Function patternDirective

test/angular/1.6/angular.js:34507–34536

()

 * </example>
 */
var patternDirective = function() {
  return {
    restrict: 'A',
    require: '?ngModel',
    link: function(scope, elm, attr, ctrl) {
      if (!ctrl) return;

      var regexp, patternExp = attr.ngPattern || attr.pattern;
      attr.$observe('pattern', function(regex) {
        if (isString(regex) && regex.length > 0) {
          regex = new RegExp('^' + regex + '$');
        }

        if (regex && !regex.test) {
          throw minErr('ngPattern')('noregexp',
            'Expected {0} to be a RegExp but was {1}. Element: {2}', patternExp,
            regex, startingTag(elm));
        }

        regexp = regex || undefined;
        ctrl.$validate();
      });

      ctrl.$validators.pattern = function(modelValue, viewValue) {
        // HTML5 pattern constraint validates the input value, so we validate the viewValue
        return ctrl.$isEmpty(viewValue) || isUndefined(regexp) || regexp.test(viewValue);
      };
    }
  };
};

/**
 * @ngdoc directive