QLocale: Allow direct conversion from language, country, and script codes

This complements patch a148c7b5d71d244, where languageToCode(),
countryToCode() scriptToCode() methods were introduced, with matching
codeToLanguage(), codeToCountry(), and codeToScript() methods.

This allows us to remove the use of private Qt Core API in Qt Linguist.

[ChangeLog][QtCore][QLocale] Added static codeToLanguage(),
codeToCountry(), codeToScript() methods that convert ISO code strings
to the respective enum values.

Change-Id: If5c0843a718c006ade086a6f74ceb86ac6e0fce4
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

src/corelib/text/qlocale.cpp

@@ -102,7 +102,7 @@ QLocale::Language QLocalePrivate::codeToLanguage(QStringView code) noexcept
 {
     const auto len = code.size();
     if (len != 2 && len != 3)
-        return QLocale::C;
+        return QLocale::AnyLanguage;
     char16_t uc1 = code[0].toLower().unicode();
     char16_t uc2 = code[1].toLower().unicode();
     char16_t uc3 = len > 2 ? code[2].toLower().unicode() : 0;
@@ -131,7 +131,7 @@ QLocale::Language QLocalePrivate::codeToLanguage(QStringView code) noexcept
         if (uc1 == 'j' && uc2 == 'i') // ji -> yi
             return QLocale::Yiddish;
     }
-    return QLocale::C;
+    return QLocale::AnyLanguage;
 }
 
 QLocale::Script QLocalePrivate::codeToScript(QStringView code) noexcept
@@ -574,8 +574,8 @@ QLocaleId QLocaleId::fromName(const QString &name)
         return { QLocale::C, 0, 0 };
 
     QLocale::Language langId = QLocalePrivate::codeToLanguage(lang);
-    if (langId == QLocale::C)
+    if (langId == QLocale::AnyLanguage)
-        return QLocaleId { langId, 0, 0 };
+        return { QLocale::C, 0, 0 };
     return { langId, QLocalePrivate::codeToScript(script), QLocalePrivate::codeToCountry(land) };
 }
 
@@ -1353,13 +1353,27 @@ QString QLocale::bcp47Name() const
     For \c QLocale::AnyLanguage an empty string is returned.
 
     \since 6.1
-    \sa language(), name(), bcp47Name(), countryToCode(), scriptToCode()
+    \sa codeToLanguage(), language(), name(), bcp47Name(), countryToCode(), scriptToCode()
 */
 QString QLocale::languageToCode(Language language)
 {
     return QLocalePrivate::languageToCode(language);
 }
 
+/*!
+    Returns the QLocale::Language enum corresponding to the two- or three-letter
+    \a languageCode, as defined in the ISO 639 standards.
+
+    If the code is invalid or not known QLocale::AnyLanguage is returned.
+
+    \since 6.1
+    \sa languageToCode(), codeToCountry(), codeToScript()
+*/
+QLocale::Language QLocale::codeToLanguage(QStringView languageCode) noexcept
+{
+    return QLocalePrivate::codeToLanguage(languageCode);
+}
+
 /*!
     Returns the two-letter country code for \a country, as defined
     in the ISO 3166 standard.
@@ -1367,13 +1381,27 @@ QString QLocale::languageToCode(Language language)
     \note For \c{QLocale::AnyCountry} an empty string is returned.
 
     \since 6.1
-    \sa country(), name(), bcp47Name(), languageToCode(), scriptToCode()
+    \sa codeToCountry(), country(), name(), bcp47Name(), languageToCode(), scriptToCode()
 */
 QString QLocale::countryToCode(Country country)
 {
     return QLocalePrivate::countryToCode(country);
 }
 
+/*!
+    Returns the QLocale::Country enum corresponding to the two-letter or
+    three-digit \a countryCode, as defined in the ISO 3166 standard.
+
+    If the code is invalid or not known QLocale::AnyCountry is returned.
+
+    \since 6.1
+    \sa countryToCode(), codeToLanguage(), codeToScript()
+*/
+QLocale::Country QLocale::codeToCountry(QStringView countryCode) noexcept
+{
+    return QLocalePrivate::codeToCountry(countryCode);
+}
+
 /*!
     Returns the four-letter script code for \a script, as defined in the
     ISO 15924 standard.
@@ -1388,6 +1416,20 @@ QString QLocale::scriptToCode(Script script)
     return QLocalePrivate::scriptToCode(script);
 }
 
+/*!
+    Returns the QLocale::Script enum corresponding to the four-letter script
+    \a scriptCode, as defined in the ISO 15924 standard.
+
+    If the code is invalid or not known QLocale::AnyScript is returned.
+
+    \since 6.1
+    \sa scriptToCode(), codeToLanguage(), codeToCountry()
+*/
+QLocale::Script QLocale::codeToScript(QStringView scriptCode) noexcept
+{
+    return QLocalePrivate::codeToScript(scriptCode);
+}
+
 /*!
     Returns a QString containing the name of \a language.
 

src/corelib/text/qlocale.h

@@ -1068,8 +1068,11 @@ public:
     QStringList uiLanguages() const;
 
     static QString languageToCode(Language language);
+    static Language codeToLanguage(QStringView languageCode) noexcept;
     static QString countryToCode(Country country);
+    static Country codeToCountry(QStringView countryCode) noexcept;
     static QString scriptToCode(Script script);
+    static Script codeToScript(QStringView scriptCode) noexcept;
 
     static QString languageToString(Language language);
     static QString countryToString(Country country);

src/corelib/text/qlocale_p.h

@@ -148,7 +148,6 @@ namespace QIcu {
 
 struct QLocaleId
 {
-    // ### Also used by Translator::languageAndCountry() in qttools:
     Q_CORE_EXPORT static QLocaleId fromName(const QString &name);
     inline bool operator==(QLocaleId other) const
     { return language_id == other.language_id && script_id == other.script_id && country_id == other.country_id; }

tests/auto/corelib/text/qlocale/tst_qlocale.cpp

@@ -151,6 +151,7 @@ private slots:
     void numberFormatChakma();
 
     void lcsToCode();
+    void codeToLcs();
 
     // *** ORDER-DEPENDENCY *** (This Is Bad.)
     // Test order is determined by order of declaration here: *all* tests that
@@ -3240,5 +3241,31 @@ void tst_QLocale::lcsToCode()
     QCOMPARE(QLocale::scriptToCode(QLocale::SimplifiedHanScript), QString("Hans"));
 }
 
+void tst_QLocale::codeToLcs()
+{
+    QCOMPARE(QLocale::codeToLanguage(QString()), QLocale::AnyLanguage);
+    QCOMPARE(QLocale::codeToLanguage(QString(" ")), QLocale::AnyLanguage);
+    QCOMPARE(QLocale::codeToLanguage(QString("und")), QLocale::AnyLanguage);
+    QCOMPARE(QLocale::codeToLanguage(QString("e")), QLocale::AnyLanguage);
+    QCOMPARE(QLocale::codeToLanguage(QString("en")), QLocale::English);
+    QCOMPARE(QLocale::codeToLanguage(QString("EN")), QLocale::English);
+    QCOMPARE(QLocale::codeToLanguage(QString("eng")), QLocale::AnyLanguage);
+    QCOMPARE(QLocale::codeToLanguage(QString("ha")), QLocale::Hausa);
+    QCOMPARE(QLocale::codeToLanguage(QString("haw")), QLocale::Hawaiian);
+
+    QCOMPARE(QLocale::codeToCountry(QString()), QLocale::AnyCountry);
+    QCOMPARE(QLocale::codeToCountry(QString("ZZ")), QLocale::AnyCountry);
+    QCOMPARE(QLocale::codeToCountry(QString("US")), QLocale::UnitedStates);
+    QCOMPARE(QLocale::codeToCountry(QString("us")), QLocale::UnitedStates);
+    QCOMPARE(QLocale::codeToCountry(QString("USA")), QLocale::AnyCountry);
+    QCOMPARE(QLocale::codeToCountry(QString("EU")), QLocale::EuropeanUnion);
+    QCOMPARE(QLocale::codeToCountry(QString("001")), QLocale::World);
+    QCOMPARE(QLocale::codeToCountry(QString("150")), QLocale::Europe);
+
+    QCOMPARE(QLocale::codeToScript(QString()), QLocale::AnyScript);
+    QCOMPARE(QLocale::codeToScript(QString("Zzzz")), QLocale::AnyScript);
+    QCOMPARE(QLocale::codeToScript(QString("Hans")), QLocale::SimplifiedHanScript);
+}
+
 QTEST_MAIN(tst_QLocale)
 #include "tst_qlocale.moc"