fix(chips): chip list removing focus from first chip when adding through the input (#12840)

Fix regression in 3da390e. Currently when the user removes all the chips and then they add a new chip, the chip list will remove focus from the input and put it on the chip. These changes introduce the proper behavior, which is to keep focus on the input.

Author: crisbeto

src/lib/chips/chip-list.spec.ts

@@ -17,6 +17,7 @@ import {
   dispatchFakeEvent,
   dispatchKeyboardEvent,
   dispatchMouseEvent,
+  typeInElement,
   MockNgZone,
 } from '@angular/cdk/testing';
 import {
@@ -993,6 +994,31 @@ describe('MatChipList', () => {
         .not.toBeNull(`Expected placeholder to have an asterisk, as control was required.`);
     });
 
+    it('should keep focus on the input after adding the first chip', fakeAsync(() => {
+      const nativeInput = fixture.nativeElement.querySelector('input');
+      const chipEls = Array.from(fixture.nativeElement.querySelectorAll('.mat-chip')).reverse();
+
+      // Remove the chips via backspace to simulate the user removing them.
+      chipEls.forEach((chip: HTMLElement) => {
+        chip.focus();
+        dispatchKeyboardEvent(chip, 'keydown', BACKSPACE);
+        fixture.detectChanges();
+        tick();
+      });
+
+      nativeInput.focus();
+      expect(fixture.componentInstance.foods).toEqual([], 'Expected all chips to be removed.');
+      expect(document.activeElement).toBe(nativeInput, 'Expected input to be focused.');
+
+      typeInElement('123', nativeInput);
+      fixture.detectChanges();
+      dispatchKeyboardEvent(nativeInput, 'keydown', ENTER);
+      fixture.detectChanges();
+      tick();
+
+      expect(document.activeElement).toBe(nativeInput, 'Expected input to remain focused.');
+    }));
+
     describe('keyboard behavior', () => {
       beforeEach(() => {
         chipListDebugElement = fixture.debugElement.query(By.directive(MatChipList));
@@ -1322,7 +1348,7 @@ class MultiSelectionChipList {
     <mat-form-field>
       <mat-chip-list [multiple]="true"
                     placeholder="Food" [formControl]="control" [required]="isRequired" #chipList1>
-        <mat-chip *ngFor="let food of foods" [value]="food.value">
+        <mat-chip *ngFor="let food of foods" [value]="food.value" (removed)="remove(food)">
           {{ food.viewValue }}
         </mat-chip>
       </mat-chip-list>
@@ -1369,6 +1395,14 @@ class InputChipList {
     }
   }
 
+  remove(food: any): void {
+    const index = this.foods.indexOf(food);
+
+    if (index > -1) {
+      this.foods.splice(index, 1);
+    }
+  }
+
   @ViewChild(MatChipList) chipList: MatChipList;
   @ViewChildren(MatChip) chips: QueryList<MatChip>;
 }

src/lib/chips/chip-list.ts

@@ -498,18 +498,15 @@ export class MatChipList extends _MatChipListMixinBase implements MatFormFieldCo
   }
 
   /**
-   * If the amount of chips changed, we need to update the key manager state and make sure
-   * that to so that we can refocus the
-   * next closest one.
+   * If the amount of chips changed, we need to update the
+   * key manager state and focus the next closest chip.
    */
   protected _updateFocusForDestroyedChips() {
-    if (this._lastDestroyedChipIndex == null || !this.chips.length) {
-      return;
+    if (this._lastDestroyedChipIndex != null && this.chips.length) {
+      const newChipIndex = Math.min(this._lastDestroyedChipIndex, this.chips.length - 1);
+      this._keyManager.setActiveItem(newChipIndex);
     }
 
-    const newChipIndex = Math.min(this._lastDestroyedChipIndex, this.chips.length - 1);
-
-    this._keyManager.setActiveItem(newChipIndex);
     this._lastDestroyedChipIndex = null;
   }