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Choosing a language other than English or Chinese makes the frontend fetch `./locales/<locale>.json`, which React Native never ships: only `bundled_devtools_locales` (`en-US` and `zh`, set upstream in `config/gni/i18n.gni`) are packaged, and the rest are meant to come from Chrome's `remoteBase` CDN, which React Native never passes. The dev server logs `Error: ENOENT: no such file or directory, stat '…/core/i18n/locales/it.json'` on every launch, and the frontend falls back to English only once the failed request comes back. Users get there without looking for it: with the default setting, a system language that DevTools supports shows the "DevTools is now available in …" infobar on first launch, and both of its buttons pick a locale React Native can't load. The Settings language dropdown lists every one of about 80 locales too. When there is no remote base, build the supported-locale list from the bundled locales only. The language dropdown then offers English and Chinese, the infobar appears only for Chinese, and a stored unbundled locale (or "Browser UI language" on, say, an Italian system) resolves to `en-US` without a request. With a remote base, every locale is offered as before. Fixes react/react-native#52461
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Summary
Mitigates react/react-native#52461. A full fix would be to set up and serve all locale sources via the RN dev server, which I'm not attempting today. English stays a harder default for now.
The bug
DevTools currently presents a language dropdown when the viewer locale is detected. Choosing a language other than English or Chinese makes the frontend fetch
./locales/<locale>.json, which React Native never ships: onlybundled_devtools_locales(en-USandzh, set upstream inconfig/gni/i18n.gni) are packaged, and the rest are meant to come from Chrome'sremoteBaseCDN, which React Native never passes.This leads to the dev server logging
Error: ENOENT: no such file or directory, stat '…/core/i18n/locales/it.json'on every launch.This fix (scoping down available locales to only those bundled) resolves the issue.
Test plan
Served the frontend from a static server that answers 404 for missing files, like Metro, and loaded
rn_fusebox.htmlin headless Chrome for Testing withnavigator.languageset. Before is the published@react-native/debugger-frontend@0.88.0; after is this commit's release GN build (is_debug=false, so noen-XL) with locales other thanen-USandzhremoved, as in the published package.Italian system language, default setting. Before: "DevTools is now available in Italian" with "Always match Chrome's language" and "Switch DevTools to Italian". After: no infobar.
Settings > Preferences > Language. Before: 83 options. After: "Browser UI language", "English (US)" and "Chinese". Headless Chrome draws no native popup, so each image is the dropdown's own
<select>withsizeset to its option count.After, with an Italian system language and the setting stored as
itorbrowserLanguage: onlyen-US.jsonis requested, with no 404 and no fallback warning.After, with a Chinese system language: the Chinese infobar still shows by default, and with the setting
zhorbrowserLanguage,zh.jsonloads (200) and the UI renders in Chinese.npm test -- front_end/core/i18n: 56 of 56 pass, including two new tests that only bundled locales are offered and resolved without a remote base.npm run lint -- front_end/core/i18n/i18nImpl.ts front_end/core/i18n/i18n.test.tspasses.Not covered: this commit in the RN DevTools desktop app with a real app attached.
This change maintains backwards compatibility with previous Local Storage data (if modifying settings, experiments, or other persisted client state).
Upstreaming plan
devtools-frontendrepo following the contribution guide for Meta employees OR contribution guide.