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fix(select): use combobox pattern for accessibility (#20082)
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Applies some of our recent learnings on how to handle the accessibility of a custom select to `mat-select`. Includes switching the trigger to be a `combobox` and the panel to a `listbox`.

Fixes #11083.
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@crisbeto
crisbeto authored Aug 25, 2020
1 parent f0c7a25 commit 6fbf142
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Showing 5 changed files with 188 additions and 137 deletions.
10 changes: 7 additions & 3 deletions src/material/select/select.html
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Original file line number Diff line number Diff line change
@@ -1,10 +1,9 @@
<div cdk-overlay-origin
class="mat-select-trigger"
aria-hidden="true"
(click)="toggle()"
#origin="cdkOverlayOrigin"
#trigger>
<div class="mat-select-value" [ngSwitch]="empty">
<div class="mat-select-value" [ngSwitch]="empty" [attr.id]="_valueId">
<span class="mat-select-placeholder" *ngSwitchCase="true">{{placeholder || '\u00A0'}}</span>
<span class="mat-select-value-text" *ngSwitchCase="false" [ngSwitch]="!!customTrigger">
<span *ngSwitchDefault>{{triggerValue || '\u00A0'}}</span>
Expand Down Expand Up @@ -32,8 +31,13 @@
<div class="mat-select-panel-wrap" [@transformPanelWrap]>
<div
#panel
[attr.id]="id + '-panel'"
role="listbox"
tabindex="-1"
class="mat-select-panel {{ _getPanelTheme() }}"
[attr.id]="id + '-panel'"
[attr.aria-multiselectable]="multiple"
[attr.aria-label]="ariaLabel || null"
[attr.aria-labelledby]="_getPanelAriaLabelledby()"
[ngClass]="panelClass"
[@transformPanel]="multiple ? 'showing-multiple' : 'showing'"
(@transformPanel.done)="_panelDoneAnimatingStream.next($event.toState)"
Expand Down
217 changes: 122 additions & 95 deletions src/material/select/select.spec.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -145,32 +145,58 @@ describe('MatSelect', () => {
select = fixture.debugElement.query(By.css('mat-select'))!.nativeElement;
}));

it('should set the role of the select to listbox', fakeAsync(() => {
expect(select.getAttribute('role')).toEqual('listbox');
it('should set the role of the select to combobox', fakeAsync(() => {
expect(select.getAttribute('role')).toEqual('combobox');
expect(select.getAttribute('aria-autocomplete')).toBe('none');
expect(select.getAttribute('aria-haspopup')).toBe('true');
}));

it('should set the aria label of the select to the placeholder', fakeAsync(() => {
expect(select.getAttribute('aria-label')).toEqual('Food');
it('should point the aria-controls attribute to the listbox', fakeAsync(() => {
expect(select.hasAttribute('aria-controls')).toBe(false);

fixture.componentInstance.select.open();
fixture.detectChanges();
flush();

const ariaControls = select.getAttribute('aria-controls');
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');

fixture.componentInstance.select.open();
fixture.detectChanges();
flush();

expect(select.getAttribute('aria-expanded')).toBe('true');
}));

it('should support setting a custom aria-label', fakeAsync(() => {
fixture.componentInstance.ariaLabel = 'Custom Label';
fixture.detectChanges();

expect(select.getAttribute('aria-label')).toEqual('Custom Label');
expect(select.hasAttribute('aria-labelledby')).toBeFalsy();
}));

it('should not set an aria-label if aria-labelledby is specified', fakeAsync(() => {
it('should be able to add an extra aria-labelledby on top of the default', fakeAsync(() => {
fixture.componentInstance.ariaLabelledby = 'myLabelId';
fixture.detectChanges();

expect(select.getAttribute('aria-label')).toBeFalsy('Expected no aria-label to be set.');
expect(select.getAttribute('aria-labelledby')).toBe('myLabelId');
const labelId = fixture.nativeElement.querySelector('.mat-form-field-label').id;
const valueId = fixture.nativeElement.querySelector('.mat-select-value').id;

expect(select.getAttribute('aria-labelledby')).toBe(`${labelId} ${valueId} myLabelId`);
}));

it('should not have aria-labelledby in the DOM if it`s not specified', fakeAsync(() => {
it('should set aria-labelledby to the value and label IDs', fakeAsync(() => {
fixture.detectChanges();
expect(select.hasAttribute('aria-labelledby')).toBeFalsy();

const labelId = fixture.nativeElement.querySelector('.mat-form-field-label').id;
const valueId = fixture.nativeElement.querySelector('.mat-select-value').id;
expect(select.getAttribute('aria-labelledby')).toBe(`${labelId} ${valueId}`);
}));

it('should set the tabindex of the select to 0 by default', fakeAsync(() => {
Expand Down Expand Up @@ -237,37 +263,15 @@ describe('MatSelect', () => {
expect(select.getAttribute('tabindex')).toEqual('0');
}));

it('should set `aria-labelledby` to form field label if there is no placeholder', () => {
fixture.destroy();

const labelFixture = TestBed.createComponent(SelectWithFormFieldLabel);
labelFixture.detectChanges();
select = labelFixture.debugElement.query(By.css('mat-select'))!.nativeElement;

expect(select.getAttribute('aria-labelledby')).toBeTruthy();
expect(select.getAttribute('aria-labelledby'))
.toBe(labelFixture.nativeElement.querySelector('label').getAttribute('id'));
});

it('should not set `aria-labelledby` if there is a placeholder', () => {
fixture.destroy();

const labelFixture = TestBed.createComponent(SelectWithFormFieldLabel);
labelFixture.componentInstance.placeholder = 'Thing selector';
labelFixture.detectChanges();
select = labelFixture.debugElement.query(By.css('mat-select'))!.nativeElement;

expect(select.getAttribute('aria-labelledby')).toBeFalsy();
});

it('should not set `aria-labelledby` if there is no form field label', () => {
it('should set `aria-labelledby` to the value ID if there is no form field', () => {
fixture.destroy();

const labelFixture = TestBed.createComponent(SelectWithChangeEvent);
labelFixture.detectChanges();
select = labelFixture.debugElement.query(By.css('mat-select'))!.nativeElement;
const valueId = labelFixture.nativeElement.querySelector('.mat-select-value').id;

expect(select.getAttribute('aria-labelledby')).toBeFalsy();
expect(select.getAttribute('aria-labelledby')?.trim()).toBe(valueId);
});

it('should select options via the UP/DOWN arrow keys on a closed select', fakeAsync(() => {
Expand Down Expand Up @@ -812,28 +816,28 @@ describe('MatSelect', () => {
expect(document.activeElement).toBe(select, 'Expected select element to be focused.');
}));

// Having `aria-hidden` on the trigger avoids issues where
// screen readers read out the wrong amount of options.
it('should set aria-hidden on the trigger element', fakeAsync(() => {
const trigger = fixture.debugElement.query(By.css('.mat-select-trigger'))!.nativeElement;

expect(trigger.getAttribute('aria-hidden'))
.toBe('true', 'Expected aria-hidden to be true when the select is open.');
}));

it('should set `aria-multiselectable` to true on multi-select instances', fakeAsync(() => {
fixture.destroy();

const multiFixture = TestBed.createComponent(MultiSelect);
it('should set `aria-multiselectable` to true on the listbox inside multi select',
fakeAsync(() => {
fixture.destroy();

multiFixture.detectChanges();
select = multiFixture.debugElement.query(By.css('mat-select'))!.nativeElement;
const multiFixture = TestBed.createComponent(MultiSelect);
multiFixture.detectChanges();
select = multiFixture.debugElement.query(By.css('mat-select'))!.nativeElement;
multiFixture.componentInstance.select.open();
multiFixture.detectChanges();
flush();

expect(select.getAttribute('aria-multiselectable')).toBe('true');
}));
const panel = document.querySelector('.mat-select-panel')!;
expect(panel.getAttribute('aria-multiselectable')).toBe('true');
}));

it('should set aria-multiselectable false on single-selection instances', fakeAsync(() => {
expect(select.getAttribute('aria-multiselectable')).toBe('false');
fixture.componentInstance.select.open();
fixture.detectChanges();
flush();

const panel = document.querySelector('.mat-select-panel')!;
expect(panel.getAttribute('aria-multiselectable')).toBe('false');
}));

it('should set aria-activedescendant only while the panel is open', fakeAsync(() => {
Expand Down Expand Up @@ -929,6 +933,47 @@ describe('MatSelect', () => {
expect(document.activeElement).toBe(select, 'Expected trigger to be focused.');
}));

it('should set a role of listbox on the select panel', fakeAsync(() => {
fixture.componentInstance.select.open();
fixture.detectChanges();
flush();

const panel = document.querySelector('.mat-select-panel')!;
expect(panel.getAttribute('role')).toBe('listbox');
}));

it('should point the aria-labelledby of the panel to the field label', fakeAsync(() => {
fixture.componentInstance.select.open();
fixture.detectChanges();
flush();

const labelId = fixture.nativeElement.querySelector('.mat-form-field-label').id;
const panel = document.querySelector('.mat-select-panel')!;
expect(panel.getAttribute('aria-labelledby')).toBe(labelId);
}));

it('should add a custom aria-labelledby to the panel', fakeAsync(() => {
fixture.componentInstance.ariaLabelledby = 'myLabelId';
fixture.componentInstance.select.open();
fixture.detectChanges();
flush();

const labelId = fixture.nativeElement.querySelector('.mat-form-field-label').id;
const panel = document.querySelector('.mat-select-panel')!;
expect(panel.getAttribute('aria-labelledby')).toBe(`${labelId} myLabelId`);
}));

it('should clear aria-labelledby from the panel if an aria-label is set', fakeAsync(() => {
fixture.componentInstance.ariaLabel = 'My label';
fixture.componentInstance.select.open();
fixture.detectChanges();
flush();

const panel = document.querySelector('.mat-select-panel')!;
expect(panel.getAttribute('aria-label')).toBe('My label');
expect(panel.hasAttribute('aria-labelledby')).toBe(false);
}));

});

describe('for options', () => {
Expand Down Expand Up @@ -2223,49 +2268,7 @@ describe('MatSelect', () => {
options = overlayContainerElement.querySelectorAll('mat-option') as NodeListOf<HTMLElement>;
}));

it('should set aria-owns properly', fakeAsync(() => {
const selects = fixture.debugElement.queryAll(By.css('mat-select'));

expect(selects[0].nativeElement.getAttribute('aria-owns'))
.toContain(options[0].id, `Expected aria-owns to contain IDs of its child options.`);
expect(selects[0].nativeElement.getAttribute('aria-owns'))
.toContain(options[1].id, `Expected aria-owns to contain IDs of its child options.`);

const backdrop =
overlayContainerElement.querySelector('.cdk-overlay-backdrop') as HTMLElement;
backdrop.click();
fixture.detectChanges();
flush();

triggers[1].nativeElement.click();
fixture.detectChanges();
flush();

options =
overlayContainerElement.querySelectorAll('mat-option') as NodeListOf<HTMLElement>;
expect(selects[1].nativeElement.getAttribute('aria-owns'))
.toContain(options[0].id, `Expected aria-owns to contain IDs of its child options.`);
expect(selects[1].nativeElement.getAttribute('aria-owns'))
.toContain(options[1].id, `Expected aria-owns to contain IDs of its child options.`);
}));

it('should remove aria-owns when the options are not visible', fakeAsync(() => {
const select = fixture.debugElement.query(By.css('mat-select'))!;

expect(select.nativeElement.hasAttribute('aria-owns'))
.toBe(true, 'Expected select to have aria-owns while open.');

const backdrop =
overlayContainerElement.querySelector('.cdk-overlay-backdrop') as HTMLElement;
backdrop.click();
fixture.detectChanges();
flush();

expect(select.nativeElement.hasAttribute('aria-owns'))
.toBe(false, 'Expected select not to have aria-owns when closed.');
}));

it('should set the option id properly', fakeAsync(() => {
it('should set the option id', fakeAsync(() => {
let firstOptionID = options[0].id;

expect(options[0].id)
Expand Down Expand Up @@ -4590,6 +4593,13 @@ describe('MatSelect', () => {
expect(select.disableOptionCentering).toBe(true);
expect(select.typeaheadDebounceInterval).toBe(1337);
});

it('should not not throw if the select is inside an ng-container with ngIf', fakeAsync(() => {
configureMatSelectTestingModule([SelectInNgContainer]);
const fixture = TestBed.createComponent(SelectInNgContainer);
expect(() => fixture.detectChanges()).not.toThrow();
}));

});


Expand Down Expand Up @@ -5430,3 +5440,20 @@ class SelectWithResetOptionAndFormControl {
@ViewChildren(MatOption) options: QueryList<MatOption>;
control = new FormControl();
}


@Component({
selector: 'select-with-placeholder-in-ngcontainer-with-ngIf',
template: `
<mat-form-field>
<ng-container *ngIf="true">
<mat-select placeholder="Product Area">
<mat-option value="a">A</mat-option>
<mat-option value="b">B</mat-option>
<mat-option value="c">C</mat-option>
</mat-select>
</ng-container>
</mat-form-field>
`
})
class SelectInNgContainer {}
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