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>

7 files changed, 10 insertions, 10 deletions

diff --git a/src/plugins/sqldrivers/db2/qsql_db2.cpp b/src/plugins/sqldrivers/db2/qsql_db2.cpp
index e605ac91a2..00bcc1cc4a 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();
diff --git a/src/plugins/sqldrivers/ibase/qsql_ibase.cpp b/src/plugins/sqldrivers/ibase/qsql_ibase.cpp
index ba820a4416..d8cb3ae5f3 100644
--- a/src/plugins/sqldrivers/ibase/qsql_ibase.cpp
+++ b/src/plugins/sqldrivers/ibase/qsql_ibase.cpp
@@ -968,7 +968,7 @@ bool QIBaseResult::exec()
     setAt(QSql::BeforeFirstRow);
 
     if (d->inda) {
-        QList<QVariant>& values = boundValues();
+        const QList<QVariant> &values = boundValues();
         int i;
         if (values.count() > d->inda->sqld) {
             qWarning() << QLatin1String("QIBaseResult::exec: Parameter mismatch, expected") <<
@@ -984,7 +984,7 @@ bool QIBaseResult::exec()
                 continue;
             const QVariant val(values[i]);
             if (d->inda->sqlvar[para].sqltype & 1) {
-                if (val.isNull()) {
+                if (QSqlResultPrivate::isVariantNull(val)) {
                     // set null indicator
                     *(d->inda->sqlvar[para].sqlind) = -1;
                     // and set the value to 0, otherwise it would count as empty string.
diff --git a/src/plugins/sqldrivers/mysql/qsql_mysql.cpp b/src/plugins/sqldrivers/mysql/qsql_mysql.cpp
index caf406da46..837805cc46 100644
--- a/src/plugins/sqldrivers/mysql/qsql_mysql.cpp
+++ b/src/plugins/sqldrivers/mysql/qsql_mysql.cpp
@@ -929,7 +929,7 @@ bool QMYSQLResult::exec()
 
             MYSQL_BIND* currBind = &d->outBinds[i];
 
-            nullVector[i] = static_cast<my_bool>(val.isNull());
+            nullVector[i] = static_cast<my_bool>(QSqlResultPrivate::isVariantNull(val));
             currBind->is_null = &nullVector[i];
             currBind->length = 0;
             currBind->is_unsigned = 0;
diff --git a/src/plugins/sqldrivers/oci/qsql_oci.cpp b/src/plugins/sqldrivers/oci/qsql_oci.cpp
index 5ba862f430..324e502f8c 100644
--- a/src/plugins/sqldrivers/oci/qsql_oci.cpp
+++ b/src/plugins/sqldrivers/oci/qsql_oci.cpp
@@ -515,7 +515,7 @@ int QOCIResultPrivate::bindValues(QVariantList &values, IndicatorArray &indicato
 
         OCIBind * hbnd = nullptr; // Oracle handles these automatically
         sb2 *indPtr = &indicators[i];
-        *indPtr = val.isNull() ? -1 : 0;
+        *indPtr = QSqlResultPrivate::isVariantNull(val) ? -1 : 0;
 
         bindValue(sql, &hbnd, err, i, val, indPtr, &tmpSizes[i], tmpStorage);
     }
@@ -1372,7 +1372,7 @@ bool QOCICols::execBatch(QOCIResultPrivate *d, QVariantList &boundValues, bool a
             // not a list - create a deep-copy of the single value
             QOCIBatchColumn &singleCol = columns[i];
             singleCol.indicators = new sb2[1];
-            *singleCol.indicators = boundValues.at(i).isNull() ? -1 : 0;
+            *singleCol.indicators = QSqlResultPrivate::isVariantNull(boundValues.at(i)) ? -1 : 0;
 
             r = d->bindValue(d->sql, &singleCol.bindh, d->err, i,
                              boundValues.at(i), singleCol.indicators, &tmpSizes[i], tmpStorage);
@@ -1469,7 +1469,7 @@ bool QOCICols::execBatch(QOCIResultPrivate *d, QVariantList &boundValues, bool a
         for (uint row = 0; row < col.recordCount; ++row) {
             const QVariant &val = boundValues.at(i).toList().at(row);
 
-            if (val.isNull() && !d->isOutValue(i)) {
+            if (QSqlResultPrivate::isVariantNull(val) && !d->isOutValue(i)) {
                 columns[i].indicators[row] = -1;
                 columns[i].lengths[row] = 0;
             } else {
diff --git a/src/plugins/sqldrivers/odbc/qsql_odbc.cpp b/src/plugins/sqldrivers/odbc/qsql_odbc.cpp
index 1b3a55d096..dbbf984fa9 100644
--- a/src/plugins/sqldrivers/odbc/qsql_odbc.cpp
+++ b/src/plugins/sqldrivers/odbc/qsql_odbc.cpp
@@ -1419,7 +1419,7 @@ bool QODBCResult::exec()
             values[i].detach();
         const QVariant &val = values.at(i);
         SQLLEN *ind = &indicators[i];
-        if (val.isNull())
+        if (QSqlResultPrivate::isVariantNull(val))
             *ind = SQL_NULL_DATA;
         switch (val.typeId()) {
             case QMetaType::QDate: {
diff --git a/src/plugins/sqldrivers/psql/qsql_psql.cpp b/src/plugins/sqldrivers/psql/qsql_psql.cpp
index 4c3d6ca13f..07cc29d78c 100644
--- a/src/plugins/sqldrivers/psql/qsql_psql.cpp
+++ b/src/plugins/sqldrivers/psql/qsql_psql.cpp
@@ -856,7 +856,7 @@ static QString qCreateParamString(const QList<QVariant> &boundValues, const QSql
     QSqlField f;
     for (const QVariant &val : boundValues) {
         f.setMetaType(val.metaType());
-        if (val.isNull())
+        if (QSqlResultPrivate::isVariantNull(val))
             f.clear();
         else
             f.setValue(val);
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()) {