feat(ByRole): Improve perf if multiple elements are found

[eps1lon]

What:

Improves perf >20% reduction if ByRole returns multiple elements. The more elements the bigger the reduction

Why:

Perf concerns were raised about isInaccessible

How:

An element being inaccessible does not imply every descendant is inaccessible because elements can re-appear by setting visibility: visible in a visibility: hidden subtree. However, they can't override hidden or aria-hidden=true or display: none. So we cache isSubtreeInaccessible return values for each element. For collections of elements (e.g. option or listitem) this reduces getComputedStyle calls from O(n * depth(n)) to O(n) + O(depth(n)) where n is the number of elements of the given role. It enables a very fast best case for collections where the containing element (e.g. the listbox) is hidden. We only have to compute the style once for subsequent listitems and can exit early once we hit the listbox and the cache subtreeIsInaccessible returns true.

To avoid passing the computed style too much around I removed getComputedStyle().visibility compatibility for jsdom < 15.2. Once jest 25 is released this will be fixed for jest users anyway and CSS was one of the lesser concerns of other collaborators.

We use a WeakMap for the cache. Those are supported in IE 11: https://caniuse.com/#search=Weakmap

Checklist:

• [ ] Documentation added to the
  docs site
• [ ] I've prepared a PR for types targeting
  DefinitelyTyped
• Tests
• Ready to be merged
  • review
  • testing canary in Material-UI [test] Use @testing-library/dom canary mui/material-ui#18021
  • enchmark removal

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[kentcdodds]

An element being inaccessible does not imply every descendant is inaccessible because elements can re-appear by setting visibility: visible in a visibility: hidden subtree.

Ah rats. What a shame! Haha. Thank you so much for working on this @eps1lon! I appreciate your help on this.

[kentcdodds]

🎉 This PR is included in version 6.9.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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