feat(form-field): add support for separate label and placeholder

* Adds the ability for the user to specify both a label and placeholder text for a form field.
* Renames all of the "floating placeholder" related terminology to refer to a "floating label" instead.
* Aligns the input placeholder color with the Material spec.

BREAKING CHANGE: The `MatFormFieldControl.shouldPlaceholderFloat` property has been renamed to `shouldLabelFloat`.
BREAKING CHANGE: The `MAT_PLACEHOLDER_GLOBAL_OPTIONS`, `FloatPlaceholderType` and `PlaceholderOptions` symbols are now deprecated. Use `MAT_LABEL_GLOBAL_OPTIONS`, `FloatLabelType` and `LabelOptions` instead.
BREAKING CHANGE: The `MatFormField.floatPlaceholder` input has been deprecated, use `floatLabel` instead.

Fixes #6194.

Author: crisbeto

.github/CODEOWNERS

@@ -41,6 +41,7 @@
 /src/lib/core/line/**                              @jelbourn
 /src/lib/core/option/**                            @kara @crisbeto
 /src/lib/core/placeholder/**                       @kara @mmalerba
+/src/lib/core/label/**                             @kara @mmalerba
 /src/lib/core/ripple/**                            @devversion
 /src/lib/core/selection/**                         @tinayuangao @jelbourn
 /src/lib/core/selection/pseudo*/**                 @crisbeto @jelbourn

guides/creating-a-custom-form-field-control.md

@@ -58,7 +58,7 @@ class MyTelInput {
     tel = tel || new MyTel('', '', '');
     this.parts.setValue({area: tel.area, exchange: tel.exchange, subscriber: tel.subscriber});
   }
-  
+
   constructor(fb: FormBuilder) {
     this.parts =  fb.group({
       'area': '',
@@ -98,7 +98,7 @@ the `MatFormFieldControl` interface, see the
 #### `value`
 
 This property allows someone to set or get the value of our control. Its type should be the same
-type we used for the type parameter when we implemented `MatFormFieldControl`. Since our component 
+type we used for the type parameter when we implemented `MatFormFieldControl`. Since our component
 already has a value property, we don't need to do anything for this one.
 
 #### `stateChanges`
@@ -212,16 +212,16 @@ get empty() {
 }
 ```
 
-#### `shouldPlaceholderFloat`
+#### `shouldLabelFloat`
 
-This property is used to indicate whether the placeholder should be in the floating position. We'll
+This property is used to indicate whether the label should be in the floating position. We'll
 use the same logic as `matInput` and float the placeholder when the input is focused or non-empty.
 Since the placeholder will be overlapping our control when when it's not floating, we should hide
 the `–` characters when it's not floating.
 
 ```ts
 @HostBinding('class.floating')
-get shouldPlaceholderFloat() {
+get shouldLabelFloat() {
   return this.focused || !this.empty;
 }
 ```
@@ -307,7 +307,7 @@ just need to apply the given IDs to our host element.
 
 ```ts
 @HostBinding('attr.aria-describedby') describedBy = '';
-  
+
 setDescribedByIds(ids: string[]) {
   this.describedBy = ids.join(' ');
 }

src/demo-app/a11y/input/input-a11y.html

@@ -1,9 +1,9 @@
 <section>
   <h2>Basic input box (e.g. name field)</h2>
-  <mat-form-field floatPlaceholder="never">
+  <mat-form-field floatLabel="never">
     <input matInput placeholder="First name" [(ngModel)]="firstName">
   </mat-form-field>
-  <mat-form-field floatPlaceholder="never">
+  <mat-form-field floatLabel="never">
     <input matInput placeholder="Last name" [(ngModel)]="lastName">
   </mat-form-field>
 </section>
@@ -34,12 +34,12 @@ <h2>Input with error message (e.g. email field)</h2>
 
 <section>
   <h2>Input with prefix & suffix (e.g. currency converter)</h2>
-  <mat-form-field floatPlaceholder="always">
+  <mat-form-field floatLabel="always">
     <input matInput type="number" placeholder="USD" [(ngModel)]="usd">
     <span matPrefix>$</span>
   </mat-form-field>
   =
-  <mat-form-field floatPlaceholder="always">
+  <mat-form-field floatLabel="always">
     <input matInput type="number" placeholder="JPY" [(ngModel)]="jpy">
     <span matPrefix>‎¥‎</span>
   </mat-form-field>

src/demo-app/autocomplete/autocomplete-demo.html

@@ -6,7 +6,7 @@
     <div>Reactive value: {{ stateCtrl.value | json }}</div>
     <div>Reactive dirty: {{ stateCtrl.dirty }}</div>
 
-    <mat-form-field floatPlaceholder="never">
+    <mat-form-field floatLabel="never">
       <input matInput placeholder="State" [matAutocomplete]="reactiveAuto" [formControl]="stateCtrl">
       <mat-autocomplete #reactiveAuto="matAutocomplete" [displayWith]="displayFn">
         <mat-option *ngFor="let state of reactiveStates | async" [value]="state">

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

@@ -384,12 +384,115 @@ <h4>Textarea</h4>
     </button>
     <div>
       <mat-form-field>
-          <input matInput placeholder="delayed value" [formControl]="delayedFormControl">
+        <input matInput placeholder="delayed value" [formControl]="delayedFormControl">
       </mat-form-field>
     </div>
   </mat-card-content>
 </mat-card>
 
+
+<mat-card class="demo-card demo-basic">
+  <mat-toolbar color="primary">Floating labels</mat-toolbar>
+
+  <mat-card-content>
+    <div>
+      <mat-form-field>
+        <input matInput [formControl]="placeholderTestControl">
+      </mat-form-field>
+
+      <mat-form-field>
+        <input matInput [formControl]="placeholderTestControl" placeholder="Only placeholder">
+      </mat-form-field>
+
+      <mat-form-field>
+        <mat-label>Only label</mat-label>
+        <input matInput [formControl]="placeholderTestControl">
+      </mat-form-field>
+
+      <mat-form-field>
+        <mat-label>Label and placeholder</mat-label>
+        <input matInput [formControl]="placeholderTestControl" placeholder="This is the placeholder">
+      </mat-form-field>
+
+      <mat-form-field floatLabel="always">
+        <mat-label>Always float</mat-label>
+        <input matInput [formControl]="placeholderTestControl" placeholder="This is the placeholder">
+      </mat-form-field>
+
+      <mat-form-field floatLabel="never">
+        <mat-label>Never float</mat-label>
+        <input matInput [formControl]="placeholderTestControl" placeholder="This is the placeholder">
+      </mat-form-field>
+
+      <mat-form-field>
+        <mat-label>Label and placeholder element</mat-label>
+        <mat-placeholder>The placeholder element</mat-placeholder>
+        <input matInput [formControl]="placeholderTestControl">
+      </mat-form-field>
+    </div>
+
+    <div>
+      <mat-form-field>
+        <mat-select [formControl]="placeholderTestControl">
+          <mat-option value="Value">Value</mat-option>
+        </mat-select>
+      </mat-form-field>
+
+      <mat-form-field>
+        <mat-select [formControl]="placeholderTestControl" placeholder="Only placeholder">
+          <mat-option value="Value">Value</mat-option>
+        </mat-select>
+      </mat-form-field>
+
+      <mat-form-field>
+        <mat-label>Only label</mat-label>
+        <mat-select [formControl]="placeholderTestControl">
+          <mat-option value="Value">Value</mat-option>
+        </mat-select>
+      </mat-form-field>
+
+      <mat-form-field>
+        <mat-label>Label and placeholder</mat-label>
+        <mat-select [formControl]="placeholderTestControl" placeholder="This is the placeholder">
+          <mat-option value="Value">Value</mat-option>
+        </mat-select>
+      </mat-form-field>
+
+      <mat-form-field floatLabel="always">
+        <mat-label>Always float</mat-label>
+        <mat-select [formControl]="placeholderTestControl" placeholder="This is the placeholder">
+          <mat-option value="Value">Value</mat-option>
+        </mat-select>
+      </mat-form-field>
+
+      <mat-form-field floatLabel="never">
+        <mat-label>Never float</mat-label>
+        <mat-select [formControl]="placeholderTestControl" placeholder="This is the placeholder">
+          <mat-option value="Value">Value</mat-option>
+        </mat-select>
+      </mat-form-field>
+
+      <mat-form-field>
+        <mat-label>Label and placeholder element</mat-label>
+        <mat-placeholder>The placeholder element</mat-placeholder>
+        <mat-select [formControl]="placeholderTestControl">
+          <mat-option value="Value">Value</mat-option>
+        </mat-select>
+      </mat-form-field>
+    </div>
+
+    <button
+      mat-raised-button
+      color="primary"
+      (click)="togglePlaceholderTestValue()">Toggle value</button>
+
+    <button
+      mat-raised-button
+      color="primary"
+      (click)="togglePlaceholderTestTouched()">Toggle touched</button>
+  </mat-card-content>
+</mat-card>
+
 <mat-card class="demo-card demo-basic">
   <mat-toolbar color="primary">Textarea Autosize</mat-toolbar>
   <mat-card-content>

src/demo-app/input/input-demo.ts

@@ -21,6 +21,7 @@ export class InputDemo {
   hideRequiredMarker: boolean;
   ctrlDisabled = false;
   textareaNgModelValue: string;
+  placeholderTestControl = new FormControl('', Validators.required);
 
   name: string;
   errorMessageExample1: string;
@@ -65,4 +66,14 @@ export class InputDemo {
       return false;
     }
   };
+
+  togglePlaceholderTestValue() {
+    this.placeholderTestControl.setValue(this.placeholderTestControl.value === '' ? 'Value' : '');
+  }
+
+  togglePlaceholderTestTouched() {
+    this.placeholderTestControl.touched ?
+      this.placeholderTestControl.markAsUntouched() :
+      this.placeholderTestControl.markAsTouched();
+  }
 }

src/demo-app/select/select-demo.html

@@ -6,7 +6,7 @@
   <mat-card>
     <mat-card-subtitle>ngModel</mat-card-subtitle>
 
-    <mat-form-field [floatPlaceholder]="floatPlaceholder" [color]="drinksTheme">
+    <mat-form-field [floatLabel]="floatLabel" [color]="drinksTheme">
       <mat-select placeholder="Drink" [(ngModel)]="currentDrink" [required]="drinksRequired"
         [disabled]="drinksDisabled" #drinkControl="ngModel">
         <mat-option>None</mat-option>
@@ -24,7 +24,7 @@
     <p> Status: {{ drinkControl.control?.status }} </p>
     <p>
       <label for="floating-placeholder">Floating placeholder:</label>
-      <select [(ngModel)]="floatPlaceholder" id="floating-placeholder">
+      <select [(ngModel)]="floatLabel" id="floating-placeholder">
         <option value="auto">Auto</option>
         <option value="always">Always</option>
         <option value="never">Never</option>

src/demo-app/select/select-demo.ts

@@ -21,7 +21,7 @@ export class SelectDemo {
   currentPokemonFromGroup: string;
   currentDigimon: string;
   latestChangeEvent: MatSelectChange;
-  floatPlaceholder: string = 'auto';
+  floatLabel: string = 'auto';
   foodControl = new FormControl('pizza-1');
   topHeightCtrl = new FormControl(0);
   drinksTheme = 'primary';

src/lib/autocomplete/autocomplete-trigger.ts

@@ -123,8 +123,8 @@ export class MatAutocompleteTrigger implements ControlValueAccessor, OnDestroy {
   /** Strategy that is used to position the panel. */
   private _positionStrategy: ConnectedPositionStrategy;
 
-  /** Whether or not the placeholder state is being overridden. */
-  private _manuallyFloatingPlaceholder = false;
+  /** Whether or not the label state is being overridden. */
+  private _manuallyFloatingLabel = false;
 
   /** The subscription for closing actions (some are bound to document). */
   private _closingActionsSubscription: Subscription;
@@ -163,7 +163,7 @@ export class MatAutocompleteTrigger implements ControlValueAccessor, OnDestroy {
   /** Opens the autocomplete suggestion panel. */
   openPanel(): void {
     this._attachOverlay();
-    this._floatPlaceholder();
+    this._floatLabel();
   }
 
   /** Closes the autocomplete suggestion panel. */
@@ -173,14 +173,14 @@ export class MatAutocompleteTrigger implements ControlValueAccessor, OnDestroy {
       this._closingActionsSubscription.unsubscribe();
     }
 
-    this._resetPlaceholder();
+    this._resetLabel();
 
     if (this._panelOpen) {
       this.autocomplete._isOpen = this._panelOpen = false;
 
       // We need to trigger change detection manually, because
       // `fromEvent` doesn't seem to do it at the proper time.
-      // This ensures that the placeholder is reset when the
+      // This ensures that the label is reset when the
       // user clicks outside.
       this._changeDetectorRef.detectChanges();
     }
@@ -307,33 +307,33 @@ export class MatAutocompleteTrigger implements ControlValueAccessor, OnDestroy {
   _handleFocus(): void {
     if (!this._element.nativeElement.readOnly) {
       this._attachOverlay();
-      this._floatPlaceholder(true);
+      this._floatLabel(true);
     }
   }
 
   /**
-   * In "auto" mode, the placeholder will animate down as soon as focus is lost.
+   * In "auto" mode, the label will animate down as soon as focus is lost.
    * This causes the value to jump when selecting an option with the mouse.
-   * This method manually floats the placeholder until the panel can be closed.
-   * @param shouldAnimate Whether the placeholder should be animated when it is floated.
+   * This method manually floats the label until the panel can be closed.
+   * @param shouldAnimate Whether the label should be animated when it is floated.
    */
-  private _floatPlaceholder(shouldAnimate = false): void {
-    if (this._formField && this._formField.floatPlaceholder === 'auto') {
+  private _floatLabel(shouldAnimate = false): void {
+    if (this._formField && this._formField.floatLabel === 'auto') {
       if (shouldAnimate) {
-        this._formField._animateAndLockPlaceholder();
+        this._formField._animateAndLockLabel();
       } else {
-        this._formField.floatPlaceholder = 'always';
+        this._formField.floatLabel = 'always';
       }
 
-      this._manuallyFloatingPlaceholder = true;
+      this._manuallyFloatingLabel = true;
     }
   }
 
-  /** If the placeholder has been manually elevated, return it to its normal state. */
-  private _resetPlaceholder(): void  {
-    if (this._manuallyFloatingPlaceholder) {
-      this._formField.floatPlaceholder = 'auto';
-      this._manuallyFloatingPlaceholder = false;
+  /** If the label has been manually elevated, return it to its normal state. */
+  private _resetLabel(): void  {
+    if (this._manuallyFloatingLabel) {
+      this._formField.floatLabel = 'auto';
+      this._manuallyFloatingLabel = false;
     }
   }