   * By default, this implements React's rendering and reconciliation algorithm.
   * Sophisticated clients may wish to override this.
   *
   * @param {ReactReconcileTransaction} transaction
   * @internal
   * @overridable
   */
  updateComponent: SpecPolicy.OVERRIDE_BASE

};

/**
 * Mapping from class specification keys to special processing functions.
 *
 * Although these are declared like instance properties in the specification
 * when defining classes using `React.createClass`, they are actually static
 * and are accessible on the constructor instead of the prototype. Despite
 * being static, they must be defined outside of the "statics" key under
 * which all other static methods are defined.
 */
var RESERVED_SPEC_KEYS = {
  displayName: function(ConvenienceConstructor, displayName) {
    ConvenienceConstructor.componentConstructor.displayName = displayName;
  },
  mixins: function(ConvenienceConstructor, mixins) {
    if (mixins) {
      for (var i = 0; i < mixins.length; i++) {
        mixSpecIntoComponent(ConvenienceConstructor, mixins[i]);
      }
    }
  },
  childContextTypes: function(ConvenienceConstructor, childContextTypes) {
    var Constructor = ConvenienceConstructor.componentConstructor;
    validateTypeDef(
      Constructor,
      childContextTypes,
      ReactPropTypeLocations.childContext
    );
    Constructor.childContextTypes = merge(
      Constructor.childContextTypes,
      childContextTypes
    );
  },
  contextTypes: function(ConvenienceConstructor, contextTypes) {
    var Constructor = ConvenienceConstructor.componentConstructor;
    validateTypeDef(
      Constructor,
      contextTypes,
      ReactPropTypeLocations.context
    );
    Constructor.contextTypes = merge(Constructor.contextTypes, contextTypes);
  },
  propTypes: function(ConvenienceConstructor, propTypes) {
    var Constructor = ConvenienceConstructor.componentConstructor;
    validateTypeDef(
      Constructor,
      propTypes,
      ReactPropTypeLocations.prop
    );
    Constructor.propTypes = merge(Constructor.propTypes, propTypes);
  },
  statics: function(ConvenienceConstructor, statics) {
    mixStaticSpecIntoComponent(ConvenienceConstructor, statics);
  }
};

function validateTypeDef(Constructor, typeDef, location) {
  for (var propName in typeDef) {
    if (typeDef.hasOwnProperty(propName)) {
      invariant(
        typeof typeDef[propName] == 'function',
        '%s: %s type `%s` is invalid; it must be a function, usually from ' +
        'React.PropTypes.',
        Constructor.displayName || 'ReactCompositeComponent',
        ReactPropTypeLocationNames[location],
        propName
      );
    }
  }
}

function validateMethodOverride(proto, name) {
  var specPolicy = ReactCompositeComponentInterface[name];

  // Disallow overriding of base class methods unless explicitly allowed.
  if (ReactCompositeComponentMixin.hasOwnProperty(name)) {
    invariant(
      specPolicy === SpecPolicy.OVERRIDE_BASE,
      'ReactCompositeComponentInterface: You are attempting to override ' +
      '`%s` from your class specification. Ensure that your method names ' +
      'do not overlap with React methods.',
      name
    );
  }

  // Disallow defining methods more than once unless explicitly allowed.
  if (proto.hasOwnProperty(name)) {
    invariant(
      specPolicy === SpecPolicy.DEFINE_MANY ||
      specPolicy === SpecPolicy.DEFINE_MANY_MERGED,
      'ReactCompositeComponentInterface: You are attempting to define ' +
      '`%s` on your component more than once. This conflict may be due ' +
      'to a mixin.',
      name
    );
  }
}

function validateLifeCycleOnReplaceState(instance) {
  var compositeLifeCycleState = instance._compositeLifeCycleState;
  invariant(
    instance.isMounted() ||
      compositeLifeCycleState === CompositeLifeCycle.MOUNTING,
    'replaceState(...): Can only update a mounted or mounting component.'
  );
  invariant(compositeLifeCycleState !== CompositeLifeCycle.RECEIVING_STATE,
    'replaceState(...): Cannot update during an existing state transition ' +
    '(such as within `render`). This could potentially cause an infinite ' +
    'loop so it is forbidden.'
  );
  invariant(compositeLifeCycleState !== CompositeLifeCycle.UNMOUNTING,
    'replaceState(...): Cannot update while unmounting component. This ' +
    'usually means you called setState() on an unmounted component.'
  );
}

/**
 * Custom version of `mixInto` which handles policy validation and reserved
 * specification keys when building `ReactCompositeComponent` classses.
 */
function mixSpecIntoComponent(ConvenienceConstructor, spec) {
  var Constructor = ConvenienceConstructor.componentConstructor;
  var proto = Constructor.prototype;
  for (var name in spec) {
    var property = spec[name];
    if (!spec.hasOwnProperty(name) || !property) {
      continue;
    }

    validateMethodOverride(proto, name);

    if (RESERVED_SPEC_KEYS.hasOwnProperty(name)) {
      RESERVED_SPEC_KEYS[name](ConvenienceConstructor, property);
    } else {
      // Setup methods on prototype:
      // The following member methods should not be automatically bound:
      // 1. Expected ReactCompositeComponent methods (in the "interface").
      // 2. Overridden methods (that were mixed in).
      var isCompositeComponentMethod = name in ReactCompositeComponentInterface;
      var isInherited = name in proto;
      var markedDontBind = property.__reactDontBind;
      var isFunction = typeof property === 'function';
      var shouldAutoBind =
        isFunction &&
        !isCompositeComponentMethod &&
        !isInherited &&
        !markedDontBind;

      if (shouldAutoBind) {
        if (!proto.__reactAutoBindMap) {
          proto.__reactAutoBindMap = {};
        }
        proto.__reactAutoBindMap[name] = property;
        proto[name] = property;
      } else {
        if (isInherited) {
          // For methods which are defined more than once, call the existing
          // methods before calling the new property.
          if (ReactCompositeComponentInterface[name] ===
              SpecPolicy.DEFINE_MANY_MERGED) {
            proto[name] = createMergedResultFunction(proto[name], property);
          } else {
            proto[name] = createChainedFunction(proto[name], property);
          }
        } else {
          proto[name] = property;
        }
      }
    }
  }
}

function mixStaticSpecIntoComponent(ConvenienceConstructor, statics) {
  if (!statics) {
    return;
  }
  for (var name in statics) {
    var property = statics[name];
    if (!statics.hasOwnProperty(name) || !property) {
      return;
    }

    var isInherited = name in ConvenienceConstructor;
    var result = property;
    if (isInherited) {
      var existingProperty = ConvenienceConstructor[name];
      var existingType = typeof existingProperty;
      var propertyType = typeof property;
      invariant(
        existingType === 'function' && propertyType === 'function',
        'ReactCompositeComponent: You are attempting to define ' +
        '`%s` on your component more than once, but that is only supported ' +
        'for functions, which are chained together. This conflict may be ' +
        'due to a mixin.',
        name
      );
      result = createChainedFunction(existingProperty, property);
    }
    ConvenienceConstructor[name] = result;
    ConvenienceConstructor.componentConstructor[name] = result;
  }
}

/**
 * Merge two objects, but throw if both contain the same key.
 *
 * @param {object} one The first object, which is mutated.
 * @param {object} two The second object
 * @return {object} one after it has been mutated to contain everything in two.
 */
function mergeObjectsWithNoDuplicateKeys(one, two) {
  invariant(
    one && two && typeof one === 'object' && typeof two === 'object',
    'mergeObjectsWithNoDuplicateKeys(): Cannot merge non-objects'
  );

  objMap(two, function(value, key) {
    invariant(
      one[key] === undefined,
      'mergeObjectsWithNoDuplicateKeys(): ' +
      'Tried to merge two objects with the same key: %s',
      key
    );
    one[key] = value;
  });
  return one;
}

/**
 * Creates a function that invokes two functions and merges their return values.
 *
 * @param {function} one Function to invoke first.
 * @param {function} two Function to invoke second.
 * @return {function} Function that invokes the two argument functions.
 * @private
 */
function createMergedResultFunction(one, two) {
  return function mergedResult() {
    return mergeObjectsWithNoDuplicateKeys(
      one.apply(this, arguments),
      two.apply(this, arguments)
    );
  };
}

/**
 * Creates a function that invokes two functions and ignores their return vales.
 *
 * @param {function} one Function to invoke first.
 * @param {function} two Function to invoke second.
 * @return {function} Function that invokes the two argument functions.
 * @private
 */
function createChainedFunction(one, two) {
  return function chainedFunction() {
    one.apply(this, arguments);
    two.apply(this, arguments);
  };
}

/**
 * `ReactCompositeComponent` maintains an auxiliary life cycle state in
 * `this._compositeLifeCycleState` (which can be null).
 *
 * This is different from the life cycle state maintained by `ReactComponent` in
 * `this._lifeCycleState`. The following diagram shows how the states overlap in
 * time. There are times when the CompositeLifeCycle is null - at those times it
 * is only meaningful to look at ComponentLifeCycle alone.
 *
 * Top Row: ReactComponent.ComponentLifeCycle
 * Low Row: ReactComponent.CompositeLifeCycle
 *
 * +-------+------------------------------------------------------+--------+
 * |  UN   |                    MOUNTED                           |   UN   |
 * |MOUNTED|                                                      | MOUNTED|
 * +-------+------------------------------------------------------+--------+
 * |       ^--------+   +------+   +------+   +------+   +--------^        |
 * |       |        |   |      |   |      |   |      |   |        |        |
 * |    0--|MOUNTING|-0-|RECEIV|-0-|RECEIV|-0-|RECEIV|-0-|   UN   |--->0   |
 * |       |        |   |PROPS |   | PROPS|   | STATE|   |MOUNTING|        |
 * |       |        |   |      |   |      |   |      |   |        |        |
 * |       |        |   |      |   |      |   |      |   |        |        |
 * |       +--------+   +------+   +------+   +------+   +--------+        |
 * |       |                                                      |        |
 * +-------+------------------------------------------------------+--------+
 */
var CompositeLifeCycle = keyMirror({
  /**
   * Components in the process of being mounted respond to state changes
   * differently.
   */
  MOUNTING: null,
  /**
   * Components in the process of being unmounted are guarded against state
   * changes.
   */
  UNMOUNTING: null,
  /**
   * Components that are mounted and receiving new props respond to state
   * changes differently.
   */
  RECEIVING_PROPS: null,
  /**
   * Components that are mounted and receiving new state are guarded against
   * additional state changes.
   */
  RECEIVING_STATE: null
});

/**
 * @lends {ReactCompositeComponent.prototype}
 */
var ReactCompositeComponentMixin = {

  /**
   * Base constructor for all composite component.
   *
   * @param {?object} initialProps
   * @param {*} children
   * @final
   * @internal
   */
  construct: function(initialProps, children) {
    // Children can be either an array or more than one argument
    ReactComponent.Mixin.construct.apply(this, arguments);

    this.state = null;
    this._pendingState = null;

    this.context = this._processContext(ReactContext.current);
    this._currentContext = ReactContext.current;
    this._pendingContext = null;

    this._compositeLifeCycleState = null;
  },

  /**
   * Checks whether or not this composite component is mounted.
   * @return {boolean} True if mounted, false otherwise.
   * @protected
   * @final
   */
  isMounted: function() {
    return ReactComponent.Mixin.isMounted.call(this) &&
      this._compositeLifeCycleState !== CompositeLifeCycle.MOUNTING;
  },

  /**
   * Initializes the component, renders markup, and registers event listeners.
   *
   * @param {string} rootID DOM ID of the root node.
   * @param {ReactReconcileTransaction} transaction
   * @param {number} mountDepth number of components in the owner hierarchy
   * @return {?string} Rendered markup to be inserted into the DOM.
   * @final
   * @internal
   */
  mountComponent: ReactPerf.measure(
    'ReactCompositeComponent',
    'mountComponent',
    function(rootID, transaction, mountDepth) {
      ReactComponent.Mixin.mountComponent.call(
        this,
        rootID,
        transaction,
        mountDepth
      );
      this._compositeLifeCycleState = CompositeLifeCycle.MOUNTING;

      this._defaultProps = this.getDefaultProps ? this.getDefaultProps() : null;
      this._processProps(this.props);

      if (this.__reactAutoBindMap) {
        this._bindAutoBindMethods();
      }

      this.state = this.getInitialState ? this.getInitialState() : null;
      invariant(
        typeof this.state === 'object' && !Array.isArray(this.state),
        '%s.getInitialState(): must return an object or null',
        this.constructor.displayName || 'ReactCompositeComponent'
      );

      this._pendingState = null;
      this._pendingForceUpdate = false;

      if (this.componentWillMount) {
        this.componentWillMount();
        // When mounting, calls to `setState` by `componentWillMount` will set
        // `this._pendingState` without triggering a re-render.
        if (this._pendingState) {
          this.state = this._pendingState;
          this._pendingState = null;
        }
      }

      this._renderedComponent = this._renderValidatedComponent();

      // Done with mounting, `setState` will now trigger UI changes.
      this._compositeLifeCycleState = null;
      var markup = this._renderedComponent.mountComponent(
        rootID,
        transaction,
        mountDepth + 1
      );
      if (this.componentDidMount) {
        transaction.getReactMountReady().enqueue(this, this.componentDidMount);
      }
      return markup;
    }
  ),

  /**
   * Releases any resources allocated by `mountComponent`.
   *
   * @final
   * @internal
   */
  unmountComponent: function() {
    this._compositeLifeCycleState = CompositeLifeCycle.UNMOUNTING;
    if (this.componentWillUnmount) {
      this.componentWillUnmount();
    }
    this._compositeLifeCycleState = null;

    this._defaultProps = null;

    ReactComponent.Mixin.unmountComponent.call(this);
    this._renderedComponent.unmountComponent();
    this._renderedComponent = null;

    if (this.refs) {
      this.refs = null;
    }

    // Some existing components rely on this.props even after they've been
    // destroyed (in event handlers).
    // TODO: this.props = null;
    // TODO: this.state = null;
  },

  /**
   * Sets a subset of the state. Always use this or `replaceState` to mutate
   * state. You should treat `this.state` as immutable.
   *
   * There is no guarantee that `this.state` will be immediately updated, so
   * accessing `this.state` after calling this method may return the old value.
   *
   * There is no guarantee that calls to `setState` will run synchronously,
   * as they may eventually be batched together.  You can provide an optional
   * callback that will be executed when the call to setState is actually
   * completed.
   *
   * @param {object} partialState Next partial state to be merged with state.
   * @param {?function} callback Called after state is updated.
   * @final
   * @protected
   */
  setState: function(partialState, callback) {
    // Merge with `_pendingState` if it exists, otherwise with existing state.
    this.replaceState(
      merge(this._pendingState || this.state, partialState),
      callback
    );
  },

  /**
   * Replaces all of the state. Always use this or `setState` to mutate state.
   * You should treat `this.state` as immutable.
   *
   * There is no guarantee that `this.state` will be immediately updated, so
   * accessing `this.state` after calling this method may return the old value.
   *
   * @param {object} completeState Next state.
   * @param {?function} callback Called after state is updated.
   * @final
   * @protected
   */
  replaceState: function(completeState, callback) {
    validateLifeCycleOnReplaceState(this);
    this._pendingState = completeState;
    ReactUpdates.enqueueUpdate(this, callback);
  },

  /**
   * Filters the context object to only contain keys specified in
   * `contextTypes`, and asserts that they are valid.
   *
   * @param {object} context
   * @return {?object}
   * @private
   */
  _processContext: function(context) {
    var maskedContext = null;
    var contextTypes = this.constructor.contextTypes;
    if (contextTypes) {
      maskedContext = {};
      for (var contextName in contextTypes) {
        maskedContext[contextName] = context[contextName];
      }
      this._checkPropTypes(
        contextTypes,
        maskedContext,
        ReactPropTypeLocations.context
      );
    }
    return maskedContext;
  },

  /**
   * @param {object} currentContext
   * @return {object}
   * @private
   */
  _processChildContext: function(currentContext) {
    var childContext = this.getChildContext && this.getChildContext();
    var displayName = this.constructor.displayName || 'ReactCompositeComponent';
    if (childContext) {
      invariant(
        typeof this.constructor.childContextTypes === 'object',
        '%s.getChildContext(): childContextTypes must be defined in order to ' +
        'use getChildContext().',
        displayName
      );
      this._checkPropTypes(
        this.constructor.childContextTypes,
        childContext,
        ReactPropTypeLocations.childContext
      );
      for (var name in childContext) {
        invariant(
          name in this.constructor.childContextTypes,
          '%s.getChildContext(): key "%s" is not defined in childContextTypes.',
          displayName,
          name
        );
      }
      return merge(currentContext, childContext);
    }
    return currentContext;
  },

  /**
   * Processes props by setting default values for unspecified props and
   * asserting that the props are valid.
   *
   * @param {object} props
   * @private
   */
  _processProps: function(props) {
    var defaultProps = this._defaultProps;
    for (var propName in defaultProps) {
      if (typeof props[propName] === 'undefined') {
        props[propName] = defaultProps[propName];
      }
    }
    var propTypes = this.constructor.propTypes;
    if (propTypes) {
      this._checkPropTypes(propTypes, props, ReactPropTypeLocations.prop);
    }
  },

  /**
   * Assert that the props are valid
   *
   * @param {object} propTypes Map of prop name to a ReactPropType
   * @param {object} props
   * @param {string} location e.g. "prop", "context", "child context"
   * @private
   */
  _checkPropTypes: function(propTypes, props, location) {
    var componentName = this.constructor.displayName;
    for (var propName in propTypes) {
      if (propTypes.hasOwnProperty(propName)) {
        propTypes[propName](props, propName, componentName, location);
      }
    }
  },

  performUpdateIfNecessary: function() {
    var compositeLifeCycleState = this._compositeLifeCycleState;
    // Do not trigger a state transition if we are in the middle of mounting or
    // receiving props because both of those will already be doing this.
    if (compositeLifeCycleState === CompositeLifeCycle.MOUNTING ||
        compositeLifeCycleState === CompositeLifeCycle.RECEIVING_PROPS) {
      return;
    }
    ReactComponent.Mixin.performUpdateIfNecessary.call(this);
  },

  /**
   * If any of `_pendingProps`, `_pendingState`, or `_pendingForceUpdate` is
   * set, update the component.
   *
   * @param {ReactReconcileTransaction} transaction
   * @internal
   */
  _performUpdateIfNecessary: function(transaction) {
    if (this._pendingProps == null &&
        this._pendingState == null &&
        this._pendingContext == null &&
        !this._pendingForceUpdate) {
      return;
    }

    var nextFullContext = this._pendingContext || this._currentContext;
    var nextContext = this._processContext(nextFullContext);
    this._pendingContext = null;

    var nextProps = this.props;
    if (this._pendingProps != null) {
      nextProps = this._pendingProps;
      this._processProps(nextProps);
      this._pendingProps = null;

      this._compositeLifeCycleState = CompositeLifeCycle.RECEIVING_PROPS;
      if (this.componentWillReceiveProps) {
        this.componentWillReceiveProps(nextProps, nextContext);
      }
    }

    this._compositeLifeCycleState = CompositeLifeCycle.RECEIVING_STATE;

    // Unlike props, state, and context, we specifically don't want to set
    // _pendingOwner to null here because it's possible for a component to have
    // a null owner, so we instead make `this._owner === this._pendingOwner`
    // mean that there's no owner change pending.
    var nextOwner = this._pendingOwner;

    var nextState = this._pendingState || this.state;
    this._pendingState = null;

    if (this._pendingForceUpdate ||
        !this.shouldComponentUpdate ||
        this.shouldComponentUpdate(nextProps, nextState, nextContext)) {
      this._pendingForceUpdate = false;
      // Will set `this.props`, `this.state` and `this.context`.
      this._performComponentUpdate(
        nextProps,
        nextOwner,
        nextState,
        nextFullContext,
        nextContext,
        transaction
      );
    } else {
      // If it's determined that a component should not update, we still want
      // to set props and state.
      this.props = nextProps;
      this._owner = nextOwner;
      this.state = nextState;
      this._currentContext = nextFullContext;
      this.context = nextContext;
    }

    this._compositeLifeCycleState = null;
  },

  /**
   * Merges new props and state, notifies delegate methods of update and
   * performs update.
   *
   * @param {object} nextProps Next object to set as properties.
   * @param {?ReactComponent} nextOwner Next component to set as owner
   * @param {?object} nextState Next object to set as state.
   * @param {?object} nextFullContext Next object to set as _currentContext.
   * @param {?object} nextContext Next object to set as context.
   * @param {ReactReconcileTransaction} transaction
   * @private
   */
  _performComponentUpdate: function(
    nextProps,
    nextOwner,
    nextState,
    nextFullContext,
    nextContext,
    transaction
  ) {
    var prevProps = this.props;
    var prevOwner = this._owner;
    var prevState = this.state;
    var prevContext = this.context;

    if (this.componentWillUpdate) {
      this.componentWillUpdate(nextProps, nextState, nextContext);
    }

    this.props = nextProps;
    this._owner = nextOwner;
    this.state = nextState;
    this._currentContext = nextFullContext;
    this.context = nextContext;

    this.updateComponent(
      transaction,
      prevProps,
      prevOwner,
      prevState,
      prevContext
    );

    if (this.componentDidUpdate) {
      transaction.getReactMountReady().enqueue(
        this,
        this.componentDidUpdate.bind(this, prevProps, prevState, prevContext)
      );
    }
  },

  receiveComponent: function(nextComponent, transaction) {
    this._pendingContext = nextComponent._currentContext;
    ReactComponent.Mixin.receiveComponent.call(
      this,
      nextComponent,
      transaction
    );
  },

  /**
   * Updates the component's currently mounted DOM representation.
   *
   * By default, this implements React's rendering and reconciliation algorithm.
   * Sophisticated clients may wish to override this.
   *
   * @param {ReactReconcileTransaction} transaction
   * @param {object} prevProps
   * @param {?ReactComponent} prevOwner
   * @param {?object} prevState
   * @param {?object} prevContext
   * @internal
   * @overridable
   */
  updateComponent: ReactPerf.measure(
    'ReactCompositeComponent',
    'updateComponent',
    function(transaction, prevProps, prevOwner, prevState, prevContext) {
      ReactComponent.Mixin.updateComponent.call(
        this,
        transaction,
        prevProps,
        prevOwner
      );
      var prevComponent = this._renderedComponent;
      var nextComponent = this._renderValidatedComponent();
      if (shouldUpdateReactComponent(prevComponent, nextComponent)) {
        prevComponent.receiveComponent(nextComponent, transaction);
      } else {
        // These two IDs are actually the same! But nothing should rely on that.
        var thisID = this._rootNodeID;
        var prevComponentID = prevComponent._rootNodeID;
        prevComponent.unmountComponent();
        this._renderedComponent = nextComponent;
        var nextMarkup = nextComponent.mountComponent(
          thisID,
          transaction,
          this._mountDepth + 1
        );
        ReactComponent.DOMIDOperations.dangerouslyReplaceNodeWithMarkupByID(
          prevComponentID,
          nextMarkup
        );
      }
    }
  ),

  /**
   * Forces an update. This should only be invoked when it is known with
   * certainty that we are **not** in a DOM transaction.
   *
   * You may want to call this when you know that some deeper aspect of the
   * component's state has changed but `setState` was not called.
   *
   * This will not invoke `shouldUpdateComponent`, but it will invoke
   * `componentWillUpdate` and `componentDidUpdate`.
   *
   * @param {?function} callback Called after update is complete.
   * @final
   * @protected
   */
  forceUpdate: function(callback) {
    var compositeLifeCycleState = this._compositeLifeCycleState;
    invariant(
      this.isMounted() ||
        compositeLifeCycleState === CompositeLifeCycle.MOUNTING,
      'forceUpdate(...): Can only force an update on mounted or mounting ' +
        'components.'
    );
    invariant(
      compositeLifeCycleState !== CompositeLifeCycle.RECEIVING_STATE &&
      compositeLifeCycleState !== CompositeLifeCycle.UNMOUNTING,
      'forceUpdate(...): Cannot force an update while unmounting component ' +
      'or during an existing state transition (such as within `render`).'
    );
    this._pendingForceUpdate = true;
    ReactUpdates.enqueueUpdate(this, callback);
  },

  /**
   * @private
   */
  _renderValidatedComponent: function() {
    var renderedComponent;
    var previousContext = ReactContext.current;
    ReactContext.current = this._processChildContext(this._currentContext);
    ReactCurrentOwner.current = this;
    try {
      renderedComponent = this.render();
    } catch (error) {
      // IE8 requires `catch` in order to use `finally`.
      throw error;
    } finally {
      ReactContext.current = previousContext;
      ReactCurrentOwner.current = null;
    }
    invariant(
      ReactComponent.isValidComponent(renderedComponent),
      '%s.render(): A valid ReactComponent must be returned. You may have ' +
      'returned null, undefined, an array, or some other invalid object.',
      this.constructor.displayName || 'ReactCompositeComponent'
    );
    return renderedComponent;
  },

  /**
   * @private
   */
  _bindAutoBindMethods: function() {
    for (var autoBindKey in this.__reactAutoBindMap) {
      if (!this.__reactAutoBindMap.hasOwnProperty(autoBindKey)) {
        continue;
      }
      var method = this.__reactAutoBindMap[autoBindKey];
      this[autoBindKey] = this._bindAutoBindMethod(ReactErrorUtils.guard(
        method,
        this.constructor.displayName + '.' + autoBindKey
      ));
    }
  },

  /**
   * Binds a method to the component.
   *
   * @param {function} method Method to be bound.
   * @private
   */
  _bindAutoBindMethod: function(method) {
    var component = this;
    var boundMethod = function() {
      return method.apply(component, arguments);
    };
    if (__DEV__) {
      boundMethod.__reactBoundContext = component;
      boundMethod.__reactBoundMethod = method;
      boundMethod.__reactBoundArguments = null;
      var componentName = component.constructor.displayName;
      var _bind = boundMethod.bind;
      boundMethod.bind = function(newThis, ...args) {
        // User is trying to bind() an autobound method; we effectively will
        // ignore the value of "this" that the user is trying to use, so
        // let's warn.
        if (newThis !== component && newThis !== null) {
          console.warn(
            'bind(): React component methods may only be bound to the ' +
            'component instance. See ' + componentName
          );
        } else if (!args.length) {
          console.warn(
            'bind(): You are binding a component method to the component. ' +
            'React does this for you automatically in a high-performance ' +
            'way, so you can safely remove this call. See ' + componentName
          );
          return boundMethod;
        }
        var reboundMethod = _bind.apply(boundMethod, arguments);
        reboundMethod.__reactBoundContext = component;
        reboundMethod.__reactBoundMethod = method;
        reboundMethod.__reactBoundArguments = args;
        return reboundMethod;
      };
    }
    return boundMethod;
  }
};

var ReactCompositeComponentBase = function() {};
mixInto(ReactCompositeComponentBase, ReactComponent.Mixin);
mixInto(ReactCompositeComponentBase, ReactOwner.Mixin);
mixInto(ReactCompositeComponentBase, ReactPropTransferer.Mixin);
mixInto(ReactCompositeComponentBase, ReactCompositeComponentMixin);

/**
 * Module for creating composite components.
 *
 * @class ReactCompositeComponent
 * @extends ReactComponent
 * @extends ReactOwner
 * @extends ReactPropTransferer
 */
var ReactCompositeComponent = {

  LifeCycle: CompositeLifeCycle,

  Base: ReactCompositeComponentBase,

  /**
   * Creates a composite component class given a class specification.
   *
   * @param {object} spec Class specification (which must define `render`).
   * @return {function} Component constructor function.
   * @public
   */
  createClass: function(spec) {
    var Constructor = function() {};
    Constructor.prototype = new ReactCompositeComponentBase();
    Constructor.prototype.constructor = Constructor;

    var ConvenienceConstructor = function(props, children) {
      var instance = new Constructor();
      instance.construct.apply(instance, arguments);
      return instance;
    };
    ConvenienceConstructor.componentConstructor = Constructor;
    ConvenienceConstructor.originalSpec = spec;

    mixSpecIntoComponent(ConvenienceConstructor, spec);

    invariant(
      Constructor.prototype.render,
      'createClass(...): Class specification must implement a `render` method.'
    );

    if (__DEV__) {
      if (Constructor.prototype.componentShouldUpdate) {
        console.warn(
          (spec.displayName || 'A component') + ' has a method called ' +
          'componentShouldUpdate(). Did you mean shouldComponentUpdate()? ' +
          'The name is phrased as a question because the function is ' +
          'expected to return a value.'
         );
      }
    }

    // Reduce time spent doing lookups by setting these on the prototype.
    for (var methodName in ReactCompositeComponentInterface) {
      if (!Constructor.prototype[methodName]) {
        Constructor.prototype[methodName] = null;
      }
    }

    return ConvenienceConstructor;
  },

  /**
   * Checks if a value is a valid component constructor.
   *
   * @param {*}
   * @return {boolean}
   * @public
   */
  isValidClass: function(componentClass) {
    return componentClass instanceof Function &&
           'componentConstructor' in componentClass &&
           componentClass.componentConstructor instanceof Function;
  }
};

module.exports = ReactCompositeComponent;