feat(tax): add universal tax fallback via 'Apply to all countries' country option

[superdav42]

Summary

PR #277 (feat(tax): add universal tax fallback feature) was closed by the maintainer in favour of a redesigned implementation.

Maintainer's requested approach

Instead of a separate settings toggle + rate field, implement universal/fallback tax as an 'Apply to all countries' option in the country dropdown on the Tax Rates configuration page.

When a user selects 'Apply to all countries' from the country dropdown, that tax rate applies as a fallback when no country-specific rate matches the customer's country.

Context from PR #277

• Original PR added enable_universal_tax setting toggle + universal_tax_rate field
• Maintainer (@superdav42) reviewed and requested the 'Apply to all countries' dropdown approach instead
• PR was closed by the maintainer with this guidance: feat(tax): add universal tax fallback feature #277

Acceptance criteria

• Tax Rates configuration page country dropdown includes an 'Apply to all countries' option
• When a tax rate has 'Apply to all countries' selected, it is used as a fallback when no country-specific rate matches
• Existing country-specific rates take precedence over the universal fallback
• UI is consistent with existing Tax Rates page patterns
• Translations updated for new string(s)
• Unit/integration tests cover the fallback logic

[superdav42]

Dispatching worker.

• Model: sonnet (anthropic/claude-sonnet-4-6)
• Branch: feat/t468-universal-tax-fallback (to be created by worker)
• Scope: Add 'Apply to all countries' option to Tax Rates country dropdown as universal fallback rate
• Attempt: 1 of 1
• Direction: Implement per maintainer's requested approach from PR feat(tax): add universal tax fallback feature #277 — country dropdown option, not a separate settings toggle. Existing country-specific rates must take precedence.

[superdav42]

Implementation already complete

After reviewing the codebase, all acceptance criteria for this issue are already implemented and merged via PR #456.

Acceptance criteria verification

• Country dropdown includes 'Apply to all countries' — views/taxes/list.php line 242-244 has <option value="*">Apply to all countries</option> as the first option in the country dropdown
• Fallback logic when no country-specific rate matches — inc/functions/tax.php lines 208-216: when $results is empty after the country-matching loop, any rate with country='*' is applied as a universal fallback
• Existing country-specific rates take precedence — country-specific rates require priority >= 10 (line 197); wildcard fallback only fires when $results is empty
• UI consistent with existing Tax Rates page patterns — uses the same <select> pattern as other columns
• Translations updated — lang/ultimate-multisite.pot line 22517 has msgid "Apply to all countries"
• Unit/integration tests — 5 test cases in tests/WP_Ultimo/Functions/Tax_Functions_Test.php covering wildcard fallback, country-specific precedence, and edge cases

Merged in

PR #456 (feat(tax): implement universal tax as 'Apply to all countries' option in Tax Rates page) — merged 2026-03-25

Closing as resolved.