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>

3 files changed, 40 insertions, 5 deletions

diff --git a/src/imports/localstorage/plugin.cpp b/src/imports/localstorage/plugin.cpp
index b8d7030763..d32bb0069d 100644
--- a/src/imports/localstorage/plugin.cpp
+++ b/src/imports/localstorage/plugin.cpp
@@ -257,6 +257,15 @@ static ReturnedValue qmlsqldatabase_rows_item(CallContext *ctx)
     return qmlsqldatabase_rows_index(r, scope.engine, ctx->argc() ? ctx->args()[0].toUInt32() : 0);
 }
 
+static QVariant toSqlVariant(QV4::ExecutionEngine *engine, const QV4::ScopedValue &value)
+{
+    // toVariant() maps a null JS value to QVariant(VoidStar), but the SQL module
+    // expects a null variant. (this is because of QTBUG-40880)
+    if (value->isNull())
+        return QVariant();
+    return engine->toVariant(value, /*typehint*/-1);
+}
+
 static ReturnedValue qmlsqldatabase_executeSql(CallContext *ctx)
 {
     QV4::Scope scope(ctx);
@@ -287,8 +296,9 @@ static ReturnedValue qmlsqldatabase_executeSql(CallContext *ctx)
                 ScopedArrayObject array(scope, values);
                 quint32 size = array->getLength();
                 QV4::ScopedValue v(scope);
-                for (quint32 ii = 0; ii < size; ++ii)
-                    query.bindValue(ii, scope.engine->toVariant((v = array->getIndexed(ii)), -1));
+                for (quint32 ii = 0; ii < size; ++ii) {
+                    query.bindValue(ii, toSqlVariant(scope.engine, (v = array->getIndexed(ii))));
+                }
             } else if (values->as<Object>()) {
                 ScopedObject object(scope, values);
                 ObjectIterator it(scope, object, ObjectIterator::WithProtoChain|ObjectIterator::EnumerableOnly);
@@ -298,7 +308,7 @@ static ReturnedValue qmlsqldatabase_executeSql(CallContext *ctx)
                     key = it.nextPropertyName(val);
                     if (key->isNull())
                         break;
-                    QVariant v = scope.engine->toVariant(val, -1);
+                    QVariant v = toSqlVariant(scope.engine, val);
                     if (key->isString()) {
                         query.bindValue(key->stringValue()->toQString(), v);
                     } else {
@@ -307,7 +317,7 @@ static ReturnedValue qmlsqldatabase_executeSql(CallContext *ctx)
                     }
                 }
             } else {
-                query.bindValue(0, scope.engine->toVariant(values, -1));
+                query.bindValue(0, toSqlVariant(scope.engine, values));
             }
         }
         if (query.exec()) {
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.