fix(material/chips): implement ariaDescription with aria-describedby

For the `ariaDescription` Input, implement with aria-describedby rather
than aria-description. aria-description is still in W3C Editor's Draft for ARIA
1.3.

Author: zarend

src/material/chips/chip-option.html

@@ -11,7 +11,7 @@
     [_allowFocusWhenDisabled]="true"
     [attr.aria-selected]="ariaSelected"
     [attr.aria-label]="ariaLabel"
-    [attr.aria-description]="ariaDescription"
+    [attr.aria-describedby]="_ariaDescriptionId"
     role="option">
     <span class="mdc-evolution-chip__graphic mat-mdc-chip-graphic">
       <ng-content select="mat-chip-avatar, [matChipAvatar]"></ng-content>
@@ -34,3 +34,5 @@
   *ngIf="_hasTrailingIcon()">
   <ng-content select="mat-chip-trailing-icon,[matChipRemove],[matChipTrailingIcon]"></ng-content>
 </span>
+
+<span class="cdk-visually-hidden" [id]="_ariaDescriptionId">{{ariaDescription}}</span>

src/material/chips/chip-option.spec.ts

@@ -308,8 +308,28 @@ describe('MDC-based Option Chips', () => {
           .withContext('expected to find an element with option role')
           .toBeTruthy();
 
-        expect(optionElement.getAttribute('aria-label')).toBe('option name');
-        expect(optionElement.getAttribute('aria-description')).toBe('option description');
+        expect(optionElement.getAttribute('aria-label')).toMatch(/option name/i);
+
+        const optionElementDescribedBy = optionElement!.getAttribute('aria-describedby');
+        expect(optionElementDescribedBy)
+          .withContext('expected primary grid cell to have a non-empty aria-describedby attribute')
+          .toBeTruthy();
+
+        const optionElementDescriptions = Array.from(
+          (fixture.nativeElement as HTMLElement).querySelectorAll(
+            optionElementDescribedBy!
+              .split(/\s+/g)
+              .map(x => `#${x}`)
+              .join(','),
+          ),
+        );
+
+        const optionElementDescription = optionElementDescriptions
+          .map(x => x.textContent?.trim())
+          .join(' ')
+          .trim();
+
+        expect(optionElementDescription).toMatch(/option description/i);
       });
     });
 

src/material/chips/chip-option.ts

@@ -31,6 +31,8 @@ export class MatChipSelectionChange {
   ) {}
 }
 
+let id = 1;
+
 /**
  * An extension of the MatChip component that supports chip selection. Used with MatChipListbox.
  *
@@ -178,4 +180,7 @@ export class MatChipOption extends MatChip implements OnInit {
       this._changeDetectorRef.markForCheck();
     }
   }
+
+  /** Id of a span that contains this chip's aria description. @docs-private */
+  _ariaDescriptionId = `chip-option-${id++}-aria-description`;
 }

src/material/chips/chip-row.html

@@ -14,7 +14,7 @@
     [tabIndex]="tabIndex"
     [disabled]="disabled"
     [attr.aria-label]="ariaLabel"
-    [attr.aria-description]="ariaDescription">
+    [attr.aria-describedby]="_ariaDescriptionId">
     <span class="mdc-evolution-chip__graphic mat-mdc-chip-graphic" *ngIf="leadingIcon">
       <ng-content select="mat-chip-avatar, [matChipAvatar]"></ng-content>
     </span>
@@ -38,3 +38,5 @@
   *ngIf="_hasTrailingIcon()">
   <ng-content select="mat-chip-trailing-icon,[matChipRemove],[matChipTrailingIcon]"></ng-content>
 </span>
+
+<span class="cdk-visually-hidden" [id]="_ariaDescriptionId">{{ariaDescription}}</span>

src/material/chips/chip-row.spec.ts

@@ -340,15 +340,35 @@ describe('MDC-based Row Chips', () => {
 
         fixture.detectChanges();
 
-        const primaryGridCell = fixture.nativeElement.querySelector(
+        const primaryGridCell = (fixture.nativeElement as HTMLElement).querySelector(
           '[role="gridcell"].mdc-evolution-chip__cell--primary .mat-mdc-chip-action',
         );
         expect(primaryGridCell)
           .withContext('expected to find the grid cell for the primary chip action')
           .toBeTruthy();
 
-        expect(primaryGridCell.getAttribute('aria-label')).toBe('chip name');
-        expect(primaryGridCell.getAttribute('aria-description')).toBe('chip description');
+        expect(primaryGridCell!.getAttribute('aria-label')).toMatch(/chip name/i);
+
+        const primaryGridCellDescribedBy = primaryGridCell!.getAttribute('aria-describedby');
+        expect(primaryGridCellDescribedBy)
+          .withContext('expected primary grid cell to have a non-empty aria-describedby attribute')
+          .toBeTruthy();
+
+        const primaryGridCellDescriptions = Array.from(
+          (fixture.nativeElement as HTMLElement).querySelectorAll(
+            primaryGridCellDescribedBy!
+              .split(/\s+/g)
+              .map(x => `#${x}`)
+              .join(','),
+          ),
+        );
+
+        const primaryGridCellDescription = primaryGridCellDescriptions
+          .map(x => x.textContent?.trim())
+          .join(' ')
+          .trim();
+
+        expect(primaryGridCellDescription).toMatch(/chip description/i);
       });
     });
   });

src/material/chips/chip-row.ts

@@ -33,6 +33,8 @@ import {MatChipEditInput} from './chip-edit-input';
 import {takeUntil} from 'rxjs/operators';
 import {MAT_CHIP} from './tokens';
 
+let id = 1;
+
 /** Represents an event fired on an individual `mat-chip` when it is edited. */
 export interface MatChipEditedEvent extends MatChipEvent {
   /** The final edit value. */
@@ -212,4 +214,7 @@ export class MatChipRow extends MatChip implements AfterViewInit {
   private _getEditInput(): MatChipEditInput {
     return this.contentEditInput || this.defaultEditInput!;
   }
+
+  /** Id of a span that contains this chip's aria description. @docs-private */
+  _ariaDescriptionId = `chip-row-${id++}-aria-description`;
 }

src/material/chips/chip.ts

@@ -147,9 +147,15 @@ export class MatChip
   /** A unique id for the chip. If none is supplied, it will be auto-generated. */
   @Input() id: string = `mat-mdc-chip-${uid++}`;
 
+  // TODO(#26104): Consider deprecating and using `_computeAriaAccessibleName` instead.
+  // `ariaLabel` may be unnecessary, and `_computeAriaAccessibleName` only supports
+  // datepicker's use case.
   /** ARIA label for the content of the chip. */
   @Input('aria-label') ariaLabel: string | null = null;
 
+  // TODO(#26104): Consider deprecating and using `_computeAriaAccessibleName` instead.
+  // `ariaDescription` may be unnecessary, and `_computeAriaAccessibleName` only supports
+  // datepicker's use case.
   /** ARIA description for the content of the chip. */
   @Input('aria-description') ariaDescription: string | null = null;