feat(select): add multiple selection mode

* Integrates the `SelectionModel` into `md-select`.
* Adds the `multiple` option which allows users to select multiple options from a `md-select`.
* Fixes a button that wasn't being cleaned up from dialog tests, causing some select tests to fail.

Fixes angular#2412.

Author: crisbeto

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

@@ -1,45 +1,78 @@
 <div style="height: 1000px">This div is for testing scrolled selects.</div>
 <button md-button (click)="showSelect=!showSelect">SHOW SELECT</button>
 <div class="demo-select">
-  <div *ngIf="showSelect">
-    <md-card>
-      <md-select placeholder="Food i would like to eat" [formControl]="foodControl">
-        <md-option *ngFor="let food of foods" [value]="food.value"> {{ food.viewValue }} </md-option>
+  <md-card>
+    <md-card-subtitle>ngModel</md-card-subtitle>
+
+    <md-card-content>
+      <md-select placeholder="Drink" [(ngModel)]="currentDrink" [required]="drinksRequired"
+        [disabled]="drinksDisabled" #drinkControl="ngModel">
+        <md-option *ngFor="let drink of drinks" [value]="drink.value" [disabled]="drink.disabled">
+          {{ drink.viewValue }}
+        </md-option>
       </md-select>
-      <p> Value: {{ foodControl.value }} </p>
-      <p> Touched: {{ foodControl.touched }} </p>
-      <p> Dirty: {{ foodControl.dirty }} </p>
-      <p> Status: {{ foodControl.status }} </p>
-      <button md-button (click)="foodControl.setValue('pizza-1')">SET VALUE</button>
-      <button md-button (click)="toggleDisabled()">TOGGLE DISABLED</button>
-      <button md-button (click)="foodControl.reset()">RESET</button>
-    </md-card>
-  </div>
+      <p> Value: {{ currentDrink }} </p>
+      <p> Touched: {{ drinkControl.touched }} </p>
+      <p> Dirty: {{ drinkControl.dirty }} </p>
+      <p> Status: {{ drinkControl.control?.status }} </p>
+      <button md-button (click)="currentDrink='sprite-1'">SET VALUE</button>
+      <button md-button (click)="drinksRequired=!drinksRequired">TOGGLE REQUIRED</button>
+      <button md-button (click)="drinksDisabled=!drinksDisabled">TOGGLE DISABLED</button>
+      <button md-button (click)="drinkControl.reset()">RESET</button>
+    </md-card-content>
+  </md-card>
 
   <md-card>
-    <md-select placeholder="Drink" [(ngModel)]="currentDrink" [required]="isRequired" [disabled]="isDisabled"
-      #drinkControl="ngModel">
-      <md-option *ngFor="let drink of drinks" [value]="drink.value" [disabled]="drink.disabled">
-        {{ drink.viewValue }}
-      </md-option>
-    </md-select>
-    <p> Value: {{ currentDrink }} </p>
-    <p> Touched: {{ drinkControl.touched }} </p>
-    <p> Dirty: {{ drinkControl.dirty }} </p>
-    <p> Status: {{ drinkControl.control?.status }} </p>
-    <button md-button (click)="currentDrink='sprite-1'">SET VALUE</button>
-    <button md-button (click)="isRequired=!isRequired">TOGGLE REQUIRED</button>
-    <button md-button (click)="isDisabled=!isDisabled">TOGGLE DISABLED</button>
-    <button md-button (click)="drinkControl.reset()">RESET</button>
+    <md-card-subtitle>Multiple selection</md-card-subtitle>
+
+    <md-card-content>
+      <md-select multiple placeholder="Pokemon" [(ngModel)]="currentPokemon"
+        [required]="pokemonRequired" [disabled]="pokemonDisabled" #pokemonControl="ngModel">
+        <md-option *ngFor="let creature of pokemon" [value]="creature.value">
+          {{ creature.viewValue }}
+        </md-option>
+      </md-select>
+      <p> Value: {{ currentPokemon }} </p>
+      <p> Touched: {{ pokemonControl.touched }} </p>
+      <p> Dirty: {{ pokemonControl.dirty }} </p>
+      <p> Status: {{ pokemonControl.control?.status }} </p>
+      <button md-button (click)="currentPokemon=['eevee-4', 'psyduck-6']">SET VALUE</button>
+      <button md-button (click)="pokemonRequired=!pokemonRequired">TOGGLE REQUIRED</button>
+      <button md-button (click)="pokemonDisabled=!pokemonDisabled">TOGGLE DISABLED</button>
+      <button md-button (click)="pokemonControl.reset()">RESET</button>
+    </md-card-content>
   </md-card>
 
   <div *ngIf="showSelect">
     <md-card>
-      <md-select placeholder="Starter Pokemon" (change)="latestChangeEvent = $event">
-        <md-option *ngFor="let starter of pokemon" [value]="starter.value"> {{ starter.viewValue }} </md-option>
-      </md-select>
+      <md-card-subtitle>formControl</md-card-subtitle>
+
+      <md-card-content>
+        <md-select placeholder="Food i would like to eat" [formControl]="foodControl">
+          <md-option *ngFor="let food of foods" [value]="food.value"> {{ food.viewValue }}</md-option>
+        </md-select>
+        <p> Value: {{ foodControl.value }} </p>
+        <p> Touched: {{ foodControl.touched }} </p>
+        <p> Dirty: {{ foodControl.dirty }} </p>
+        <p> Status: {{ foodControl.status }} </p>
+        <button md-button (click)="foodControl.setValue('pizza-1')">SET VALUE</button>
+        <button md-button (click)="toggleDisabled()">TOGGLE DISABLED</button>
+        <button md-button (click)="foodControl.reset()">RESET</button>
+      </md-card-content>
+    </md-card>
+  </div>
+
+  <div *ngIf="showSelect">
+    <md-card>
+      <md-card-subtitle>Change event</md-card-subtitle>
+
+      <md-card-content>
+        <md-select placeholder="Starter Pokemon" (change)="latestChangeEvent = $event">
+          <md-option *ngFor="let creature of pokemon" [value]="creature.value">{{ creature.viewValue }}</md-option>
+        </md-select>
 
-      <p> Change event value: {{ latestChangeEvent?.value }} </p>
+        <p> Change event value: {{ latestChangeEvent?.value }} </p>
+      </md-card-content>
     </md-card>
   </div>
 

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

@@ -9,10 +9,13 @@ import {MdSelectChange} from '@angular/material';
     styleUrls: ['select-demo.css'],
 })
 export class SelectDemo {
-  isRequired = false;
-  isDisabled = false;
+  drinksRequired = false;
+  pokemonRequired = false;
+  drinksDisabled = false;
+  pokemonDisabled = false;
   showSelect = false;
   currentDrink: string;
+  currentPokemon: string[];
   latestChangeEvent: MdSelectChange;
   foodControl = new FormControl('pizza-1');
 
@@ -37,7 +40,11 @@ export class SelectDemo {
   pokemon = [
     {value: 'bulbasaur-0', viewValue: 'Bulbasaur'},
     {value: 'charizard-1', viewValue: 'Charizard'},
-    {value: 'squirtle-2', viewValue: 'Squirtle'}
+    {value: 'squirtle-2', viewValue: 'Squirtle'},
+    {value: 'pikachu-3', viewValue: 'Pikachu'},
+    {value: 'eevee-4', viewValue: 'Eevee'},
+    {value: 'ditto-5', viewValue: 'Ditto'},
+    {value: 'psyduck-6', viewValue: 'Psyduck'},
   ];
 
   toggleDisabled() {

src/lib/autocomplete/autocomplete-trigger.ts

@@ -72,7 +72,7 @@ export class MdAutocompleteTrigger implements OnDestroy {
 
   /** Stream of autocomplete option selections. */
   get optionSelections(): Observable<any>[] {
-    return this.autocomplete.options.map(option => option.onSelect);
+    return this.autocomplete.options.map(option => option.onToggle);
   }
 
   /** Destroys the autocomplete suggestion panel. */

src/lib/core/option/option.ts

@@ -20,6 +20,10 @@ import {MdRippleModule} from '../ripple/ripple';
  */
 let _uniqueIdCounter = 0;
 
+export class MdOptionToggle {
+  constructor(public source: MdOption, public isUserInput = false) { }
+}
+
 /**
  * Single option inside of a `<md-select>` element.
  */
@@ -48,9 +52,15 @@ export class MdOption {
 
   private _id: string = `md-option-${_uniqueIdCounter++}`;
 
+  /** Whether the wrapping component is in multiple selection mode. */
+  multiple: boolean = false;
+
   /** The unique ID of the option. */
   get id() { return this._id; }
 
+  /** Whether or not the option is currently selected. */
+  get selected(): boolean { return this._selected; }
+
   /** The form value of the option. */
   @Input() value: any;
 
@@ -59,16 +69,11 @@ export class MdOption {
   get disabled() { return this._disabled; }
   set disabled(value: any) { this._disabled = coerceBooleanProperty(value); }
 
-  /** Event emitted when the option is selected. */
-  @Output() onSelect = new EventEmitter();
+  /** Event emitted when the option is selected or deselected. */
+  @Output() onToggle = new EventEmitter<MdOptionToggle>();
 
   constructor(private _element: ElementRef, private _renderer: Renderer) {}
 
-  /** Whether or not the option is currently selected. */
-  get selected(): boolean {
-    return this._selected;
-  }
-
   /**
    * The displayed value of the option. It is necessary to show the selected option in the
    * select's trigger.
@@ -81,12 +86,13 @@ export class MdOption {
   /** Selects the option. */
   select(): void {
     this._selected = true;
-    this.onSelect.emit();
+    this._emitToggleEvent();
   }
 
   /** Deselects the option. */
   deselect(): void {
     this._selected = false;
+    this._emitToggleEvent();
   }
 
   /** Sets focus onto this option. */
@@ -107,8 +113,8 @@ export class MdOption {
    */
   _selectViaInteraction() {
     if (!this.disabled) {
-      this._selected = true;
-      this.onSelect.emit(true);
+      this._selected = this.multiple ? !this._selected : true;
+      this._emitToggleEvent(true);
     }
   }
 
@@ -117,10 +123,16 @@ export class MdOption {
     return this.disabled ? '-1' : '0';
   }
 
+  /** Fetches the host DOM element. */
   _getHostElement(): HTMLElement {
     return this._element.nativeElement;
   }
 
+  /** Emits the toggle event. */
+  private _emitToggleEvent(isUserInput?: boolean) {
+    this.onToggle.emit(new MdOptionToggle(this, isUserInput));
+  };
+
 }
 
 @NgModule({

src/lib/core/selection/selection.spec.ts

@@ -156,6 +156,16 @@ describe('SelectionModel', () => {
     expect(model.isEmpty()).toBe(false);
   });
 
+  it('should be able to toggle an option', () => {
+    let model = new SelectionModel();
+
+    model.toggle(1);
+    expect(model.isSelected(1)).toBe(true);
+
+    model.toggle(1);
+    expect(model.isSelected(1)).toBe(false);
+  });
+
   it('should be able to clear the selected options', () => {
     let model = new SelectionModel(true);
 

src/lib/core/selection/selection.ts

@@ -59,6 +59,17 @@ export class SelectionModel<T> {
     this._emitChangeEvent();
   }
 
+  /**
+   * Toggles a value between selected and deselected.
+   */
+  toggle(value: T): void {
+    if (this.isSelected(value)) {
+      this.deselect(value);
+    } else {
+      this.select(value);
+    }
+  }
+
   /**
    * Clears all of the selected values.
    */

src/lib/dialog/dialog.spec.ts

@@ -307,6 +307,8 @@ describe('MdDialog', () => {
 
       expect(document.activeElement.id)
           .toBe('dialog-trigger', 'Expected that the trigger was refocused after dialog close');
+
+      document.body.removeChild(button);
     }));
   });
 

src/lib/select/select-errors.ts

@@ -0,0 +1,21 @@
+import {MdError} from '../core/errors/error';
+
+/**
+ * Exception thrown when attempting to change a select's `multiple` option after initialization.
+ * @docs-private
+ */
+export class MdSelectDynamicMultipleError extends MdError {
+  constructor() {
+    super('Cannot change `multiple` mode of select after initialization.');
+  }
+}
+
+/**
+ * Exception thrown when attempting to assign a non-array value to a select in `multiple` mode.
+ * @docs-private
+ */
+export class MdSelectNonArrayValueError extends MdError {
+  constructor() {
+    super('Cannot assign non-array value to select in `multiple` mode.');
+  }
+}

src/lib/select/select.html

@@ -1,7 +1,7 @@
 <div class="md-select-trigger" cdk-overlay-origin (click)="toggle()" #origin="cdkOverlayOrigin" #trigger>
-  <span class="md-select-placeholder" [class.md-floating-placeholder]="this.selected"
+  <span class="md-select-placeholder" [class.md-floating-placeholder]="!_model.isEmpty()"
    [@transformPlaceholder]="_placeholderState" [style.width.px]="_selectedValueWidth"> {{ placeholder }} </span>
-  <span class="md-select-value" *ngIf="selected"> {{ selected?.viewValue }} </span>
+  <span class="md-select-value" *ngIf="!_model.isEmpty()"> {{ selectedLabel }} </span>
   <span class="md-select-arrow"></span>
 </div>