fix(material/select): make VoiceOver read options for selects in dialogs

Fixes #20694

@zelliot noted that this issue was caused by `aria-modal` preventing
VoiceOver from accessing the select's listbox overlay. He suggested
using `aria-owns` to re-parent the overlay element to the select
trigger. I tried this and it works great.

Author: jelbourn

src/dev-app/select/BUILD.bazel

@@ -12,6 +12,7 @@ ng_module(
     deps = [
         "//src/material/button",
         "//src/material/card",
+        "//src/material/dialog",
         "//src/material/form-field",
         "//src/material/icon",
         "//src/material/input",

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

@@ -11,6 +11,7 @@ import {NgModule} from '@angular/core';
 import {FormsModule, ReactiveFormsModule} from '@angular/forms';
 import {MatButtonModule} from '@angular/material/button';
 import {MatCardModule} from '@angular/material/card';
+import {MatDialogModule} from '@angular/material/dialog';
 import {MatFormFieldModule} from '@angular/material/form-field';
 import {MatIconModule} from '@angular/material/icon';
 import {MatInputModule} from '@angular/material/input';
@@ -24,6 +25,7 @@ import {SelectDemo} from './select-demo';
     FormsModule,
     MatButtonModule,
     MatCardModule,
+    MatDialogModule,
     MatFormFieldModule,
     MatIconModule,
     MatInputModule,

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

@@ -246,6 +246,33 @@
     </mat-card>
   </div>
 
+  <mat-card>
+    <mat-card-subtitle>MatSelect inside a dialog</mat-card-subtitle>
+    <mat-card-content>
+
+      <button (click)="openDialogWithSelectInside(dialogTemplate)">Open dialog</button>
+
+      <ng-template #dialogTemplate>
+        <mat-form-field>
+          <mat-label>Your name</mat-label>
+          <input matInput>
+        </mat-form-field>
+
+        <mat-form-field>
+          <mat-label>Select a topping</mat-label>
+          <mat-select>
+            <mat-option>Cheese</mat-option>
+            <mat-option>Onion</mat-option>
+            <mat-option>Pepper</mat-option>
+          </mat-select>
+        </mat-form-field>
+
+        <button>Done</button>
+      </ng-template>
+
+    </mat-card-content>
+  </mat-card>
+
 </div>
 
 <mat-card class="demo-card demo-basic">

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

@@ -6,9 +6,10 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {Component} from '@angular/core';
+import {Component, TemplateRef} from '@angular/core';
 import {FormControl, Validators} from '@angular/forms';
 import {ErrorStateMatcher, ThemePalette} from '@angular/material/core';
+import {MatDialog} from '@angular/material/dialog';
 import {FloatLabelType} from '@angular/material/form-field';
 import {MatSelectChange} from '@angular/material/select';
 
@@ -23,9 +24,9 @@ export class MyErrorStateMatcher implements ErrorStateMatcher {
 }
 
 @Component({
-    selector: 'select-demo',
-    templateUrl: 'select-demo.html',
-    styleUrls: ['select-demo.css'],
+  selector: 'select-demo',
+  templateUrl: 'select-demo.html',
+  styleUrls: ['select-demo.css'],
 })
 export class SelectDemo {
   drinksRequired = false;
@@ -133,6 +134,8 @@ export class SelectDemo {
     {value: 'indramon-5', viewValue: 'Indramon'}
   ];
 
+  constructor(private dialog: MatDialog) {}
+
   toggleDisabled() {
     this.foodControl.enabled ? this.foodControl.disable() : this.foodControl.enable();
   }
@@ -158,4 +161,8 @@ export class SelectDemo {
   toggleSelected() {
     this.currentAppearanceValue = this.currentAppearanceValue ? null : this.digimon[0].value;
   }
+
+  openDialogWithSelectInside(dialogTemplate: TemplateRef<unknown>) {
+    this.dialog.open(dialogTemplate);
+  }
 }

src/material-experimental/mdc-select/select.spec.ts

@@ -196,6 +196,18 @@ describe('MDC-based MatSelect', () => {
           expect(ariaControls).toBe(document.querySelector('.mat-mdc-select-panel')!.id);
         }));
 
+        it('should point the aria-owns attribute to the listbox', fakeAsync(() => {
+          expect(select.hasAttribute('aria-owns')).toBe(false);
+
+          fixture.componentInstance.select.open();
+          fixture.detectChanges();
+          flush();
+
+          const ariaControls = select.getAttribute('aria-owns');
+          expect(ariaControls).toBeTruthy();
+          expect(ariaControls).toBe(document.querySelector('.mat-mdc-select-panel')!.id);
+        }));
+
         it('should set aria-expanded based on the select open state', fakeAsync(() => {
           expect(select.getAttribute('aria-expanded')).toBe('false');
 

src/material-experimental/mdc-select/select.ts

@@ -62,6 +62,13 @@ export class MatSelectTrigger {}
     'class': 'mat-mdc-select',
     '[attr.id]': 'id',
     '[attr.tabindex]': 'tabIndex',
+    // While aria-owns is not required for the `role="combobox"` interaction pattern,
+    // it fixes an issue with VoiceOver when the select appears inside of an `aria-model="true"`
+    // element (e.g. a dialog). Without `aria-owns`, the `aria-modal` on a dialog would prevent
+    // VoiceOver from "seeing" the select's listbox overlay for aria-activedescendant.
+    // Using `aria-owns` re-parents the select overlay so that it works again.
+    // See https://github.com/angular/components/issues/20694
+    '[attr.aria-owns]': 'panelOpen ? id + "-panel" : null',
     '[attr.aria-controls]': 'panelOpen ? id + "-panel" : null',
     '[attr.aria-expanded]': 'panelOpen',
     '[attr.aria-label]': 'ariaLabel || null',

src/material/select/select.spec.ts

@@ -165,6 +165,18 @@ describe('MatSelect', () => {
           expect(ariaControls).toBe(document.querySelector('.mat-select-panel')!.id);
         }));
 
+        it('should point the aria-controls attribute to the listbox', fakeAsync(() => {
+          expect(select.hasAttribute('aria-owns')).toBe(false);
+
+          fixture.componentInstance.select.open();
+          fixture.detectChanges();
+          flush();
+
+          const ariaControls = select.getAttribute('aria-owns');
+          expect(ariaControls).toBeTruthy();
+          expect(ariaControls).toBe(document.querySelector('.mat-select-panel')!.id);
+        }));
+
         it('should set aria-expanded based on the select open state', fakeAsync(() => {
           expect(select.getAttribute('aria-expanded')).toBe('false');
 

src/material/select/select.ts

@@ -1105,12 +1105,19 @@ export abstract class _MatSelectBase<C> extends _MatSelectMixinBase implements A
     'role': 'combobox',
     'aria-autocomplete': 'none',
     // TODO(crisbeto): the value for aria-haspopup should be `listbox`, but currently it's difficult
-    // to sync into g3, because of an outdated automated a11y check which flags it as an invalid
+    // to sync into Google, because of an outdated automated a11y check which flags it as an invalid
     // value. At some point we should try to switch it back to being `listbox`.
     'aria-haspopup': 'true',
     'class': 'mat-select',
     '[attr.id]': 'id',
     '[attr.tabindex]': 'tabIndex',
+    // While aria-owns is not required for the `role="combobox"` interaction pattern,
+    // it fixes an issue with VoiceOver when the select appears inside of an `aria-model="true"`
+    // element (e.g. a dialog). Without `aria-owns`, the `aria-modal` on a dialog would prevent
+    // VoiceOver from "seeing" the select's listbox overlay for aria-activedescendant.
+    // Using `aria-owns` re-parents the select overlay so that it works again.
+    // See https://github.com/angular/components/issues/20694
+    '[attr.aria-owns]': 'panelOpen ? id + "-panel" : null',
     '[attr.aria-controls]': 'panelOpen ? id + "-panel" : null',
     '[attr.aria-expanded]': 'panelOpen',
     '[attr.aria-label]': 'ariaLabel || null',