fix(tooltip): avoid adding same aria description as trigger's aria-label #16870
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We automatically add an `aria-describedby` to the triggers of tooltips so that assistive technologies can read out the tooltip text. As a part of this process, the `AriaDescriber` has some functionality that checks whether the element doesn't have an `aria-label` with the same value already, and if it does, it avoids adding the description. The problem is that tooltips add this description very early in their lifecycle which means that if the element has a data-bound `aria-label`, it won't be detected by the `AriaDescriber`, as is the case for the buttons in the `mat-paginator`. These changes work around the issue by deferring the setting of the description. Fixes angular#16719.
crisbeto
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crisbeto
commented
Aug 24, 2019
| // same as the `aria-label` of an element, however we can't know whether the tooltip trigger | ||
| // has a data-bound `aria-label` or when it'll be set for the first time. We can avoid the | ||
| // issue by deferring the description by a tick so Angular has time to set the `aria-label`. | ||
| Promise.resolve().then(() => { |
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For the record, I'm not a fan of having to add this, but it's the least evil of all the alternatives I could think of (e.g. doing our own change detection in one of the after*Checked hooks to see if there's an aria-label or adding a MutationObserver).
jelbourn
approved these changes
Aug 26, 2019
jelbourn
added
pr: lgtm
action: merge
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We automatically add an
aria-describedbyto the triggers of tooltips so that assistive technologies can read out the tooltip text. As a part of this process, theAriaDescriberhas some functionality that checks whether the element doesn't have anaria-labelwith the same value already, and if it does, it avoids adding the description. The problem is that tooltips add this description very early in their lifecycle which means that if the element has a data-boundaria-label, it won't be detected by theAriaDescriber, as is the case for the buttons in themat-paginator. These changes work around the issue by deferring the setting of the description.Fixes #16719.