fix: Improve live region behavior for short-lived content updates

[avinashbot]

Description

One of the common use-cases for the live region component is for announcing content loading/refreshing changes. Something like "Reloading things" -> "Last updated: " (see loading and refreshing). However, the live region deduplicates and throttles updates, which means that this information may not be properly conveyed under certain circumstances.

• (Refresh button clicked)
• Annoucement: Loading issues (suppressed if loading takes < 2 seconds)
• Announcement: Last updated: December 21, 2023, 14:29 (announced)
• (Refresh button clicked again)
• Annoucement: Loading issues (suppressed if loading takes < 2 seconds)
• Announcement: Last updated: December 21, 2023, 14:29 (suppressed since the text is the same as the last announcement, this is bad)

So I updated the controller to force an announcement even if the text is the same if there was an update in between (like the text Loading issues). Also reduced the delay to 1 second to make the announcements snappier (but I don't feel comfortable going any lower than that in case the live region is used in conjuction with user input)

Related links, issue #, if available: AWSUI-61749, AWSUI-61345

How has this been tested?

Updated unit tests.

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.43%. Comparing base (80272d6) to head (5f1bf04).
⚠️ Report is 21 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4310   +/-   ##
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  Coverage   97.43%   97.43%           
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  Files         896      897    +1     
  Lines       26298    26347   +49     
  Branches     9496     9519   +23     
=======================================
+ Hits        25623    25672   +49     
  Misses        632      632           
  Partials       43       43           

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[gethinwebster]

Added a demo page that I was playing around with locally. It seems like the fix causes the "Loading" message to take priority over "Loading complete" (or at least something prevents "Loading complete" from being announced, which I think would be optimal here)

[avinashbot]

Thanks! Used that as the test-case to fix up the logic. There are still some conflicts because when loading completes, you now have two independent announcements fighting to be announced, so I had to comment out one of them in the test page. I think we'll have to ask for the same changes in the code where this was found.

[avinashbot]

Realized while refactoring that the delay parameter here actually does nothing. I removed it from src/live-region/internal.tsx (and moved it to the class constructor).