Adapt SQL drivers to Qt 6 change of QVariant::isNull

In Qt 5, QVariant::isNull returned true if either the variant didn't
contain a value, or if the value was of a nullable type where the type's
isNull member function returned true.

In Qt 6, QVariant::isNull only returns true for variants that don't
contain a value; if the value contained is e.g. a null-QString or
QDateTime, then QVariant::isNull  returns false.

This change requires a follow up in the SQL drivers, which must
still treat null-values the same as null-variants, lest they write data
into the data base.

Add a static helper to QSqlResultPrivate that implements isNull-checking
of variants that contain a nullable type relevant for Sql, and add a
test case to the QSqlQuery test that exercises that code.

Pick-to: 6.2 6.3
Fixes: QTBUG-99408
Fixes: QTBUG-98471
Change-Id: I08b74a33aa3235c37d974f182da1f2bdcfd8217e
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/plugins/sqldrivers/sqlite/qsql_sqlite.cpp b/src/plugins/sqldrivers/sqlite/qsql_sqlite.cpp
index d13fb1787c..9f90d91e82 100644
--- a/src/plugins/sqldrivers/sqlite/qsql_sqlite.cpp
+++ b/src/plugins/sqldrivers/sqlite/qsql_sqlite.cpp
@@ -501,7 +501,7 @@ bool QSQLiteResult::exec()
             res = SQLITE_OK;
             const QVariant &value = values.at(i);
 
-            if (value.isNull()) {
+            if (QSqlResultPrivate::isVariantNull(value)) {
                 res = sqlite3_bind_null(d->stmt, i + 1);
             } else {
                 switch (value.userType()) {