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 <[email protected]>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/plugins/sqldrivers/db2/qsql_db2.cpp b/src/plugins/sqldrivers/db2/qsql_db2.cpp
index e605ac91a20..00bcc1cc4aa 100644
--- a/src/plugins/sqldrivers/db2/qsql_db2.cpp
+++ b/src/plugins/sqldrivers/db2/qsql_db2.cpp
@@ -697,7 +697,7 @@ bool QDB2Result::exec()
     for (i = 0; i < values.count(); ++i) {
         // bind parameters - only positional binding allowed
         SQLLEN *ind = &indicators[i];
-        if (values.at(i).isNull())
+        if (QSqlResultPrivate::isVariantNull(values.at(i)))
             *ind = SQL_NULL_DATA;
         if (bindValueType(i) & QSql::Out)
             values[i].detach();