Fix bug in SQL database integration with null values

Since commit 91d6a63ab317817990c3b2306860adbd8916cca4 a null JS value is
mapped to a QVariant(VoidStar) to properly create null JS values when
converting back again. However that broke the binding of values in the SQL
database, where it ended up mapping null to an empty string.

[ChangeLog][QtQml] Fix mapping of null JS values to null SQL values instead
of empty strings.

Task-number: QTBUG-53412
Change-Id: Icf1fea4674e9dd8bb5313e3770ed2d3f99849987
Reviewed-by: Robin Burchell <robin.burchell@viroteck.net>

2 files changed, 26 insertions, 1 deletions

diff --git a/tests/auto/qml/qqmlsqldatabase/data/nullvalues.js b/tests/auto/qml/qqmlsqldatabase/data/nullvalues.js
new file mode 100644
index 0000000000..322a7aea03
--- /dev/null
+++ b/tests/auto/qml/qqmlsqldatabase/data/nullvalues.js
@@ -0,0 +1,24 @@
+.import QtQuick.LocalStorage 2.0 as Sql
+
+function test() {
+    var db = Sql.LocalStorage.openDatabaseSync("QmlTestDB-nullvalues", "", "Test database from Qt autotests", 1000000);
+    var r="transaction_not_finished";
+
+    db.transaction(
+        function(tx) {
+            tx.executeSql('CREATE TABLE IF NOT EXISTS NullValues(salutation TEXT, salutee TEXT)');
+            tx.executeSql('INSERT INTO NullValues VALUES(?, ?)', [ 'hello', null ]);
+            var firstRow = tx.executeSql("SELECT * FROM NullValues").rows.item(0);
+            if (firstRow.salutation !== "hello")
+               return
+            if (firstRow.salutee === "") {
+                r = "wrong_data_type"
+                return
+            }
+            if (firstRow.salutee === null)
+                r = "passed";
+        }
+    );
+
+    return r;
+}
diff --git a/tests/auto/qml/qqmlsqldatabase/tst_qqmlsqldatabase.cpp b/tests/auto/qml/qqmlsqldatabase/tst_qqmlsqldatabase.cpp
index b5b77ad10b..debafa3fe4 100644
--- a/tests/auto/qml/qqmlsqldatabase/tst_qqmlsqldatabase.cpp
+++ b/tests/auto/qml/qqmlsqldatabase/tst_qqmlsqldatabase.cpp
@@ -127,7 +127,7 @@ void tst_qqmlsqldatabase::checkDatabasePath()
     QVERIFY(engine->offlineStoragePath().contains("OfflineStorage"));
 }
 
-static const int total_databases_created_by_tests = 12;
+static const int total_databases_created_by_tests = 13;
 void tst_qqmlsqldatabase::testQml_data()
 {
     QTest::addColumn<QString>("jsfile"); // The input file
@@ -149,6 +149,7 @@ void tst_qqmlsqldatabase::testQml_data()
     QTest::newRow("error-outsidetransaction") << "error-outsidetransaction.js"; // reuse above
     QTest::newRow("reopen1") << "reopen1.js";
     QTest::newRow("reopen2") << "reopen2.js"; // re-uses above DB
+    QTest::newRow("null-values") << "nullvalues.js";
 
     // If you add a test, you should usually use a new database in the
     // test - in which case increment total_databases_created_by_tests above.