fix(select): don't shift option focus when multi-select value is changed programmatically (#5401)

Doesn't shift focus when the value of a multi select is updated programmatically while the panel is still open. Previously focus would end up on the last selected option, because we move focus in a loop.

Fixes #5381.

src/lib/select/select.spec.ts

@@ -1838,6 +1838,31 @@ describe('MdSelect', () => {
         expect(fixture.componentInstance.options.toArray()[6].selected).toBe(true);
       });
 
+      it('should not shift focus when the selected options are updated programmatically ' +
+        'in a multi select', () => {
+          fixture.destroy();
+
+          const multiFixture = TestBed.createComponent(MultiSelect);
+          const instance = multiFixture.componentInstance;
+
+          multiFixture.detectChanges();
+          select = multiFixture.debugElement.query(By.css('md-select')).nativeElement;
+          multiFixture.componentInstance.select.open();
+          multiFixture.detectChanges();
+
+          const options =
+              overlayContainerElement.querySelectorAll('md-option') as NodeListOf<HTMLElement>;
+
+          options[3].focus();
+          expect(document.activeElement).toBe(options[3], 'Expected fourth option to be focused.');
+
+          multiFixture.componentInstance.control.setValue(['steak-0', 'sushi-7']);
+          multiFixture.detectChanges();
+
+          expect(document.activeElement)
+              .toBe(options[3], 'Expected fourth option to remain focused.');
+        });
+
       it('should not cycle through the options if the control is disabled', () => {
         const formControl = fixture.componentInstance.control;
 

src/lib/select/select.ts

@@ -687,7 +687,13 @@ export class MdSelect extends _MdSelectMixinBase implements AfterContentInit, On
       value.forEach((currentValue: any) => this._selectValue(currentValue, isUserInput));
       this._sortValues();
     } else {
-      this._selectValue(value, isUserInput);
+      const correspondingOption = this._selectValue(value, isUserInput);
+
+      // Shift focus to the active item. Note that we shouldn't do this in multiple
+      // mode, because we don't know what option the user interacted with last.
+      if (correspondingOption) {
+        this._keyManager.setActiveItem(this.options.toArray().indexOf(correspondingOption));
+      }
     }
 
     this._setValueWidth();
@@ -704,15 +710,13 @@ export class MdSelect extends _MdSelectMixinBase implements AfterContentInit, On
    * @returns Option that has the corresponding value.
    */
   private _selectValue(value: any, isUserInput = false): MdOption | undefined {
-    let optionsArray = this.options.toArray();
-    let correspondingOption = optionsArray.find(option => {
+    let correspondingOption = this.options.find(option => {
       return option.value != null && option.value === value;
     });
 
     if (correspondingOption) {
       isUserInput ? correspondingOption._selectViaInteraction() : correspondingOption.select();
       this._selectionModel.select(correspondingOption);
-      this._keyManager.setActiveItem(optionsArray.indexOf(correspondingOption));
     }
 
     return correspondingOption;