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fix(a11y): don't set aria description if it's the same as the node's aria-label #15250

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Merged
merged 1 commit into from
Feb 22, 2019
Merged

fix(a11y): don't set aria description if it's the same as the node's aria-label #15250

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7 changes: 7 additions & 0 deletions src/cdk/a11y/aria-describer/aria-describer.spec.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -132,6 +132,13 @@ describe('AriaDescriber', () => {
// Use `querySelectorAll` with an attribute since `getElementById` will stop at the first match.
expect(document.querySelectorAll(`[id='${MESSAGES_CONTAINER_ID}']`).length).toBe(1);
});

it('should not describe messages that match up with the aria-label of the element', () => {
component.element1.setAttribute('aria-label', 'Hello');
ariaDescriber.describe(component.element1, 'Hello');
ariaDescriber.describe(component.element1, 'Hi');
expectMessages(['Hi']);
});
});

function getMessagesContainer() {
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18 changes: 15 additions & 3 deletions src/cdk/a11y/aria-describer/aria-describer.ts
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Expand Up @@ -83,7 +83,7 @@ export class AriaDescriber implements OnDestroy {

/** Removes the host element's aria-describedby reference to the message element. */
removeDescription(hostElement: Element, message: string) {
if (!this._canBeDescribed(hostElement, message)) {
if (!this._isElementNode(hostElement)) {
return;
}

Expand Down Expand Up @@ -218,10 +218,22 @@ export class AriaDescriber implements OnDestroy {

/** Determines whether a message can be described on a particular element. */
private _canBeDescribed(element: Element, message: string): boolean {
return element.nodeType === this._document.ELEMENT_NODE && message != null &&
!!`${message}`.trim();
if (!this._isElementNode(element)) {
return false;
}

const trimmedMessage = message == null ? '' : `${message}`.trim();
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Unnecessary template string literal? Also, omit the == null?

message ? '' : message.trim();

Alternatively,

const trimmedMessage = `${message || ''}`.trim();

The function signature also indicates that message can't be null or undefined. Should it include those?

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``${message || ''}.trim(); will swallow values like `0` or `false`. Even though the signature doesn't allow these values, we have some cases where the values from the view get passed straight into this method.

const ariaLabel = element.getAttribute('aria-label');

// We shouldn't set descriptions if they're exactly the same as the `aria-label` of the element,
// because screen readers will end up reading out the same text twice in a row.
return trimmedMessage ? (!ariaLabel || ariaLabel.trim() !== trimmedMessage) : false;
}

/** Checks whether a node is an Element node. */
private _isElementNode(element: Node): element is Element {
return element.nodeType === this._document.ELEMENT_NODE;
}
}


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