feat(input): option to imperatively float placeholder

Refactors the `[floatingPlaceholder]` input to be able to specifiy whether the label should always float or not.

There are three options for the `floatingPlaceholder` input binding now

- If set to `true`, the placeholder will *always* float
- If set to `false`, the placeholder will *never* float
- If set to `null`, the placeholder will float if text is entered.

Closes angular#2466

src/demo-app/input/input-container-demo.html

@@ -180,7 +180,8 @@ <h4>Textarea</h4>
       </md-input-container>
     </p>
     <p>
-      <md-checkbox [(ngModel)]="floatingLabel"> Check to make floating label:</md-checkbox>
+      <md-checkbox [(ngModel)]="floatingLabel">Toggle Floating Label</md-checkbox>
+      <button md-button (click)="floatingLabel = null">Reset Floating Label</button>
       <md-input-container [floatingPlaceholder]="floatingLabel">
         <input mdInput [placeholder]="floatingLabel ? 'Floating label' : 'Not floating label'">
       </md-input-container>

src/lib/input/input-container.html

@@ -7,7 +7,7 @@
 
       <label class="md-input-placeholder"
              [attr.for]="_mdInputChild.id"
-             [class.md-empty]="_mdInputChild.empty"
+             [class.md-empty]="_mdInputChild.empty && !_shouldAlwaysFloat"
              [class.md-focused]="_mdInputChild.focused"
              [class.md-float]="floatingPlaceholder"
              [class.md-accent]="dividerColor == 'accent'"

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

@@ -46,7 +46,8 @@ describe('MdInputContainer', function () {
         MdInputContainerWithValueBinding,
         MdInputContainerWithFormControl,
         MdInputContainerWithStaticPlaceholder,
-        MdInputContainerMissingMdInputTestController
+        MdInputContainerMissingMdInputTestController,
+        MdInputContainerWithDynamicPlaceholder
       ],
     });
 
@@ -404,6 +405,78 @@ describe('MdInputContainer', function () {
     const textarea: HTMLTextAreaElement = fixture.nativeElement.querySelector('textarea');
     expect(textarea).not.toBeNull();
   });
+
+  it('should float when floatingPlaceholder is set to default and text is entered', () => {
+    let fixture = TestBed.createComponent(MdInputContainerWithDynamicPlaceholder);
+    fixture.detectChanges();
+
+    let inputEl = fixture.debugElement.query(By.css('input'));
+    let labelEl = fixture.debugElement.query(By.css('label')).nativeElement;
+
+    expect(labelEl.classList).not.toContain('md-empty');
+    expect(labelEl.classList).toContain('md-float');
+
+    fixture.componentInstance.shouldFloat = null;
+    fixture.detectChanges();
+
+    expect(labelEl.classList).toContain('md-empty');
+    expect(labelEl.classList).toContain('md-float');
+
+    // Update the value of the input.
+    inputEl.nativeElement.value = 'Text';
+
+    // Fake behavior of the `(input)` event which should trigger a change detection.
+    fixture.detectChanges();
+
+    expect(labelEl.classList).not.toContain('md-empty');
+    expect(labelEl.classList).toContain('md-float');
+  });
+
+  it('should always float the placeholder when floatingPlaceholder is set to true', () => {
+    let fixture = TestBed.createComponent(MdInputContainerWithDynamicPlaceholder);
+    fixture.detectChanges();
+
+    let inputEl = fixture.debugElement.query(By.css('input'));
+    let labelEl = fixture.debugElement.query(By.css('label')).nativeElement;
+
+    expect(labelEl.classList).not.toContain('md-empty');
+    expect(labelEl.classList).toContain('md-float');
+
+    fixture.detectChanges();
+
+    // Update the value of the input.
+    inputEl.nativeElement.value = 'Text';
+
+    // Fake behavior of the `(input)` event which should trigger a change detection.
+    fixture.detectChanges();
+
+    expect(labelEl.classList).not.toContain('md-empty');
+    expect(labelEl.classList).toContain('md-float');
+  });
+
+
+  it('should never float the placeholder when floatingPlaceholder is set to false', () => {
+    let fixture = TestBed.createComponent(MdInputContainerWithDynamicPlaceholder);
+
+    fixture.componentInstance.shouldFloat = false;
+    fixture.detectChanges();
+
+    let inputEl = fixture.debugElement.query(By.css('input'));
+    let labelEl = fixture.debugElement.query(By.css('label')).nativeElement;
+
+    expect(labelEl.classList).toContain('md-empty');
+    expect(labelEl.classList).not.toContain('md-float');
+
+    // Update the value of the input.
+    inputEl.nativeElement.value = 'Text';
+
+    // Fake behavior of the `(input)` event which should trigger a change detection.
+    fixture.detectChanges();
+
+    expect(labelEl.classList).not.toContain('md-empty');
+    expect(labelEl.classList).not.toContain('md-float');
+  });
+
 });
 
 @Component({
@@ -580,6 +653,16 @@ class MdInputContainerWithValueBinding {
 })
 class MdInputContainerWithStaticPlaceholder {}
 
+@Component({
+  template: `
+    <md-input-container [floatingPlaceholder]="shouldFloat">
+      <input md-input placeholder="Label">
+    </md-input-container>`
+})
+class MdInputContainerWithDynamicPlaceholder {
+  shouldFloat: boolean = true;
+}
+
 @Component({
   template: `
     <md-input-container>

src/lib/input/input-container.ts

@@ -248,6 +248,13 @@ export class MdInputContainer implements AfterContentInit {
   /** Color of the input divider, based on the theme. */
   @Input() dividerColor: 'primary' | 'accent' | 'warn' = 'primary';
 
+  /** Whether the floating label should always float or not. */
+  _shouldAlwaysFloat: boolean = false;
+
+  /** Whether the placeholder can float or not. */
+  _floatingPlaceholder: boolean = true;
+
+
   /** Text for the input hint. */
   @Input()
   get hintLabel() { return this._hintLabel; }
@@ -257,11 +264,16 @@ export class MdInputContainer implements AfterContentInit {
   }
   private _hintLabel = '';
 
-  /** Text or the floating placeholder. */
+  /**
+   * Whether the placeholder should always float or just show the placeholder when empty.
+   * If the value is set to null the placeholder will float if text is entered.
+   */
   @Input()
-  get floatingPlaceholder(): boolean { return this._floatingPlaceholder; }
-  set floatingPlaceholder(value) { this._floatingPlaceholder = coerceBooleanProperty(value); }
-  private _floatingPlaceholder: boolean = true;
+  get floatingPlaceholder() { return this._floatingPlaceholder; }
+  set floatingPlaceholder(value: boolean) {
+    this._floatingPlaceholder = value == null || coerceBooleanProperty(value);
+    this._shouldAlwaysFloat = coerceBooleanProperty(value);
+  }
 
   @ContentChild(MdInputDirective) _mdInputChild: MdInputDirective;