fix(mobile): polyfill Intl.PluralRules on Hermes - #5499
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Fixes KILO-APP-5S Hermes ships without Intl.PluralRules. The FormatJS NumberFormat polyfill constructs one, so every formatNumber call on a device threw "undefined is not a function" and the tabs layout crashed at startup. Load the PluralRules polyfill and its locale data before the NumberFormat polyfill. The Hermes test no longer stubs PluralRules as present.
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Code Review SummaryStatus: No Issues Found | Recommendation: Merge Files Reviewed (3 files)
Previous Review Summary (commit 8927752)Current summary above is authoritative. Previous snapshots are kept for context only. Previous review (commit 8927752)Status: No Issues Found | Recommendation: Merge Files Reviewed (5 files)
Reviewed by grok-4.6 · Input: 111.6K · Output: 15.6K · Cached: 525.6K Review guidance: REVIEW.md from base branch |
pandemicsyn
approved these changes
Aug 25, 2026
i18next builds its own Intl.PluralRules per language and caches the result. If the polyfill is not in place before the first render in the new language, it caches the English one/other fallback for that language. Run prewarmIntl before changeLanguage at both call sites. Add a test that stubs the real Hermes Intl surface and exercises every formatter for every supported language, plus i18next plural selection.
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Summary
Fixes KILO-APP-5S: TestFlight build 1.0.6 (156) crashes at startup with
Error: undefined is not a function.Intl.PluralRules. The FormatJS NumberFormat polyfill callsnew Intl.PluralRules(...), so the firstformatNumbercall (tab accessibility labels inTabsLayout) threw.@formatjs/intl-pluralrulesand load it, with locale data, before the NumberFormat polyfill.Intl.PluralRulesper language and caches the English one/other fallback when it is missing. RunprewarmIntlbeforechangeLanguageat both call sites so the polyfill is in place first.main.Hermes audit
Grepped
apps/mobile/srcandpackages/app-sharedfor features Hermes lacks (structuredClone,Object.groupBy, Set methods, iterator helpers,toSorted, RegExpd/vflags,Intl.DisplayNames/Locale/Segmenterdirect use). No other hits in app code. EveryIntlconstructor routes throughintl-cache.ts.Test plan
pnpm typecheck && pnpm lint && pnpm check:unused && pnpm testinapps/mobile