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>

1 files changed, 24 insertions, 0 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;
+}