STR: * Set android system locale to zh-TW; * Kill firefox process and launch; * Observe UI locale in option menu and Settings ER: * UI display in zh-TW AR: * UI display in zh-CN UI will be correct if user switched system locale, and it can be reproduced when process killed, cold start;

Peter, could you comment on what you saw on your phone? This is pretty severe and I think we should fix it sooner or later. Thanks!

From what I observe, Fennec displays in zh-CN when 繁體中文（台灣） has a higher order than 中文（台灣）in android locale preference. However if 中文（台灣） is more preferred, UI will display in zh-TW without problem. Moreover, it seems that it's only possible to set 中文（台灣）in the first run UI, or being migrated from older android versions; if I remove that preference I'm unable to re-add it back, 繁體中文（台灣） still exists though. I also noticed that when this bug happens, about: page in Fennec as well as some UI messages still displays in English, a normal zh-CN build should have these messages localized. Other Information: Device: Google Nexus 5X Android Version: 7.1.2 (N2G47O) Fennec Version: 53.0.2

Just fyr for in case someone reading this bug do not read localized locale names: 繁體中文（台灣） literally is Traditional Chinese (Taiwan), and 中文（台灣） is Chinese (Taiwan). I suspect 繁體中文（台灣） is zh-Hant-TW, and 中文（台灣）should be zh-TW, but unfortunately I do not have android development environment in handy to confirm.

Too late to fix this in 53, but if 54 is affected, we might still be able to fix the issue for 54 in a dot release. We need to know if we still see the issue in 54 and 55. Escalating to Joe and Tim since this may be a serious issue for Fennec, and if so, we should put resources into fixing it as soon as we can.

Comment on attachment 8875665 [details] Bug 1369281 - Simplify Locale setting string without variant/script which is from Locale.toString(), https://reviewboard.mozilla.org/r/147088/#review151250 LGTM

Pushed by max@mxli.us: https://hg.mozilla.org/integration/autoland/rev/b977e23d261c Simplify Locale setting string without variant/script which is from Locale.toString(), r=nechen

Talked to Max offline and he landed the patch. Thanks :)

Please remember to ask for uplift.

Comment on attachment 8875665 [details] Bug 1369281 - Simplify Locale setting string without variant/script which is from Locale.toString(), Approval Request Comment [Feature/Bug causing the regression]: RTL Locale Switcher. [User impact if declined]: Cold launch will cause UI fallback to language default without country specific. zh_TW_#Hant -> zh(fallback zh_CN) [Is this code covered by automated tests?]: No [Has the fix been verified in Nightly?]: Yes [Needs manual test from QE? If yes, steps to reproduce]: STR: Switch system locale to zh_TW and force stop fennec, launch fennec and check UI. ER: UI display in zh_TW, not zh_CN [List of other uplifts needed for the feature/fix]: N/A [Is the change risky?]: No [Why is the change risky/not risky?]: Serialize locale to string manually with a simplified language_country format. [String changes made/needed]: No

Comment on attachment 8875665 [details] Bug 1369281 - Simplify Locale setting string without variant/script which is from Locale.toString(), beta is going to be 55 later today. Updating the request.

Looks like this missed landing for 54. If we do a dot release, we may want to take this patch.

Verified on Beta 55.0b1, that switching the Android system language to zh-TW 中文（台灣) displays the same language as installing the single locale build from archive http://archive.mozilla.org/pub/mobile/candidates/55.0b1-candidates/build2/android-api-15/zh-TW/. In previous Beta 54, the about:firefox and app settings were displayed in English as it was said in comment 2. This isn't reproducible anymore. Verified as fixed. Device: -Motorola Nexus 6 (Android 7.0)

Comment on attachment 8875665 [details] Bug 1369281 - Simplify Locale setting string without variant/script which is from Locale.toString(), Locale fix, we should definitely take this for beta 55.

Comment on attachment 8875665 [details] Bug 1369281 - Simplify Locale setting string without variant/script which is from Locale.toString(), My mistake, I was reviewing beta uplift requests in another window, and somehow missed this was for release. Leaving this for gchang to review.

Comment on attachment 8875665 [details] Bug 1369281 - Simplify Locale setting string without variant/script which is from Locale.toString(), Locale fix. We're gonna take this one in 54.0.1.

Devices: - Nexus 5 (Android 6.0.1); - LG G4 (Android 6.0); -Asus ZenPad 8.0 Z380KL (Android 6.0.1); Build: - 54.0.1 Hello, I've verified this using multiple devices and the issue was no longer reproducible. Marking as verified.