fix(input): treat number 0 as non-empty (#2245)

src/lib/input/input-container.spec.ts

@@ -38,6 +38,7 @@ describe('MdInputContainer', function () {
         MdInputContainerTextTestController,
         MdInputContainerPasswordTestController,
         MdInputContainerNumberTestController,
+        MdInputContainerZeroTestController,
         MdTextareaWithBindings,
         MdInputContainerWithDisabled,
         MdInputContainerMissingMdInputTestController
@@ -127,6 +128,19 @@ describe('MdInputContainer', function () {
     expect(el.classList.contains('md-empty')).toBe(false, 'should not be empty');
   }));
 
+  it('should not treat the number 0 as empty', async(() => {
+    let fixture = TestBed.createComponent(MdInputContainerZeroTestController);
+    fixture.detectChanges();
+
+    fixture.whenStable().then(() => {
+      fixture.detectChanges();
+
+      let el = fixture.debugElement.query(By.css('label')).nativeElement;
+      expect(el).not.toBeNull();
+      expect(el.classList.contains('md-empty')).toBe(false);
+    });
+  }));
+
   it('should add id', () => {
     let fixture = TestBed.createComponent(MdInputContainerTextTestController);
     fixture.detectChanges();
@@ -405,6 +419,16 @@ class MdInputContainerPasswordTestController {}
 })
 class MdInputContainerNumberTestController {}
 
+@Component({
+  template: `
+    <md-input-container>
+      <input md-input type="number" placeholder="Placeholder" [(ngModel)]="value">
+    </md-input-container>`
+})
+class MdInputContainerZeroTestController {
+  value = 0;
+}
+
 @Component({
   template: `
     <md-input-container>

src/lib/input/input-container.ts

@@ -118,7 +118,7 @@ export class MdInputDirective implements AfterContentInit {
    */
   @Output() _placeholderChange = new EventEmitter<string>();
 
-  get empty() { return (this.value == null || this.value == '') && !this._isNeverEmpty(); }
+  get empty() { return (this.value == null || this.value === '') && !this._isNeverEmpty(); }
 
   focused = false;