feat(autocomplete): add md-require-match validator.

Fixes #2492.

Closes #8344

src/components/autocomplete/autocomplete.spec.js

@@ -1248,6 +1248,51 @@ describe('<md-autocomplete>', function() {
     }));
   });
 
+  describe('when requiring a match', function() {
+
+    it('should correctly update the validity', inject(function($timeout) {
+      var scope = createScope();
+      var template = '\
+          <form name="form">\
+            <md-autocomplete\
+                md-input-name="autocomplete"\
+                md-selected-item="selectedItem"\
+                md-search-text="searchText"\
+                md-items="item in match(searchText)"\
+                md-item-text="item.display"\
+                placeholder="placeholder"\
+                md-require-match="true">\
+              <span md-highlight-text="searchText">{{item.display}}</span>\
+            </md-autocomplete>\
+          </form>';
+      var element = compile(template, scope);
+      var ctrl = element.find('md-autocomplete').controller('mdAutocomplete');
+
+      element.scope().searchText = 'fo';
+      $timeout.flush();
+
+      ctrl.select(0);
+      $timeout.flush();
+
+      expect(scope.searchText).toBe('foo');
+      expect(scope.selectedItem).not.toBeNull();
+      expect(scope.selectedItem.display).toBe('foo');
+      expect(scope.match(scope.searchText).length).toBe(1);
+
+      expect(scope.form.autocomplete.$error['md-require-match']).toBeFalsy();
+
+      ctrl.clear();
+
+      scope.$apply();
+
+      expect(scope.searchText).toBe('');
+      expect(scope.selectedItem).toBe(null);
+      expect(scope.form.autocomplete.$error['md-require-match']).toBeTruthy();
+
+    }));
+
+  });
+
   describe('when required', function() {
     it('properly handles md-min-length="0" and undefined searchText', function() {
       var scope = createScope();

src/components/autocomplete/demoFloatingLabel/index.html

@@ -16,12 +16,14 @@
             md-search-text="ctrl.searchText"
             md-items="item in ctrl.querySearch(ctrl.searchText)"
             md-item-text="item.display"
+            md-require-match=""
             md-floating-label="Favorite state">
           <md-item-template>
             <span md-highlight-text="ctrl.searchText">{{item.display}}</span>
           </md-item-template>
           <div ng-messages="searchForm.autocompleteField.$error" ng-if="searchForm.autocompleteField.$touched">
             <div ng-message="required">You <b>must</b> have a favorite state.</div>
+            <div ng-message="md-require-match">Please select an existing state.</div>
             <div ng-message="minlength">Your entry is not long enough.</div>
             <div ng-message="maxlength">Your entry is too long.</div>
           </div>

src/components/autocomplete/js/autocompleteController.js

@@ -20,7 +20,8 @@ function MdAutocompleteCtrl ($scope, $element, $mdUtil, $mdConstant, $mdTheming,
       hasFocus             = false,
       lastCount            = 0,
       fetchesInProgress    = 0,
-      enableWrapScroll     = null;
+      enableWrapScroll     = null,
+      inputModelCtrl       = null;
 
   //-- public variables with handlers
   defineProperty('hidden', handleHiddenChange, true);
@@ -74,6 +75,12 @@ function MdAutocompleteCtrl ($scope, $element, $mdUtil, $mdConstant, $mdTheming,
     });
   }
 
+  function updateModelValidators() {
+    if (!$scope.requireMatch || !inputModelCtrl) return;
+
+    inputModelCtrl.$setValidity('md-require-match', !!$scope.selectedItem);
+  }
+
   /**
    * Calculates the dropdown's position and applies the new styles to the menu element
    * @returns {*}
@@ -205,9 +212,12 @@ function MdAutocompleteCtrl ($scope, $element, $mdUtil, $mdConstant, $mdTheming,
       wrap:  $element.find('md-autocomplete-wrap')[0],
       root:  document.body
     };
+
     elements.li   = elements.ul.getElementsByTagName('li');
     elements.snap = getSnapTarget();
     elements.$    = getAngularElements(elements);
+
+    inputModelCtrl = elements.$.input.controller('ngModel');
   }
 
   /**
@@ -310,6 +320,9 @@ function MdAutocompleteCtrl ($scope, $element, $mdUtil, $mdConstant, $mdTheming,
    * @param previousSelectedItem
    */
   function selectedItemChange (selectedItem, previousSelectedItem) {
+
+    updateModelValidators();
+
     if (selectedItem) {
       getDisplayValue(selectedItem).then(function (val) {
         $scope.searchText = val;
@@ -372,9 +385,12 @@ function MdAutocompleteCtrl ($scope, $element, $mdUtil, $mdConstant, $mdTheming,
    */
   function handleSearchText (searchText, previousSearchText) {
     ctrl.index = getDefaultIndex();
+
     // do nothing on init
     if (searchText === previousSearchText) return;
 
+    updateModelValidators();
+
     getDisplayValue($scope.selectedItem).then(function (val) {
       // clear selected item if search text no longer matches it
       if (searchText !== val) {

src/components/autocomplete/js/autocompleteDirective.js

@@ -45,6 +45,8 @@ angular
  * @param {string=} placeholder Placeholder text that will be forwarded to the input.
  * @param {boolean=} md-no-cache Disables the internal caching that happens in autocomplete
  * @param {boolean=} ng-disabled Determines whether or not to disable the input field
+ * @param {boolean=} md-require-match When set to true, the autocomplete will add a validator,
+ *     which will evaluate to false, when no item is currently selected.
  * @param {number=} md-min-length Specifies the minimum length of text before autocomplete will
  *     make suggestions
  * @param {number=} md-delay Specifies the amount of time (in milliseconds) to wait before looking
@@ -143,6 +145,7 @@ function MdAutocomplete ($$mdSvgRegistry) {
       itemText:         '&mdItemText',
       placeholder:      '@placeholder',
       noCache:          '=?mdNoCache',
+      requireMatch:     '=?mdRequireMatch',
       selectOnMatch:    '=?mdSelectOnMatch',
       matchInsensitive: '=?mdMatchCaseInsensitive',
       itemChange:       '&?mdSelectedItemChange',