Dashboard: Fix domain expiry sort crash when expiry is undefined

[StevenDufresne]

Fixes CALYPSO-2HDV
Fixes DOTMSD-1092

Proposed Changes

• Extract a generic sortNullableStrings comparator into its own module for reuse and testability.
• Fix the sort function to compare getValue results directly instead of accessing .expiry on them. The @wordpress/dataviews library calls getValue on each item first, then passes those results to field.sort — the original code incorrectly treated the sort arguments as full DomainSummary objects.
• Add unit tests covering null, undefined, ascending, descending, and equal value cases.

Why are these changes being made?

The domain expiry sort in the Dashboard domains DataView was broken in two ways:

1. It only guarded against null expiry values, but some domains have undefined expiry at runtime, causing a TypeError crash (CALYPSO-2HDV — 4 occurrences, 3 users impacted).
2. Even without the crash, the sort never worked correctly because the @wordpress/dataviews library wraps field.sort — it calls getValue first and passes the category strings ('1-expired', '2-next-90-days', '3-more-than-90-days') to sort, not full DomainSummary objects. The old code did a.expiry.localeCompare(b.expiry) on these strings, which silently failed.

Testing Instructions

• Navigate to the Domains page in the Dashboard (/domains)
• Sort domains by the "Paid until" column (click the column header)
• Verify expired domains sort before expiring-soon domains, which sort before others
• Verify toggling the sort direction reverses the order
• Verify domains with no expiry date sort to the end

Pre-merge Checklist

• Has the general commit checklist been followed? (PCYsg-hS-p2)
• Have you written new tests for your changes?
• Have you tested the feature in Simple (P9HQHe-k8-p2), Atomic (P9HQHe-jW-p2), and self-hosted Jetpack sites (PCYsg-g6b-p2)?
• Have you checked for TypeScript, React or other console errors?
• Have you tested accessibility for your changes? Ensure the feature remains usable with various user agents (e.g., browsers), interfaces (e.g., keyboard navigation), and assistive technologies (e.g., screen readers) (PCYsg-S3g-p2).
• Have you used memoizing on expensive computations? More info in Memoizing with create-selector and Using memoizing selectors and Our Approach to Data
• Have we added the "[Status] String Freeze" label as soon as any new strings were ready for translation (p4TIVU-5Jq-p2)?
  • For UI changes, have we tested the change in various languages (for example, ES, PT, FR, or DE)? The length of text and words vary significantly between languages.
• For changes affecting Jetpack: Have we added the "[Status] Needs Privacy Updates" label if this pull request changes what data or activity we track or use (p4TIVU-aUh-p2)?

[github-actions]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-169260

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-169260&env=jetpack

Automattic for Agencies live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-169260&env=a8c-for-agencies

Dashboard live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-169260&env=dashboard

[matticbot]

This PR modifies the release build for the following Calypso Apps:

For info about this notification, see here: PCYsg-OT6-p2

• help-center
• notifications

To test WordPress.com changes, run install-plugin.sh $pluginSlug StevenDufresne/fix-domain-expiry-sort on your sandbox.

[fushar]

Tested, works.

[fushar]

This comment is now not necessary :)

[StevenDufresne]

🐒 🙈

[fushar]

I'll commandeer this. It seems to have broken production in my case 😬

[StevenDufresne]

Thanks. I was coming online to do so today :)