RomM Frontend: i18n / Localization

User-visible strings are never hard-coded in components; they come from locale files via vue-i18n ($t(...) in templates/composites; utils may call i18n.global.t(...); v2 lib primitives must not call $t at all, text passes via props/slots).

Structure

• Locales live in frontend/src/locales/<locale>/<namespace>.json, loaded by dynamic glob import in src/locales/index.ts.
• 18 locales: en_US (default + fallback), en_GB, bg_BG, cs_CZ, de_DE, es_ES, fr_FR, hu_HU, it_IT, ja_JP, ko_KR, pl_PL, pt_BR, ro_RO, ru_RU, tr_TR, zh_CN, zh_TW.
• Namespaces are per-feature files (e.g. collection, common, console, detail, emulator, gallery, home, library, login, navigation, patcher, platform, scan, settings, task).

The rule (enforced in CI)

• en_US is the source of truth, but every key added to en_US must be added to all other locale directories in the same change. Never leave a key English-only.
• en_US uses US spelling: "favorites", "color", "canceled". British forms belong in en_GB only. This bites tests too: an e2e or unit assertion on a label must expect the en_US string.
• Actually translate the value into each locale's language: never paste English into non-English locales.
• Editing an existing string counts: changing en_US means re-translating that key in every other locale.
• Reuse each locale's established terms: grep a sibling key for how it renders "metadata", "provider", etc.
• Copying the English value is a last-resort placeholder, only when no translation is available, and must be flagged to revisit.
• Removing or renaming a key means doing it across every locale.

Verify before handoff

python3 frontend/src/locales/check_i18n_locales.py
python3 frontend/src/locales/check_i18n_sorted.py   # add --fix to auto-sort

check_i18n_locales.py compares every non-English locale against en_US and fails on any missing file, missing key, or extra key. check_i18n_sorted.py fails if any locale JSON file's keys aren't sorted alphabetically (run with --fix to sort them in place). CI runs both scripts (.github/workflows/i18n.yml) on any change under frontend/src/locales/**; both must pass.

Adding a new language

Create a new folder under frontend/src/locales/ mirroring en_US/'s files, then translate. Open the PR against master (see the docs/Contributing flow). This is the one i18n change where a new locale directory is expected.