VPN-6622: Fix broken device language for Chinese (#9933) (#9968)

* VPN-6622 fix for iOS

* make it generalizable to help with Android

* make it generalizable to help with Android

* better iOS explanation

* make linter happy

* update tests, improve logic for non-iOS

src/localizer.cpp

@@ -77,6 +77,14 @@ QList<QPair<QString, QString>> Localizer::parseBCP47Languages(
       continue;
     }
 
+    // Chinese is often reported as `zh-Hant-HK`, and we want the middle
+    // section.
+    QString script = parts[1];
+    if (script == "Hans" || script == "Hant") {
+      codes.append(QPair<QString, QString>{parts[0], script});
+      continue;
+    }
+
     QString country = parts.last();
     if (country.length() == 2) {
       codes.append(QPair<QString, QString>{parts[0], country});
@@ -96,11 +104,23 @@ QList<QPair<QString, QString>> Localizer::parseIOSLanguages(
   QList<QPair<QString, QString>> codes;
 
   for (const QString& language : languages) {
-    // By documentation, the language code should be in the format
-    // <language>-<script>_<country>. And we don't care about the script.
+    // The language code comes in the format <language>-<country> or
+    // <language>-<script>-<country>.
+    // For an iOS device set to these 6 languages: Chinese Traditional (Macao),
+    // Chinese Traditional, Chinese Simplified, English, Mexican Spanish,
+    // Spanish
+    // ...we get these language codes:
+    // [zh-Hant-MO,zh-Hant-US,zh-Hans-US,en-US,es-MX,es-US]
+    // iOS shows the 2 part versions for nearly all languages, and shows the
+    // 3 part version only when there is a script - like for Chinese variants.
+    // Thus, we can pull the second chunk of the locale string in all cases to
+    // get the translations flow required by our app. That second chunk gives
+    // the country for all languages except Chinese, where it gives the script -
+    // and in both these situations, this is what we want (script for Chinese,
+    // country for all others).
     QString countryCode;
 
-    QStringList parts = language.split('_');
+    QStringList parts = language.split('-');
     if (parts.length() > 1) {
       countryCode = parts[1];
     }
@@ -125,8 +145,27 @@ QString Localizer::systemLanguageCode() const {
 #endif
 
   for (const QPair<QString, QString>& language : uiLanguages) {
-    QString selectedLanguage =
-        findLanguageCode(language.first, language.second);
+    QString languagePart = language.first;
+    QString localePart = language.second;
+
+    // iOS reports Chinese as "zh-Hans" and "zh-Hant". Android reports
+    // them as "zh-CN" and "zh-Hans". However the app uses "zh-CN" and
+    // "zh-TW". We need to manually adjust these. More info:
+    // https://stackoverflow.com/questions/4892372/language-codes-for-simplified-chinese-and-traditional-chinese
+    // (For country-specific variants, it reports it as "zh-Hant-MO", etc. Since
+    // the app only looks at the strings before the 1st and 2nd dashes, we
+    // ignore the country - which is what we want to do, as we don't have
+    // translations for Chinese beyond simplified and traditional.)
+    if (languagePart == "zh") {
+      if (localePart == "Hans") {
+        localePart = "CN";
+      }
+      if (localePart == "Hant") {
+        localePart = "TW";
+      }
+    }
+
+    QString selectedLanguage = findLanguageCode(languagePart, localePart);
     if (!selectedLanguage.isEmpty()) {
       return selectedLanguage;
     }

tests/unit_tests/testlocalizer.cpp

@@ -158,17 +158,17 @@ void TestLocalizer::parseIOSLanguages_data() {
   {
     LanguageList a;
     a.append(QPair<QString, QString>{"aa", "bb"});
-    QTest::addRow("language_country") << QStringList("aa_bb") << a;
+    QTest::addRow("language-country") << QStringList("aa-bb") << a;
   }
   {
     LanguageList a;
-    a.append(QPair<QString, QString>{"aa", ""});
+    a.append(QPair<QString, QString>{"aa", "cc"});
     QTest::addRow("language-script") << QStringList("aa-cc") << a;
   }
   {
     LanguageList a;
-    a.append(QPair<QString, QString>{"aa", "bb"});
-    QTest::addRow("language-script_country") << QStringList("aa-cc_bb") << a;
+    a.append(QPair<QString, QString>{"aa", "cc"});
+    QTest::addRow("language-script-country") << QStringList("aa-cc-bb") << a;
   }
 }