factoryWithTypeCheckers.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 ReactIs = require('react-is');
var assign = require('object-assign');

var ReactPropTypesSecret = require('./lib/ReactPropTypesSecret');
var has = require('./lib/has');
var forEach = require('./lib/forEach');
var checkPropTypes = require('./checkPropTypes');

var printWarning = function() {};

if (process.env.NODE_ENV !== 'production') {
  printWarning = function(text) {
    var message = 'Warning: ' + text;
    if (typeof console !== 'undefined') {
      console.error(message);
    }
    try {
      // --- Welcome to debugging React ---
      // This error was thrown as a convenience so that you can use this stack
      // to find the callsite that caused this warning to fire.
      throw new Error(message);
    } catch (x) {}
  };
}

function emptyFunctionThatReturnsNull() {
  return null;
}

function isSet(maybeSet) {
  try {
    Object.getOwnPropertyDescriptor(Set.prototype, 'size').get.call(maybeSet);
    return true
  } catch(e) { return false; }
}

function isMap(maybeMap) {
  try {
    Object.getOwnPropertyDescriptor(Map.prototype, 'size').get.call(maybeMap);
    return true
  } catch(e) { return false; }
}

module.exports = function(isValidElement, throwOnDirectAccess) {
  /* global Symbol */
  var ITERATOR_SYMBOL = typeof Symbol === 'function' && Symbol.iterator;
  var FAUX_ITERATOR_SYMBOL = '@@iterator'; // Before Symbol spec.

  /**
   * Returns the iterator method function contained on the iterable object.
   *
   * Be sure to invoke the function with the iterable as context:
   *
   *     var iteratorFn = getIteratorFn(myIterable);
   *     if (iteratorFn) {
   *       var iterator = iteratorFn.call(myIterable);
   *       ...
   *     }
   *
   * @param {?object} maybeIterable
   * @return {?function}
   */
  function getIteratorFn(maybeIterable) {
    var iteratorFn = maybeIterable && (ITERATOR_SYMBOL && maybeIterable[ITERATOR_SYMBOL] || maybeIterable[FAUX_ITERATOR_SYMBOL]);
    if (typeof iteratorFn === 'function') {
      return iteratorFn;
    }
  }

  /**
   * Collection of methods that allow declaration and validation of props that are
   * supplied to React components. Example usage:
   *
   *   var Props = require('ReactPropTypes');
   *   var MyArticle = React.createClass({
   *     propTypes: {
   *       // An optional string prop named "description".
   *       description: Props.string,
   *
   *       // A required enum prop named "category".
   *       category: Props.oneOf(['News','Photos']).isRequired,
   *
   *       // A prop named "dialog" that requires an instance of Dialog.
   *       dialog: Props.instanceOf(Dialog).isRequired
   *     },
   *     render: function() { ... }
   *   });
   *
   * A more formal specification of how these methods are used:
   *
   *   type := array|bool|func|object|number|string|oneOf([...])|instanceOf(...)
   *   decl := ReactPropTypes.{type}(.isRequired)?
   *
   * Each and every declaration produces a function with the same signature. This
   * allows the creation of custom validation functions. For example:
   *
   *  var MyLink = React.createClass({
   *    propTypes: {
   *      // An optional string or URI prop named "href".
   *      href: function(props, propName, componentName) {
   *        var propValue = props[propName];
   *        if (propValue != null && typeof propValue !== 'string' &&
   *            !(propValue instanceof URI)) {
   *          return new Error(
   *            'Expected a string or an URI for ' + propName + ' in ' +
   *            componentName
   *          );
   *        }
   *      }
   *    },
   *    render: function() {...}
   *  });
   *
   * @internal
   */

  var ANONYMOUS = '<<anonymous>>';

  // Important!
  // Keep this list in sync with production version in `./factoryWithThrowingShims.js`.
  var ReactPropTypes = {
    array: createPrimitiveTypeChecker('array'),
    bool: createPrimitiveTypeChecker('boolean'),
    func: createPrimitiveTypeChecker('function'),
    number: createPrimitiveTypeChecker('number'),
    object: createPrimitiveTypeChecker('object'),
    string: createPrimitiveTypeChecker('string'),
    symbol: createPrimitiveTypeChecker('symbol'),

    any: createAnyTypeChecker(),
    arrayOf: createArrayOfTypeChecker,
    tupleOf: createTupleOfTypeChecker,
    iterableOf: createIterableOfTypeChecker,
    mapOf: createMapOfTypeChecker,
    setOf: createSetOfTypeChecker,
    element: createElementTypeChecker(),
    elementType: createElementTypeTypeChecker(),
    instanceOf: createInstanceTypeChecker,
    node: createNodeChecker(),
    objectOf: createObjectOfTypeChecker,
    oneOf: createEnumTypeChecker,
    oneOfType: createUnionTypeChecker,
    shape: createShapeTypeChecker,
    exact: createStrictShapeTypeChecker,
  };

  /**
   * inlined Object.is polyfill to avoid requiring consumers ship their own
   * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is
   */
  /*eslint-disable no-self-compare*/
  function is(x, y) {
    // SameValue algorithm
    if (x === y) {
      // Steps 1-5, 7-10
      // Steps 6.b-6.e: +0 != -0
      return x !== 0 || 1 / x === 1 / y;
    } else {
      // Step 6.a: NaN == NaN
      return x !== x && y !== y;
    }
  }
  /*eslint-enable no-self-compare*/

  /**
   * We use an Error-like object for backward compatibility as people may call
   * PropTypes directly and inspect their output. However, we don't use real
   * Errors anymore. We don't inspect their stack anyway, and creating them
   * is prohibitively expensive if they are created too often, such as what
   * happens in oneOfType() for any type before the one that matched.
   */
  function PropTypeError(message, data) {
    this.message = message;
    this.data = data && typeof data === 'object' ? data: {};
    this.stack = '';
  }
  // Make `instanceof Error` still work for returned errors.
  PropTypeError.prototype = Error.prototype;

  function createChainableTypeChecker(validate) {
    if (process.env.NODE_ENV !== 'production') {
      var manualPropTypeCallCache = {};
      var manualPropTypeWarningCount = 0;
    }
    function checkType(isRequired, props, propName, componentName, location, propFullName, secret) {
      componentName = componentName || ANONYMOUS;
      propFullName = propFullName || propName;

      if (secret !== ReactPropTypesSecret) {
        if (throwOnDirectAccess) {
          // New behavior only for users of `prop-types` package
          var err = new Error(
            'Calling PropTypes validators directly is not supported by the `prop-types` package. ' +
            'Use `PropTypes.checkPropTypes()` to call them. ' +
            'Read more at http://fb.me/use-check-prop-types'
          );
          err.name = 'Invariant Violation';
          throw err;
        } else if (process.env.NODE_ENV !== 'production' && typeof console !== 'undefined') {
          // Old behavior for people using React.PropTypes
          var cacheKey = componentName + ':' + propName;
          if (
            !manualPropTypeCallCache[cacheKey] &&
            // Avoid spamming the console because they are often not actionable except for lib authors
            manualPropTypeWarningCount < 3
          ) {
            printWarning(
              'You are manually calling a React.PropTypes validation ' +
              'function for the `' + propFullName + '` prop on `' + componentName  + '`. This is deprecated ' +
              'and will throw in the standalone `prop-types` package. ' +
              'You may be seeing this warning due to a third-party PropTypes ' +
              'library. See https://fb.me/react-warning-dont-call-proptypes ' + 'for details.'
            );
            manualPropTypeCallCache[cacheKey] = true;
            manualPropTypeWarningCount++;
          }
        }
      }
      if (props[propName] == null) {
        if (isRequired) {
          if (props[propName] === null) {
            return new PropTypeError('The ' + location + ' `' + propFullName + '` is marked as required ' + ('in `' + componentName + '`, but its value is `null`.'));
          }
          return new PropTypeError('The ' + location + ' `' + propFullName + '` is marked as required in ' + ('`' + componentName + '`, but its value is `undefined`.'));
        }
        return null;
      } else {
        return validate(props, propName, componentName, location, propFullName);
      }
    }

    var chainedCheckType = checkType.bind(null, false);
    chainedCheckType.isRequired = checkType.bind(null, true);

    return chainedCheckType;
  }

  function createPrimitiveTypeChecker(expectedType) {
    function validate(props, propName, componentName, location, propFullName, secret) {
      var propValue = props[propName];
      var propType = getPropType(propValue);
      if (propType !== expectedType) {
        // `propValue` being instance of, say, date/regexp, pass the 'object'
        // check, but we can offer a more precise error message here rather than
        // 'of type `object`'.
        var preciseType = getPreciseType(propValue);

        return new PropTypeError(
          'Invalid ' + location + ' `' + propFullName + '` of type ' + ('`' + preciseType + '` supplied to `' + componentName + '`, expected ') + ('`' + expectedType + '`.'),
          {expectedType: expectedType}
        );
      }
      return null;
    }
    return createChainableTypeChecker(validate);
  }

  function createAnyTypeChecker() {
    return createChainableTypeChecker(emptyFunctionThatReturnsNull);
  }

  function createArrayOfTypeChecker(typeChecker) {
    function validate(props, propName, componentName, location, propFullName) {
      if (typeof typeChecker !== 'function') {
        return new PropTypeError('Property `' + propFullName + '` of component `' + componentName + '` has invalid PropType notation inside arrayOf.');
      }
      var propValue = props[propName];
      if (!Array.isArray(propValue)) {
        var propType = getPropType(propValue);
        return new PropTypeError('Invalid ' + location + ' `' + propFullName + '` of type ' + ('`' + propType + '` supplied to `' + componentName + '`, expected an array.'));
      }
      for (var i = 0; i < propValue.length; i++) {
        var error = typeChecker(propValue, i, componentName, location, propFullName + '[' + i + ']', ReactPropTypesSecret);
        if (error instanceof Error) {
          return error;
        }
      }
      return null;
    }
    return createChainableTypeChecker(validate);
  }
  
  function createTupleOfTypeChecker(typeCheckerTuple) {
    var argsInvalid = !Array.isArray(typeCheckerTuple) || !typeCheckerTuple.every(function (checker) { return typeof checker === 'function'});

    function validate(props, propName, componentName, location, propFullName) {
      if (argsInvalid) {
        return new PropTypeError('Property `' + propFullName + '` of component `' + componentName + '` has invalid PropType notation inside tupleOf.')
      }
      var propValue = props[propName];
      if (!Array.isArray(propValue)) {
        var propType = getPropType(propValue);
        return new PropTypeError('Invalid ' + location + ' `' + propFullName + '` of type ' + '`' + propType + '` supplied to `' + componentName + '`, expected an array.');
      }
      if (propValue.length !== typeCheckerTuple.length) {
        return new PropTypeError('Invalid ' + location + ' `' + propFullName + '` of length ' + '`' + propValue.length + '` supplied to `' + componentName + '`, expected an array of length `' + typeCheckerTuple.length + '`.');
      }
      for (var i = 0; i < typeCheckerTuple.length; i++) {
        var typeChecker = typeCheckerTuple[i];
        var error = typeChecker(propValue, i, componentName, location, propFullName + '[' + i + ']', ReactPropTypesSecret);
        if (error instanceof Error) {
          return error;
        }
      }
      return null;
    }
    return createChainableTypeChecker(validate);
  }

  function createIterableOfTypeChecker(typeChecker) {
    function validate(props, propName, componentName, location, propFullName) {
      if (typeof typeChecker !== 'function') {
        return new PropTypeError('Property `' + propFullName + '` of component `' + componentName + '` has invalid PropType notation inside iterableOf.');
      }
      if (!(Symbol && Symbol.iterator)) {
        return new PropTypeError('Cannot use `PropTypes.iterableOf` if Symbol.iterator is not present');
      }
      var error;
      var propValue = props[propName];

      if (typeof propValue[Symbol.iterator] !== 'function') {
        var propType = getPropType(propValue);
        return new PropTypeError('Invalid ' + location + ' `' + propFullName + '` of type ' + '`' + propType + '` supplied to `' + componentName + '`, expected an iterable.');
      }

      forEach(propValue, function (value) {
        var _error = typeChecker([value], 0, componentName, location, propFullName + '<iteratorItem>', ReactPropTypesSecret);
        if (_error instanceof Error) {
          error = _error;
          return
        }
      });

      return error instanceof Error ? error : null;
    }
    return createChainableTypeChecker(validate);
  }

  function createMapOfTypeChecker(typeCheckers) {
    var validateIterable = createIterableOfTypeChecker(createTupleOfTypeChecker(typeCheckers));

    function validate(props, propName, componentName, location, propFullName) {
      if (!Array.isArray(typeCheckers)) {
        return new PropTypeError('Correct syntax is `PropTypes.mapOf([PropTypes.keyType, PropTypes.valueType])`.');
      }
      var keyChecker = typeCheckers[0];
      var valueChecker = typeCheckers[1];
      if (typeof Map !== 'function') {
        return new PropTypeError('Cannot use `PropTypes.mapOf` if the Map data structure is not present');
      }
      if (typeof keyChecker !== 'function' || typeof valueChecker !== 'function') {
        return new PropTypeError('Property `' + propFullName + '` of component `' + componentName + '` has invalid PropType notation inside mapOf.');
      }
      var propValue = props[propName];
      if (!isMap(propValue)) {
        var propType = getPropType(propValue);
        return new PropTypeError('Invalid ' + location + ' `' + propFullName + '` of type ' + ('`' + propType + '` supplied to `' + componentName + '`, expected a Map.'));
      }
      return validateIterable(props, propName, componentName, location, propFullName, ReactPropTypesSecret);
    }
    return createChainableTypeChecker(validate);
  }

  function createSetOfTypeChecker(typeChecker) {
    var validateIterable = createIterableOfTypeChecker(typeChecker);

    function validate(props, propName, componentName, location, propFullName) {
      if (typeof Set !== 'function') {
        return new PropTypeError('Cannot use `PropTypes.setOf` if the Set data structure is not present');
      }
      if (typeof typeChecker !== 'function') {
        return new PropTypeError('Property `' + propFullName + '` of component `' + componentName + '` has invalid PropType notation inside setOf.');
      }
      var propValue = props[propName];
      if (!isSet(propValue)) {
        var propType = getPropType(propValue);
        return new PropTypeError('Invalid ' + location + ' `' + propFullName + '` of type ' + ('`' + propType + '` supplied to `' + componentName + '`, expected a Set.'));
      }
      return validateIterable(props, propName, componentName, location, propFullName, ReactPropTypesSecret);
    }
    return createChainableTypeChecker(validate);
  }

  function createElementTypeChecker() {
    function validate(props, propName, componentName, location, propFullName) {
      var propValue = props[propName];
      if (!isValidElement(propValue)) {
        var propType = getPropType(propValue);
        return new PropTypeError('Invalid ' + location + ' `' + propFullName + '` of type ' + ('`' + propType + '` supplied to `' + componentName + '`, expected a single ReactElement.'));
      }
      return null;
    }
    return createChainableTypeChecker(validate);
  }

  function createElementTypeTypeChecker() {
    function validate(props, propName, componentName, location, propFullName) {
      var propValue = props[propName];
      if (!ReactIs.isValidElementType(propValue)) {
        var propType = getPropType(propValue);
        return new PropTypeError('Invalid ' + location + ' `' + propFullName + '` of type ' + ('`' + propType + '` supplied to `' + componentName + '`, expected a single ReactElement type.'));
      }
      return null;
    }
    return createChainableTypeChecker(validate);
  }

  function createInstanceTypeChecker(expectedClass) {
    function validate(props, propName, componentName, location, propFullName) {
      if (!(props[propName] instanceof expectedClass)) {
        var expectedClassName = expectedClass.name || ANONYMOUS;
        var actualClassName = getClassName(props[propName]);
        return new PropTypeError('Invalid ' + location + ' `' + propFullName + '` of type ' + ('`' + actualClassName + '` supplied to `' + componentName + '`, expected ') + ('instance of `' + expectedClassName + '`.'));
      }
      return null;
    }
    return createChainableTypeChecker(validate);
  }

  function createEnumTypeChecker(expectedValues) {
    if (!Array.isArray(expectedValues)) {
      if (process.env.NODE_ENV !== 'production') {
        if (arguments.length > 1) {
          printWarning(
            'Invalid arguments supplied to oneOf, expected an array, got ' + arguments.length + ' arguments. ' +
            'A common mistake is to write oneOf(x, y, z) instead of oneOf([x, y, z]).'
          );
        } else {
          printWarning('Invalid argument supplied to oneOf, expected an array.');
        }
      }
      return emptyFunctionThatReturnsNull;
    }

    function validate(props, propName, componentName, location, propFullName) {
      var propValue = props[propName];
      for (var i = 0; i < expectedValues.length; i++) {
        if (is(propValue, expectedValues[i])) {
          return null;
        }
      }

      var valuesString = JSON.stringify(expectedValues, function replacer(key, value) {
        var type = getPreciseType(value);
        if (type === 'symbol') {
          return String(value);
        }
        return value;
      });
      return new PropTypeError('Invalid ' + location + ' `' + propFullName + '` of value `' + String(propValue) + '` ' + ('supplied to `' + componentName + '`, expected one of ' + valuesString + '.'));
    }
    return createChainableTypeChecker(validate);
  }

  function createObjectOfTypeChecker(typeChecker) {
    function validate(props, propName, componentName, location, propFullName) {
      if (typeof typeChecker !== 'function') {
        return new PropTypeError('Property `' + propFullName + '` of component `' + componentName + '` has invalid PropType notation inside objectOf.');
      }
      var propValue = props[propName];
      var propType = getPropType(propValue);
      if (propType !== 'object') {
        return new PropTypeError('Invalid ' + location + ' `' + propFullName + '` of type ' + ('`' + propType + '` supplied to `' + componentName + '`, expected an object.'));
      }
      for (var key in propValue) {
        if (has(propValue, key)) {
          var error = typeChecker(propValue, key, componentName, location, propFullName + '.' + key, ReactPropTypesSecret);
          if (error instanceof Error) {
            return error;
          }
        }
      }
      return null;
    }
    return createChainableTypeChecker(validate);
  }

  function createUnionTypeChecker(arrayOfTypeCheckers) {
    if (!Array.isArray(arrayOfTypeCheckers)) {
      process.env.NODE_ENV !== 'production' ? printWarning('Invalid argument supplied to oneOfType, expected an instance of array.') : void 0;
      return emptyFunctionThatReturnsNull;
    }

    for (var i = 0; i < arrayOfTypeCheckers.length; i++) {
      var checker = arrayOfTypeCheckers[i];
      if (typeof checker !== 'function') {
        printWarning(
          'Invalid argument supplied to oneOfType. Expected an array of check functions, but ' +
          'received ' + getPostfixForTypeWarning(checker) + ' at index ' + i + '.'
        );
        return emptyFunctionThatReturnsNull;
      }
    }

    function validate(props, propName, componentName, location, propFullName) {
      var expectedTypes = [];
      for (var i = 0; i < arrayOfTypeCheckers.length; i++) {
        var checker = arrayOfTypeCheckers[i];
        var checkerResult = checker(props, propName, componentName, location, propFullName, ReactPropTypesSecret);
        if (checkerResult == null) {
          return null;
        }
        if (checkerResult.data.hasOwnProperty('expectedType')) {
          expectedTypes.push(checkerResult.data.expectedType);
        }
      }
      var expectedTypesMessage = (expectedTypes.length > 0) ? ', expected one of type [' + expectedTypes.join(', ') + ']': '';
      return new PropTypeError('Invalid ' + location + ' `' + propFullName + '` supplied to ' + ('`' + componentName + '`' + expectedTypesMessage + '.'));
    }
    return createChainableTypeChecker(validate);
  }

  function createNodeChecker() {
    function validate(props, propName, componentName, location, propFullName) {
      if (!isNode(props[propName])) {
        return new PropTypeError('Invalid ' + location + ' `' + propFullName + '` supplied to ' + ('`' + componentName + '`, expected a ReactNode.'));
      }
      return null;
    }
    return createChainableTypeChecker(validate);
  }

  function invalidValidatorError(componentName, location, propFullName, key, type) {
    return new PropTypeError(
      (componentName || 'React class') + ': ' + location + ' type `' + propFullName + '.' + key + '` is invalid; ' +
      'it must be a function, usually from the `prop-types` package, but received `' + type + '`.'
    );
  }

  function createShapeTypeChecker(shapeTypes) {
    function validate(props, propName, componentName, location, propFullName) {
      var propValue = props[propName];
      var propType = getPropType(propValue);
      if (propType !== 'object') {
        return new PropTypeError('Invalid ' + location + ' `' + propFullName + '` of type `' + propType + '` ' + ('supplied to `' + componentName + '`, expected `object`.'));
      }
      for (var key in shapeTypes) {
        var checker = shapeTypes[key];
        if (typeof checker !== 'function') {
          return invalidValidatorError(componentName, location, propFullName, key, getPreciseType(checker));
        }
        var error = checker(propValue, key, componentName, location, propFullName + '.' + key, ReactPropTypesSecret);
        if (error) {
          return error;
        }
      }
      return null;
    }
    return createChainableTypeChecker(validate);
  }

  function createStrictShapeTypeChecker(shapeTypes) {
    function validate(props, propName, componentName, location, propFullName) {
      var propValue = props[propName];
      var propType = getPropType(propValue);
      if (propType !== 'object') {
        return new PropTypeError('Invalid ' + location + ' `' + propFullName + '` of type `' + propType + '` ' + ('supplied to `' + componentName + '`, expected `object`.'));
      }
      // We need to check all keys in case some are required but missing from
      // props.
      var allKeys = assign({}, props[propName], shapeTypes);
      for (var key in allKeys) {
        var checker = shapeTypes[key];
        if (has(shapeTypes, key) && typeof checker !== 'function') {
          return invalidValidatorError(componentName, location, propFullName, key, getPreciseType(checker));
        }
        if (!checker) {
          return new PropTypeError(
            'Invalid ' + location + ' `' + propFullName + '` key `' + key + '` supplied to `' + componentName + '`.' +
            '\nBad object: ' + JSON.stringify(props[propName], null, '  ') +
            '\nValid keys: ' +  JSON.stringify(Object.keys(shapeTypes), null, '  ')
          );
        }
        var error = checker(propValue, key, componentName, location, propFullName + '.' + key, ReactPropTypesSecret);
        if (error) {
          return error;
        }
      }
      return null;
    }

    return createChainableTypeChecker(validate);
  }

  function isNode(propValue) {
    switch (typeof propValue) {
      case 'number':
      case 'string':
      case 'undefined':
        return true;
      case 'boolean':
        return !propValue;
      case 'object':
        if (Array.isArray(propValue)) {
          return propValue.every(isNode);
        }
        if (propValue === null || isValidElement(propValue)) {
          return true;
        }

        var iteratorFn = getIteratorFn(propValue);
        if (iteratorFn) {
          var iterator = iteratorFn.call(propValue);
          var step;
          if (iteratorFn !== propValue.entries) {
            while (!(step = iterator.next()).done) {
              if (!isNode(step.value)) {
                return false;
              }
            }
          } else {
            // Iterator will provide entry [k,v] tuples rather than values.
            while (!(step = iterator.next()).done) {
              var entry = step.value;
              if (entry) {
                if (!isNode(entry[1])) {
                  return false;
                }
              }
            }
          }
        } else {
          return false;
        }

        return true;
      default:
        return false;
    }
  }

  function isSymbol(propType, propValue) {
    // Native Symbol.
    if (propType === 'symbol') {
      return true;
    }

    // falsy value can't be a Symbol
    if (!propValue) {
      return false;
    }

    // 19.4.3.5 Symbol.prototype[@@toStringTag] === 'Symbol'
    if (propValue['@@toStringTag'] === 'Symbol') {
      return true;
    }

    // Fallback for non-spec compliant Symbols which are polyfilled.
    if (typeof Symbol === 'function' && propValue instanceof Symbol) {
      return true;
    }

    return false;
  }

  // Equivalent of `typeof` but with special handling for array and regexp.
  function getPropType(propValue) {
    var propType = typeof propValue;
    if (Array.isArray(propValue)) {
      return 'array';
    }
    if (propValue instanceof RegExp) {
      // Old webkits (at least until Android 4.0) return 'function' rather than
      // 'object' for typeof a RegExp. We'll normalize this here so that /bla/
      // passes PropTypes.object.
      return 'object';
    }
    if (isSymbol(propType, propValue)) {
      return 'symbol';
    }
    return propType;
  }

  // This handles more types than `getPropType`. Only used for error messages.
  // See `createPrimitiveTypeChecker`.
  function getPreciseType(propValue) {
    if (typeof propValue === 'undefined' || propValue === null) {
      return '' + propValue;
    }
    var propType = getPropType(propValue);
    if (propType === 'object') {
      if (propValue instanceof Date) {
        return 'date';
      } else if (propValue instanceof RegExp) {
        return 'regexp';
      }
    }
    return propType;
  }

  // Returns a string that is postfixed to a warning about an invalid type.
  // For example, "undefined" or "of type array"
  function getPostfixForTypeWarning(value) {
    var type = getPreciseType(value);
    switch (type) {
      case 'array':
      case 'object':
        return 'an ' + type;
      case 'boolean':
      case 'date':
      case 'regexp':
        return 'a ' + type;
      default:
        return type;
    }
  }

  // Returns class name of the object, if any.
  function getClassName(propValue) {
    if (!propValue.constructor || !propValue.constructor.name) {
      return ANONYMOUS;
    }
    return propValue.constructor.name;
  }

  ReactPropTypes.checkPropTypes = checkPropTypes;
  ReactPropTypes.resetWarningCache = checkPropTypes.resetWarningCache;
  ReactPropTypes.PropTypes = ReactPropTypes;

  return ReactPropTypes;
};