fix(input): `false` is no longer an empty value by default

`checkboxInputType` and `ngList` directives need to have special logic for whether
they are empty or not.  Previously this had been hard coded into their
own directives or the `ngRequired` directive.  This made it difficult to handle
these special cases.

This change factors out the question of whether an input is empty into a method
`$isEmpty` on the `ngModelController`.  The `ngRequired` directive now uses this
method when testing for validity and directives, such as `checkbox` or `ngList`
can override it to apply logic specific to their needs.

Closes #3490, #3658, #2594

1 files changed, 25 insertions, 0 deletions

diff --git a/test/ng/directive/selectSpec.js b/test/ng/directive/selectSpec.js
index 85acba19..ac0cc70d 100644
--- a/test/ng/directive/selectSpec.js
+++ b/test/ng/directive/selectSpec.js
@@ -1213,6 +1213,31 @@ describe('select', function() {
         });
         expect(element).toBeValid();
       });
+
+
+      it('should allow falsy values as values', function() {
+        createSelect({
+          'ng-model': 'value',
+          'ng-options': 'item.value as item.name for item in values',
+          'ng-required': 'required'
+        }, true);
+
+        scope.$apply(function() {
+          scope.values = [{name: 'True', value: true}, {name: 'False', value: false}];
+          scope.required = false;
+        });
+
+        element.val('1');
+        browserTrigger(element, 'change');
+        expect(element).toBeValid();
+        expect(scope.value).toBe(false);
+
+        scope.$apply(function() {
+          scope.required = true;
+        });
+        expect(element).toBeValid();
+        expect(scope.value).toBe(false);
+      });
     });
   });