feat(typeahead): handles min-length of 0

Closes #3600

Author: zacronos

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

@@ -842,4 +842,13 @@ describe('typeahead tests', function () {
     expect($scope.select_count).toEqual(1);
   });
 
+  describe('minLength set to 0', function () {
+    it('should open typeahead if input is changed to empty string if defined threshold is 0', function () {
+      var element = prepareInputEl('<div><input ng-model="result" typeahead="item for item in source | filter:$viewValue" typeahead-min-length="0"></div>');
+      changeInputValueTo(element, '');
+
+      expect(element).toBeOpenWithActive(3, 0);
+    });
+  });
+
 });

Diff for: src/typeahead/typeahead.js

@@ -41,7 +41,10 @@ angular.module('ui.bootstrap.typeahead', ['ui.bootstrap.position', 'ui.bootstrap
       //SUPPORTED ATTRIBUTES (OPTIONS)
 
       //minimal no of characters that needs to be entered before typeahead kicks-in
-      var minSearch = originalScope.$eval(attrs.typeaheadMinLength) || 1;
+      var minLength = originalScope.$eval(attrs.typeaheadMinLength);
+      if (!minLength && minLength !== 0) {
+        minLength = 1;
+      }
 
       //minimal wait time after last character typed before typeahead kicks-in
       var waitTime = originalScope.$eval(attrs.typeaheadWaitMs) || 0;
@@ -193,7 +196,7 @@ angular.module('ui.bootstrap.typeahead', ['ui.bootstrap.position', 'ui.bootstrap
 
         hasFocus = true;
 
-        if (inputValue && inputValue.length >= minSearch) {
+        if (minLength === 0 || inputValue && inputValue.length >= minLength) {
           if (waitTime > 0) {
             cancelPreviousTimeout();
             scheduleSearchWithTimeout(inputValue);