Handle QCollator with locale C by delegating to QString

Previously, the C locale was treated as English because each back-end
takes the locale's bcp47Name(), which maps C to en. However, the C
locale has its own rules; which QString helpfully implements; so we
can delegate to it in this case. Extended this to sort keys, where
possible. Clean up existing implementations in the process.

Extended tst_QCollator::compare() with some cases to check this. That
required wrapping the test's calls to collator.compare() in a sign
canonicalizer, since it can return any -ve for < or +ve for >, not
just -1 and +1 for these cases (and it'd be rash to hard-code specific
negative and positive values, as they may vary between backends).

[ChangeLog][QtCore][QCollator] Added support for collation in the C
locale, albeit this is only well-defined for ASCII. Collation sort
keys remain unsupported on Darwin.

Fixes: QTBUG-58621
Change-Id: I327010d90f09bd1b1816f5590cb124e3d423e61d
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 13 insertions, 5 deletions

diff --git a/tests/auto/corelib/tools/qcollator/tst_qcollator.cpp b/tests/auto/corelib/tools/qcollator/tst_qcollator.cpp
index 2d65d3433f..72f88a235d 100644
--- a/tests/auto/corelib/tools/qcollator/tst_qcollator.cpp
+++ b/tests/auto/corelib/tools/qcollator/tst_qcollator.cpp
@@ -93,7 +93,7 @@ void tst_QCollator::compare_data()
     QTest::addColumn<int>("caseInsensitiveResult");
     QTest::addColumn<bool>("numericMode");
     QTest::addColumn<bool>("ignorePunctuation");
-    QTest::addColumn<int>("punctuationResult");
+    QTest::addColumn<int>("punctuationResult"); // Test ignores punctuation *and case*
 
     /*
         It's hard to test English, because it's treated differently
@@ -169,8 +169,12 @@ void tst_QCollator::compare_data()
     QTest::newRow("french6") << QString("fr_FR") << QString("Test 9") << QString("Test_19") << -1 << -1 << true << true << -1;
     QTest::newRow("french7") << QString("fr_FR") << QString("test_19") << QString("test 19") << 1 << 1 << true << false << 1;
     QTest::newRow("french8") << QString("fr_FR") << QString("test.19") << QString("test,19") << 1 << 1 << true << true << 0;
-}
 
+    // C locale: case sensitive [A-Z] < [a-z] but case insensitive [Aa] < [Bb] <...< [Zz]
+    const QString C = QStringLiteral("C");
+    QTest::newRow("C:ABBA:AaaA") << C << QStringLiteral("ABBA") << QStringLiteral("AaaA") << -1 << 1 << false << false << 1;
+    QTest::newRow("C:AZa:aAZ") << C << QStringLiteral("AZa") << QStringLiteral("aAZ") << -1 << 1 << false << false << 1;
+}
 
 void tst_QCollator::compare()
 {
@@ -184,6 +188,10 @@ void tst_QCollator::compare()
     QFETCH(int, punctuationResult);
 
     QCollator collator(locale);
+    // Need to canonicalize sign to -1, 0 or 1, as .compare() can produce any -ve for <, any +ve for >.
+    auto asSign = [](int compared) {
+        return compared < 0 ? -1 : compared > 0 ? 1 : 0;
+    };
 
 #if defined(Q_OS_ANDROID) && !defined(Q_OS_ANDROID_EMBEDDED)
     if (collator.locale() != QLocale())
@@ -193,12 +201,12 @@ void tst_QCollator::compare()
     if (numericMode)
         collator.setNumericMode(true);
 
-    QCOMPARE(collator.compare(s1, s2), result);
+    QCOMPARE(asSign(collator.compare(s1, s2)), result);
     collator.setCaseSensitivity(Qt::CaseInsensitive);
-    QCOMPARE(collator.compare(s1, s2), caseInsensitiveResult);
+    QCOMPARE(asSign(collator.compare(s1, s2)), caseInsensitiveResult);
 #if !QT_CONFIG(iconv)
     collator.setIgnorePunctuation(ignorePunctuation);
-    QCOMPARE(collator.compare(s1, s2), punctuationResult);
+    QCOMPARE(asSign(collator.compare(s1, s2)), punctuationResult);
 #endif
 }