feat(typeahead): add 'is-open' support

- Adds support for checking the toggled state of the dropdown

Closes #4760
Closes #4779

Author: chenyuzhcy

Diff for: src/typeahead/docs/readme.md

@@ -78,3 +78,7 @@ The typeahead directives provide several attributes:
 * `typeahead-focus-on-select`
    _(Defaults: true) :
    On selection, focus the input element the typeahead directive is associated with
+
+* `typeahead-is-open` <i class="glyphicon glyphicon-eye-open"></i>
+   _(Defaults: angular.noop)_ :
+   Binding to a variable that indicates if dropdown is open

Diff for: src/typeahead/test/typeahead.spec.js

@@ -588,6 +588,78 @@ describe('typeahead tests', function() {
     });
   });
 
+  describe('is-open indicator', function () {
+      var element;
+
+      beforeEach(function () {
+          element = prepareInputEl('<div><input ng-model="result" uib-typeahead="item for item in source | filter:$viewValue" typeahead-is-open="isOpen"></div>');
+      });
+
+      it('should bind is-open indicator as true when matches are returned', function () {
+          expect($scope.isOpen).toBeFalsy();
+          changeInputValueTo(element, 'b');
+          expect($scope.isOpen).toBeTruthy();
+      });
+
+      it('should bind is-open indicator as false when no matches returned', function () {
+          expect($scope.isOpen).toBeFalsy();
+          changeInputValueTo(element, 'b');
+          expect($scope.isOpen).toBeTruthy();
+          changeInputValueTo(element, 'not match');
+          expect($scope.isOpen).toBeFalsy();
+      });
+
+      it('should bind is-open indicator as false when a match is clicked', function () {
+          expect($scope.isOpen).toBeFalsy();
+          changeInputValueTo(element, 'b');
+          expect($scope.isOpen).toBeTruthy();
+          var match = findMatches(element).find('a').eq(0);
+
+          match.click();
+          $scope.$digest();
+          expect($scope.isOpen).toBeFalsy();
+      });
+      it('should bind is-open indicator as false when click outside', function () {
+          expect($scope.isOpen).toBeFalsy();
+          changeInputValueTo(element, 'b');
+          expect($scope.isOpen).toBeTruthy();
+          $document.find('body').click();
+          $scope.$digest();
+          expect($scope.isOpen).toBeFalsy();
+      });
+
+      it('should bind is-open indicator as false on enter', function () {
+          expect($scope.isOpen).toBeFalsy();
+          changeInputValueTo(element, 'b');
+          expect($scope.isOpen).toBeTruthy();
+          triggerKeyDown(element, 13);
+          expect($scope.isOpen).toBeFalsy();
+      });
+
+      it('should bind is-open indicator as false on tab', function () {
+          expect($scope.isOpen).toBeFalsy();
+          changeInputValueTo(element, 'b');
+          expect($scope.isOpen).toBeTruthy();
+          triggerKeyDown(element, 9);
+          expect($scope.isOpen).toBeFalsy();
+      });
+
+      it('should bind is-open indicator as false on escape key', function () {
+          expect($scope.isOpen).toBeFalsy();
+          changeInputValueTo(element, 'b');
+          expect($scope.isOpen).toBeTruthy();
+          triggerKeyDown(element, 27);
+          expect($scope.isOpen).toBeFalsy();
+      });
+
+      it('should bind is-open indicator as false input value smaller than a defined threshold', function () {
+          var element = prepareInputEl('<div><input ng-model="result" uib-typeahead="item for item in source | filter:$viewValue" typeahead-is-open="isToggled" typeahead-min-length="2"></div>');
+          expect($scope.isToggled).toBeFalsy();
+          changeInputValueTo(element, 'b');
+          expect($scope.isToggled).toBeFalsy();
+      });
+  });
+
   describe('pop-up interaction', function() {
     var element;
 

Diff for: src/typeahead/typeahead.js

@@ -68,6 +68,9 @@ angular.module('ui.bootstrap.typeahead', ['ui.bootstrap.position'])
     //If input matches an item of the list exactly, select it automatically
     var selectOnExact = attrs.typeaheadSelectOnExact ? originalScope.$eval(attrs.typeaheadSelectOnExact) : false;
 
+    //binding to a variable that indicates if dropdown is open
+    var isOpenSetter = $parse(attrs.typeaheadIsOpen).assign || angular.noop;
+
     //INTERNAL VARIABLES
 
     //model setter executed upon match selection
@@ -117,7 +120,8 @@ angular.module('ui.bootstrap.typeahead', ['ui.bootstrap.position'])
       select: 'select(activeIdx)',
       'move-in-progress': 'moveInProgress',
       query: 'query',
-      position: 'position'
+      position: 'position',
+      'assign-is-open': 'assignIsOpen(isOpen)'
     });
     //custom item template
     if (angular.isDefined(attrs.typeaheadTemplateUrl)) {
@@ -268,6 +272,10 @@ angular.module('ui.bootstrap.typeahead', ['ui.bootstrap.position'])
 
     resetMatches();
 
+    scope.assignIsOpen = function (isOpen) {
+        isOpenSetter(originalScope, isOpen);
+    };
+
     scope.select = function(activeIdx) {
       //called from within the $digest() cycle
       var locals = {};
@@ -463,7 +471,8 @@ angular.module('ui.bootstrap.typeahead', ['ui.bootstrap.position'])
         active: '=',
         position: '&',
         moveInProgress: '=',
-        select: '&'
+        select: '&',
+        assignIsOpen: '&',
       },
       replace: true,
       templateUrl: function(element, attrs) {
@@ -472,8 +481,10 @@ angular.module('ui.bootstrap.typeahead', ['ui.bootstrap.position'])
       link: function(scope, element, attrs) {
         scope.templateUrl = attrs.templateUrl;
 
-        scope.isOpen = function() {
-          return scope.matches.length > 0;
+        scope.isOpen = function () {
+          var isDropdownOpen = scope.matches.length > 0;
+          scope.assignIsOpen({ isOpen: isDropdownOpen });
+          return isDropdownOpen;
         };
 
         scope.isActive = function(matchIdx) {