Revert "QTranslator: fix loading order when loading from locale"

This reverts commit 9a11273.

Reason for revert: The fix tried to find a sensible order if
the same language is listed multiple times in QLocale::uiLanguages().
Anyhow, it breaks for lists where entirely different languages are listed. This needs more thought.

Fixes: QTBUG-129434
Pick-to: 6.8 6.7 6.5
Change-Id: I8c074cbf1ddc2ddf223ec09aef38dfc1ef7fc85f
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
(cherry picked from commit f3fc7b2)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/corelib/kernel/qtranslator.cpp

@@ -638,41 +638,25 @@ static QString find_translation(const QLocale & locale,
             languages.insert(i + 1, lowerLang);
     }
 
-    QStringList candidates;
-    // assume 3 segments for each entry
-    candidates.reserve(languages.size() * 3);
-    for (QStringView language : std::as_const(languages)) {
-        // for each language, add versions without territory and script
+    for (QString localeName : std::as_const(languages)) {
+        // try the complete locale name first and progressively truncate from
+        // the end until a matching language tag is found (with or without suffix)
         for (;;) {
-            candidates += language.toString();
-            int rightmost = language.lastIndexOf(u'_');
-            if (rightmost <= 0)
-                break;
-            language.truncate(rightmost);
-        }
-    }
+            realname += localeName + suffixOrDotQM;
+            if (is_readable_file(realname))
+                return realname;
 
-    // now sort the list of candidates
-    std::sort(candidates.begin(), candidates.end(), [](const auto &lhs, const auto &rhs){
-        const auto rhsSegments = rhs.count(u'_');
-        const auto lhsSegments = lhs.count(u'_');
-        // candidates with more segments come first
-        if (rhsSegments != lhsSegments)
-            return rhsSegments < lhsSegments;
-        // candidates with same number of segments are sorted alphanumerically
-        return lhs < rhs;
-    });
-
-    for (const QString &localeName : std::as_const(candidates)) {
-        realname += localeName + suffixOrDotQM;
-        if (is_readable_file(realname))
-            return realname;
+            realname.truncate(realNameBaseSize + localeName.size());
+            if (is_readable_file(realname))
+                return realname;
 
-        realname.truncate(realNameBaseSize + localeName.size());
-        if (is_readable_file(realname))
-            return realname;
+            realname.truncate(realNameBaseSize);
 
-        realname.truncate(realNameBaseSize);
+            int rightmost = localeName.lastIndexOf(u'_');
+            if (rightmost <= 0)
+                break; // no truncations anymore, break
+            localeName.truncate(rightmost);
+        }
     }
 
     const int realNameBaseSizeFallbacks = path.size() + filename.size();

tests/auto/corelib/kernel/qtranslator/tst_qtranslator.cpp

@@ -27,7 +27,6 @@ private slots:
 
     void load_data();
     void load();
-    void loadLocale_data();
     void loadLocale();
     void threadLoad();
     void testLanguageChange();
@@ -117,23 +116,12 @@ void tst_QTranslator::load()
     }
 }
 
-void tst_QTranslator::loadLocale_data()
-{
-    QTest::addColumn<QString>("localeName");
-    QTest::addColumn<QStringList>("fileNames");
-
-    QTest::addRow("US English")
-                            << "en_US"
-                            << QStringList{"en_US.qm", "en_US", "en.qm", "en"};
-    QTest::addRow("Australia")
-                            << "en_AU"
-                            << QStringList{"en_Latn_AU.qm", "en_AU.qm", "en.qm"};
-}
-
 void tst_QTranslator::loadLocale()
 {
-    QFETCH(const QString, localeName);
-    QFETCH(const QStringList, fileNames);
+    QLocale locale;
+    auto localeName = locale.uiLanguages(QLocale::TagSeparator::Underscore).value(0);
+    if (localeName.isEmpty())
+        QSKIP("This test requires at least one available UI language.");
 
     QByteArray ba;
     {
@@ -146,16 +134,36 @@ void tst_QTranslator::loadLocale()
     QTemporaryDir dir;
     QVERIFY(dir.isValid());
 
-    const auto path = dir.path();
+    auto path = dir.path();
     QFile file(path + "/dummy");
     QVERIFY2(file.open(QFile::WriteOnly), qPrintable(file.errorString()));
     QCOMPARE(file.write(ba), ba.size());
     file.close();
 
+    /*
+        Test the following order:
+
+        /tmp/tmpDir/foo-en_US.qm
+        /tmp/tmpDir/foo-en_US
+        /tmp/tmpDir/foo-en.qm
+        /tmp/tmpDir/foo-en
+        /tmp/tmpDir/foo.qm
+        /tmp/tmpDir/foo-
+        /tmp/tmpDir/foo
+    */
+
     QStringList files;
-    for (const auto &fileName : fileNames) {
-        files.append(path + "/foo-" + fileName);
+    while (true) {
+        files.append(path + "/foo-" + localeName + ".qm");
+        QVERIFY2(file.copy(files.last()), qPrintable(file.errorString()));
+
+        files.append(path + "/foo-" + localeName);
         QVERIFY2(file.copy(files.last()), qPrintable(file.errorString()));
+
+        int rightmost = localeName.lastIndexOf(QLatin1Char('_'));
+        if (rightmost <= 0)
+            break;
+        localeName.truncate(rightmost);
     }
 
     files.append(path + "/foo.qm");
@@ -167,14 +175,10 @@ void tst_QTranslator::loadLocale()
     files.append(path + "/foo");
     QVERIFY2(file.rename(files.last()), qPrintable(file.errorString()));
 
-    QLocale locale(localeName);
     QTranslator tor;
     for (const auto &filePath : files) {
         QVERIFY(tor.load(locale, "foo", "-", path, ".qm"));
-        // As the file system might be case insensitive, we can't guarantee that
-        // the casing of the file name is preserved. The order of loading
-        // en_AU vs en_au if both exist is undefined anyway.
-        QCOMPARE(tor.filePath().toLower(), filePath.toLower());
+        QCOMPARE(tor.filePath(), filePath);
         QVERIFY2(file.remove(filePath), qPrintable(file.errorString()));
     }
 }