messages.js

'use strict';

var forEach;
var isArray;
var isString;
var jqLite;

/**
 * @ngdoc module
 * @name ngMessages
 * @description
 *
 * The `ngMessages` module provides enhanced support for displaying messages within templates
 * (typically within forms or when rendering message objects that return key/value data).
 * Instead of relying on JavaScript code and/or complex ng-if statements within your form template to
 * show and hide error messages specific to the state of an input field, the `ngMessages` and
 * `ngMessage` directives are designed to handle the complexity, inheritance and priority
 * sequencing based on the order of how the messages are defined in the template.
 *
 * Currently, the ngMessages module only contains the code for the `ngMessages`, `ngMessagesInclude`
 * `ngMessage`, `ngMessageExp` and `ngMessageDefault` directives.
 *
 * ## Usage
 * The `ngMessages` directive allows keys in a key/value collection to be associated with a child element
 * (or 'message') that will show or hide based on the truthiness of that key's value in the collection. A common use
 * case for `ngMessages` is to display error messages for inputs using the `$error` object exposed by the
 * {@link ngModel ngModel} directive.
 *
 * The child elements of the `ngMessages` directive are matched to the collection keys by a `ngMessage` or
 * `ngMessageExp` directive. The value of these attributes must match a key in the collection that is provided by
 * the `ngMessages` directive.
 *
 * Consider the following example, which illustrates a typical use case of `ngMessages`. Within the form `myForm` we
 * have a text input named `myField` which is bound to the scope variable `field` using the {@link ngModel ngModel}
 * directive.
 *
 * The `myField` field is a required input of type `email` with a maximum length of 15 characters.
 *
 * ```html
 * <form name="myForm">
 *   <label>
 *     Enter text:
 *     <input type="email" ng-model="field" name="myField" required maxlength="15" />
 *   </label>
 *   <div ng-messages="myForm.myField.$error" role="alert">
 *     <div ng-message="required">Please enter a value for this field.</div>
 *     <div ng-message="email">This field must be a valid email address.</div>
 *     <div ng-message="maxlength">This field can be at most 15 characters long.</div>
 *   </div>
 * </form>
 * ```
 *
 * In order to show error messages corresponding to `myField` we first create an element with an `ngMessages` attribute
 * set to the `$error` object owned by the `myField` input in our `myForm` form.
 *
 * Within this element we then create separate elements for each of the possible errors that `myField` could have.
 * The `ngMessage` attribute is used to declare which element(s) will appear for which error - for example,
 * setting `ng-message="required"` specifies that this particular element should be displayed when there
 * is no value present for the required field `myField` (because the key `required` will be `true` in the object
 * `myForm.myField.$error`).
 *
 * ### Message order
 *
 * By default, `ngMessages` will only display one message for a particular key/value collection at any time. If more
 * than one message (or error) key is currently true, then which message is shown is determined by the order of messages
 * in the HTML template code (messages declared first are prioritised). This mechanism means the developer does not have
 * to prioritize messages using custom JavaScript code.
 *
 * Given the following error object for our example (which informs us that the field `myField` currently has both the
 * `required` and `email` errors):
 *
 * ```javascript
 * <!-- keep in mind that ngModel automatically sets these error flags -->
 * myField.$error = { required : true, email: true, maxlength: false };
 * ```
 * The `required` message will be displayed to the user since it appears before the `email` message in the DOM.
 * Once the user types a single character, the `required` message will disappear (since the field now has a value)
 * but the `email` message will be visible because it is still applicable.
 *
 * ### Displaying multiple messages at the same time
 *
 * While `ngMessages` will by default only display one error element at a time, the `ng-messages-multiple` attribute can
 * be applied to the `ngMessages` container element to cause it to display all applicable error messages at once:
 *
 * ```html
 * <!-- attribute-style usage -->
 * <div ng-messages="myForm.myField.$error" ng-messages-multiple>...</div>
 *
 * <!-- element-style usage -->
 * <ng-messages for="myForm.myField.$error" multiple>...</ng-messages>
 * ```
 *
 * ## Reusing and Overriding Messages
 * In addition to prioritization, ngMessages also allows for including messages from a remote or an inline
 * template. This allows for generic collection of messages to be reused across multiple parts of an
 * application.
 *
 * ```html
 * <script type="text/ng-template" id="error-messages">
 *   <div ng-message="required">This field is required</div>
 *   <div ng-message="minlength">This field is too short</div>
 * </script>
 *
 * <div ng-messages="myForm.myField.$error" role="alert">
 *   <div ng-messages-include="error-messages"></div>
 * </div>
 * ```
 *
 * However, including generic messages may not be useful enough to match all input fields, therefore,
 * `ngMessages` provides the ability to override messages defined in the remote template by redefining
 * them within the directive container.
 *
 * ```html
 * <!-- a generic template of error messages known as "my-custom-messages" -->
 * <script type="text/ng-template" id="my-custom-messages">
 *   <div ng-message="required">This field is required</div>
 *   <div ng-message="minlength">This field is too short</div>
 * </script>
 *
 * <form name="myForm">
 *   <label>
 *     Email address
 *     <input type="email"
 *            id="email"
 *            name="myEmail"
 *            ng-model="email"
 *            minlength="5"
 *            required />
 *   </label>
 *   <!-- any ng-message elements that appear BEFORE the ng-messages-include will
 *        override the messages present in the ng-messages-include template -->
 *   <div ng-messages="myForm.myEmail.$error" role="alert">
 *     <!-- this required message has overridden the template message -->
 *     <div ng-message="required">You did not enter your email address</div>
 *
 *     <!-- this is a brand new message and will appear last in the prioritization -->
 *     <div ng-message="email">Your email address is invalid</div>
 *
 *     <!-- and here are the generic error messages -->
 *     <div ng-messages-include="my-custom-messages"></div>
 *   </div>
 * </form>
 * ```
 *
 * In the example HTML code above the message that is set on required will override the corresponding
 * required message defined within the remote template. Therefore, with particular input fields (such
 * email addresses, date fields, autocomplete inputs, etc...), specialized error messages can be applied
 * while more generic messages can be used to handle other, more general input errors.
 *
 * ## Dynamic Messaging
 * ngMessages also supports using expressions to dynamically change key values. Using arrays and
 * repeaters to list messages is also supported. This means that the code below will be able to
 * fully adapt itself and display the appropriate message when any of the expression data changes:
 *
 * ```html
 * <form name="myForm">
 *   <label>
 *     Email address
 *     <input type="email"
 *            name="myEmail"
 *            ng-model="email"
 *            minlength="5"
 *            required />
 *   </label>
 *   <div ng-messages="myForm.myEmail.$error" role="alert">
 *     <div ng-message="required">You did not enter your email address</div>
 *     <div ng-repeat="errorMessage in errorMessages">
 *       <!-- use ng-message-exp for a message whose key is given by an expression -->
 *       <div ng-message-exp="errorMessage.type">{{ errorMessage.text }}</div>
 *     </div>
 *   </div>
 * </form>
 * ```
 *
 * The `errorMessage.type` expression can be a string value or it can be an array so
 * that multiple errors can be associated with a single error message:
 *
 * ```html
 *   <label>
 *     Email address
 *     <input type="email"
 *            ng-model="data.email"
 *            name="myEmail"
 *            ng-minlength="5"
 *            ng-maxlength="100"
 *            required />
 *   </label>
 *   <div ng-messages="myForm.myEmail.$error" role="alert">
 *     <div ng-message-exp="'required'">You did not enter your email address</div>
 *     <div ng-message-exp="['minlength', 'maxlength']">
 *       Your email must be between 5 and 100 characters long
 *     </div>
 *   </div>
 * ```
 *
 * Feel free to use other structural directives such as ng-if and ng-switch to further control
 * what messages are active and when. Be careful, if you place ng-message on the same element
 * as these structural directives, AngularJS may not be able to determine if a message is active
 * or not. Therefore it is best to place the ng-message on a child element of the structural
 * directive.
 *
 * ```html
 * <div ng-messages="myForm.myEmail.$error" role="alert">
 *   <div ng-if="showRequiredError">
 *     <div ng-message="required">Please enter something</div>
 *   </div>
 * </div>
 * ```
 *
 * ## Animations
 * If the `ngAnimate` module is active within the application then the `ngMessages`, `ngMessage` and
 * `ngMessageExp` directives will trigger animations whenever any messages are added and removed from
 * the DOM by the `ngMessages` directive.
 *
 * Whenever the `ngMessages` directive contains one or more visible messages then the `.ng-active` CSS
 * class will be added to the element. The `.ng-inactive` CSS class will be applied when there are no
 * messages present. Therefore, CSS transitions and keyframes as well as JavaScript animations can
 * hook into the animations whenever these classes are added/removed.
 *
 * Let's say that our HTML code for our messages container looks like so:
 *
 * ```html
 * <div ng-messages="myMessages" class="my-messages" role="alert">
 *   <div ng-message="alert" class="some-message">...</div>
 *   <div ng-message="fail" class="some-message">...</div>
 * </div>
 * ```
 *
 * Then the CSS animation code for the message container looks like so:
 *
 * ```css
 * .my-messages {
 *   transition:1s linear all;
 * }
 * .my-messages.ng-active {
 *   // messages are visible
 * }
 * .my-messages.ng-inactive {
 *   // messages are hidden
 * }
 * ```
 *
 * Whenever an inner message is attached (becomes visible) or removed (becomes hidden) then the enter
 * and leave animation is triggered for each particular element bound to the `ngMessage` directive.
 *
 * Therefore, the CSS code for the inner messages looks like so:
 *
 * ```css
 * .some-message {
 *   transition:1s linear all;
 * }
 *
 * .some-message.ng-enter {}
 * .some-message.ng-enter.ng-enter-active {}
 *
 * .some-message.ng-leave {}
 * .some-message.ng-leave.ng-leave-active {}
 * ```
 *
 * {@link ngAnimate See the ngAnimate docs} to learn how to use JavaScript animations or to learn
 * more about ngAnimate.
 *
 * ## Displaying a default message
 * If the ngMessages renders no inner ngMessage directive (that is to say when the key values does not
 * match the attribute value present on each ngMessage directive), then it will render a default message
 * using the {@link ngMessageDefault} directive.
 *
 * ```html
 * <div ng-messages="myForm.myField.$error" role="alert">
 *   <div ng-message="required">This field is required</div>
 *   <div ng-message="minlength">This field is too short</div>
 *   <div ng-message-default>This field has an input error</div>
 * </div>
 * ```
 */
angular.module('ngMessages', [], function initAngularHelpers() {
  // Access helpers from AngularJS core.
  // Do it inside a `config` block to ensure `window.angular` is available.
  forEach = angular.forEach;
  isArray = angular.isArray;
  isString = angular.isString;
  jqLite = angular.element;
})
  .info({ angularVersion: '"NG_VERSION_FULL"' })

  /**
   * @ngdoc directive
   * @module ngMessages
   * @name ngMessages
   * @restrict AE
   *
   * @description
   * `ngMessages` is a directive that is designed to show and hide messages based on the state
   * of a key/value object that it listens on. The directive itself complements error message
   * reporting with the `ngModel` $error object (which stores a key/value state of validation errors).
   *
   * `ngMessages` manages the state of internal messages within its container element. The internal
   * messages use the `ngMessage` directive and will be inserted/removed from the page depending
   * on if they're present within the key/value object. By default, only one message will be displayed
   * at a time and this depends on the prioritization of the messages within the template. (This can
   * be changed by using the `ng-messages-multiple` or `multiple` attribute on the directive container.)
   *
   * A remote template can also be used (With {@link ngMessagesInclude}) to promote message
   * reusability and messages can also be overridden.
   *
   * A default message can also be displayed when no `ngMessage` directive is inserted, using the
   * {@link ngMessageDefault} directive.
   *
   * {@link module:ngMessages Click here} to learn more about `ngMessages` and `ngMessage`.
   *
   * @usage
   * ```html
   * <!-- using attribute directives -->
   * <ANY ng-messages="expression" role="alert">
   *   <ANY ng-message="stringValue">...</ANY>
   *   <ANY ng-message="stringValue1, stringValue2, ...">...</ANY>
   *   <ANY ng-message-exp="expressionValue">...</ANY>
   *   <ANY ng-message-default>...</ANY>
   * </ANY>
   *
   * <!-- or by using element directives -->
   * <ng-messages for="expression" role="alert">
   *   <ng-message when="stringValue">...</ng-message>
   *   <ng-message when="stringValue1, stringValue2, ...">...</ng-message>
   *   <ng-message when-exp="expressionValue">...</ng-message>
   *   <ng-message-default>...</ng-message-default>
   * </ng-messages>
   * ```
   *
   * @param {string} ngMessages an AngularJS expression evaluating to a key/value object
   *                 (this is typically the $error object on an ngModel instance).
   * @param {string=} ngMessagesMultiple|multiple when set, all messages will be displayed with true
   *
   * @example
   * <example name="ngMessages-directive" module="ngMessagesExample"
   *          deps="angular-messages.js"
   *          animations="true" fixBase="true">
   *   <file name="index.html">
   *     <form name="myForm">
   *       <label>
   *         Enter your name:
   *         <input type="text"
   *                name="myName"
   *                ng-model="name"
   *                ng-minlength="5"
   *                ng-maxlength="20"
   *                required />
   *       </label>
   *       <pre>myForm.myName.$error = {{ myForm.myName.$error | json }}</pre>
   *
   *       <div ng-messages="myForm.myName.$error" style="color:maroon" role="alert">
   *         <div ng-message="required">You did not enter a field</div>
   *         <div ng-message="minlength">Your field is too short</div>
   *         <div ng-message="maxlength">Your field is too long</div>
   *         <div ng-message-default>This field has an input error</div>
   *       </div>
   *     </form>
   *   </file>
   *   <file name="script.js">
   *     angular.module('ngMessagesExample', ['ngMessages']);
   *   </file>
   * </example>
   */
  .directive('ngMessages', ['$animate', function($animate) {
    var ACTIVE_CLASS = 'ng-active';
    var INACTIVE_CLASS = 'ng-inactive';

    return {
      require: 'ngMessages',
      restrict: 'AE',
      controller: ['$element', '$scope', '$attrs', function NgMessagesCtrl($element, $scope, $attrs) {
        var ctrl = this;
        var latestKey = 0;
        var nextAttachId = 0;

        this.getAttachId = function getAttachId() { return nextAttachId++; };

        var messages = this.messages = {};
        var renderLater, cachedCollection;

        this.render = function(collection) {
          collection = collection || {};

          renderLater = false;
          cachedCollection = collection;

          // this is true if the attribute is empty or if the attribute value is truthy
          var multiple = isAttrTruthy($scope, $attrs.ngMessagesMultiple) ||
                         isAttrTruthy($scope, $attrs.multiple);

          var unmatchedMessages = [];
          var matchedKeys = {};
          var messageItem = ctrl.head;
          var messageFound = false;
          var totalMessages = 0;

          // we use != instead of !== to allow for both undefined and null values
          while (messageItem != null) {
            totalMessages++;
            var messageCtrl = messageItem.message;

            var messageUsed = false;
            if (!messageFound) {
              forEach(collection, function(value, key) {
                if (!messageUsed && truthy(value) && messageCtrl.test(key)) {
                  // this is to prevent the same error name from showing up twice
                  if (matchedKeys[key]) return;
                  matchedKeys[key] = true;

                  messageUsed = true;
                  messageCtrl.attach();
                }
              });
            }

            if (messageUsed) {
              // unless we want to display multiple messages then we should
              // set a flag here to avoid displaying the next message in the list
              messageFound = !multiple;
            } else {
              unmatchedMessages.push(messageCtrl);
            }

            messageItem = messageItem.next;
          }

          forEach(unmatchedMessages, function(messageCtrl) {
            messageCtrl.detach();
          });

          if (unmatchedMessages.length !== totalMessages) {
            // Unset default message if set
            if (ctrl.default) ctrl.default.detach();

            $animate.setClass($element, ACTIVE_CLASS, INACTIVE_CLASS);
          } else {

            // Set default message if no other matched
            if (ctrl.default) ctrl.default.attach();

            $animate.setClass($element, INACTIVE_CLASS, ACTIVE_CLASS);
          }
        };

        $scope.$watchCollection($attrs.ngMessages || $attrs['for'], ctrl.render);

        this.reRender = function() {
          if (!renderLater) {
            renderLater = true;
            $scope.$evalAsync(function() {
              if (renderLater && cachedCollection) {
                ctrl.render(cachedCollection);
              }
            });
          }
        };

        this.register = function(comment, messageCtrl, isDefault) {
          if (isDefault) {
            ctrl.default = messageCtrl;
          } else {
            var nextKey = latestKey.toString();
            messages[nextKey] = {
              message: messageCtrl
            };
            insertMessageNode($element[0], comment, nextKey);
            comment.$$ngMessageNode = nextKey;
            latestKey++;
          }

          ctrl.reRender();
        };

        this.deregister = function(comment, isDefault) {
          if (isDefault) {
            delete ctrl.default;
          } else {
            var key = comment.$$ngMessageNode;
            delete comment.$$ngMessageNode;
            removeMessageNode($element[0], comment, key);
            delete messages[key];
          }
          ctrl.reRender();
        };

        function findPreviousMessage(parent, comment) {
          var prevNode = comment;
          var parentLookup = [];

          while (prevNode && prevNode !== parent) {
            var prevKey = prevNode.$$ngMessageNode;
            if (prevKey && prevKey.length) {
              return messages[prevKey];
            }

            // dive deeper into the DOM and examine its children for any ngMessage
            // comments that may be in an element that appears deeper in the list
            if (prevNode.childNodes.length && parentLookup.indexOf(prevNode) === -1) {
              parentLookup.push(prevNode);
              prevNode = prevNode.childNodes[prevNode.childNodes.length - 1];
            } else if (prevNode.previousSibling) {
              prevNode = prevNode.previousSibling;
            } else {
              prevNode = prevNode.parentNode;
              parentLookup.push(prevNode);
            }
          }
        }

        function insertMessageNode(parent, comment, key) {
          var messageNode = messages[key];
          if (!ctrl.head) {
            ctrl.head = messageNode;
          } else {
            var match = findPreviousMessage(parent, comment);
            if (match) {
              messageNode.next = match.next;
              match.next = messageNode;
            } else {
              messageNode.next = ctrl.head;
              ctrl.head = messageNode;
            }
          }
        }

        function removeMessageNode(parent, comment, key) {
          var messageNode = messages[key];

          // This message node may have already been removed by a call to deregister()
          if (!messageNode) return;

          var match = findPreviousMessage(parent, comment);
          if (match) {
            match.next = messageNode.next;
          } else {
            ctrl.head = messageNode.next;
          }
        }
      }]
    };

    function isAttrTruthy(scope, attr) {
     return (isString(attr) && attr.length === 0) || //empty attribute
            truthy(scope.$eval(attr));
    }

    function truthy(val) {
      return isString(val) ? val.length : !!val;
    }
  }])

  /**
   * @ngdoc directive
   * @name ngMessagesInclude
   * @restrict AE
   * @scope
   *
   * @description
   * `ngMessagesInclude` is a directive with the purpose to import existing ngMessage template
   * code from a remote template and place the downloaded template code into the exact spot
   * that the ngMessagesInclude directive is placed within the ngMessages container. This allows
   * for a series of pre-defined messages to be reused and also allows for the developer to
   * determine what messages are overridden due to the placement of the ngMessagesInclude directive.
   *
   * @usage
   * ```html
   * <!-- using attribute directives -->
   * <ANY ng-messages="expression" role="alert">
   *   <ANY ng-messages-include="remoteTplString">...</ANY>
   * </ANY>
   *
   * <!-- or by using element directives -->
   * <ng-messages for="expression" role="alert">
   *   <ng-messages-include src="expressionValue1">...</ng-messages-include>
   * </ng-messages>
   * ```
   *
   * {@link module:ngMessages Click here} to learn more about `ngMessages` and `ngMessage`.
   *
   * @param {string} ngMessagesInclude|src a string value corresponding to the remote template.
   */
  .directive('ngMessagesInclude',
    ['$templateRequest', '$document', '$compile', function($templateRequest, $document, $compile) {

    return {
      restrict: 'AE',
      require: '^^ngMessages', // we only require this for validation sake
      link: function($scope, element, attrs) {
        var src = attrs.ngMessagesInclude || attrs.src;
        $templateRequest(src).then(function(html) {
          if ($scope.$$destroyed) return;

          if (isString(html) && !html.trim()) {
            // Empty template - nothing to compile
            replaceElementWithMarker(element, src);
          } else {
            // Non-empty template - compile and link
            $compile(html)($scope, function(contents) {
              element.after(contents);
              replaceElementWithMarker(element, src);
            });
          }
        });
      }
    };

    // Helpers
    function replaceElementWithMarker(element, src) {
      // A comment marker is placed for debugging purposes
      var comment = $compile.$$createComment ?
          $compile.$$createComment('ngMessagesInclude', src) :
          $document[0].createComment(' ngMessagesInclude: ' + src + ' ');
      var marker = jqLite(comment);
      element.after(marker);

      // Don't pollute the DOM anymore by keeping an empty directive element
      element.remove();
    }
  }])

  /**
   * @ngdoc directive
   * @name ngMessage
   * @restrict AE
   * @scope
   * @priority 1
   *
   * @description
   * `ngMessage` is a directive with the purpose to show and hide a particular message.
   * For `ngMessage` to operate, a parent `ngMessages` directive on a parent DOM element
   * must be situated since it determines which messages are visible based on the state
   * of the provided key/value map that `ngMessages` listens on.
   *
   * More information about using `ngMessage` can be found in the
   * {@link module:ngMessages `ngMessages` module documentation}.
   *
   * @usage
   * ```html
   * <!-- using attribute directives -->
   * <ANY ng-messages="expression" role="alert">
   *   <ANY ng-message="stringValue">...</ANY>
   *   <ANY ng-message="stringValue1, stringValue2, ...">...</ANY>
   * </ANY>
   *
   * <!-- or by using element directives -->
   * <ng-messages for="expression" role="alert">
   *   <ng-message when="stringValue">...</ng-message>
   *   <ng-message when="stringValue1, stringValue2, ...">...</ng-message>
   * </ng-messages>
   * ```
   *
   * @param {expression} ngMessage|when a string value corresponding to the message key.
   */
  .directive('ngMessage', ngMessageDirectiveFactory())


  /**
   * @ngdoc directive
   * @name ngMessageExp
   * @restrict AE
   * @priority 1
   * @scope
   *
   * @description
   * `ngMessageExp` is the same as {@link directive:ngMessage `ngMessage`}, but instead of a static
   * value, it accepts an expression to be evaluated for the message key.
   *
   * @usage
   * ```html
   * <!-- using attribute directives -->
   * <ANY ng-messages="expression">
   *   <ANY ng-message-exp="expressionValue">...</ANY>
   * </ANY>
   *
   * <!-- or by using element directives -->
   * <ng-messages for="expression">
   *   <ng-message when-exp="expressionValue">...</ng-message>
   * </ng-messages>
   * ```
   *
   * {@link module:ngMessages Click here} to learn more about `ngMessages` and `ngMessage`.
   *
   * @param {expression} ngMessageExp|whenExp an expression value corresponding to the message key.
   */
  .directive('ngMessageExp', ngMessageDirectiveFactory())

  /**
   * @ngdoc directive
   * @name ngMessageDefault
   * @restrict AE
   * @scope
   *
   * @description
   * `ngMessageDefault` is a directive with the purpose to show and hide a default message for
   * {@link ngMessages}, when none of provided messages matches.
   *
   * More information about using `ngMessageDefault` can be found in the
   * {@link module:ngMessages `ngMessages` module documentation}.
   *
   * @usage
   * ```html
   * <!-- using attribute directives -->
   * <ANY ng-messages="expression" role="alert">
   *   <ANY ng-message="stringValue">...</ANY>
   *   <ANY ng-message="stringValue1, stringValue2, ...">...</ANY>
   *   <ANY ng-message-default>...</ANY>
   * </ANY>
   *
   * <!-- or by using element directives -->
   * <ng-messages for="expression" role="alert">
   *   <ng-message when="stringValue">...</ng-message>
   *   <ng-message when="stringValue1, stringValue2, ...">...</ng-message>
   *   <ng-message-default>...</ng-message-default>
   * </ng-messages>
   *
  */
  .directive('ngMessageDefault', ngMessageDirectiveFactory(true));

function ngMessageDirectiveFactory(isDefault) {
  return ['$animate', function($animate) {
    return {
      restrict: 'AE',
      transclude: 'element',
      priority: 1, // must run before ngBind, otherwise the text is set on the comment
      terminal: true,
      require: '^^ngMessages',
      link: function(scope, element, attrs, ngMessagesCtrl, $transclude) {
        var commentNode, records, staticExp, dynamicExp;

        if (!isDefault) {
          commentNode = element[0];
          staticExp = attrs.ngMessage || attrs.when;
          dynamicExp = attrs.ngMessageExp || attrs.whenExp;

          var assignRecords = function(items) {
            records = items
                ? (isArray(items)
                      ? items
                      : items.split(/[\s,]+/))
                : null;
            ngMessagesCtrl.reRender();
          };

          if (dynamicExp) {
            assignRecords(scope.$eval(dynamicExp));
            scope.$watchCollection(dynamicExp, assignRecords);
          } else {
            assignRecords(staticExp);
          }
        }

        var currentElement, messageCtrl;
        ngMessagesCtrl.register(commentNode, messageCtrl = {
          test: function(name) {
            return contains(records, name);
          },
          attach: function() {
            if (!currentElement) {
              $transclude(function(elm, newScope) {
                $animate.enter(elm, null, element);
                currentElement = elm;

                // Each time we attach this node to a message we get a new id that we can match
                // when we are destroying the node later.
                var $$attachId = currentElement.$$attachId = ngMessagesCtrl.getAttachId();

                // in the event that the element or a parent element is destroyed
                // by another structural directive then it's time
                // to deregister the message from the controller
                currentElement.on('$destroy', function() {
                  // If the message element was removed via a call to `detach` then `currentElement` will be null
                  // So this handler only handles cases where something else removed the message element.
                  if (currentElement && currentElement.$$attachId === $$attachId) {
                    ngMessagesCtrl.deregister(commentNode, isDefault);
                    messageCtrl.detach();
                  }
                  newScope.$destroy();
                });
              });
            }
          },
          detach: function() {
            if (currentElement) {
              var elm = currentElement;
              currentElement = null;
              $animate.leave(elm);
            }
          }
        }, isDefault);

        // We need to ensure that this directive deregisters itself when it no longer exists
        // Normally this is done when the attached element is destroyed; but if this directive
        // gets removed before we attach the message to the DOM there is nothing to watch
        // in which case we must deregister when the containing scope is destroyed.
        scope.$on('$destroy', function() {
          ngMessagesCtrl.deregister(commentNode, isDefault);
        });
      }
    };
  }];

  function contains(collection, key) {
    if (collection) {
      return isArray(collection)
          ? collection.indexOf(key) >= 0
          : collection.hasOwnProperty(key);
    }
  }
}