Fix writeValueAtRange sending scalar for single-element range writes

OPC UA requires an array value when using an index range, even for a
single element.  Strict servers reject a scalar with BadIndexRangeNoData.
Wrap the coerced value in a QVariantList when it isn't one already.

1 files changed, 6 insertions, 0 deletions

diff --git a/src/OpcUaMonitoredNode.cpp b/src/OpcUaMonitoredNode.cpp
index 922ad43..c5f1dc0 100644
--- a/src/OpcUaMonitoredNode.cpp
+++ b/src/OpcUaMonitoredNode.cpp
@@ -568,6 +568,12 @@ OpcUaMonitoredNode::writeValueAtRange (const QVariant &value,
       return;
     }
 
+  // OPC UA requires an array value for index-range writes, even for a
+  // single element.  Wrap scalars in a one-element list so strict
+  // servers don't reject with BadIndexRangeNoData.
+  if (coerced.metaType ().id () != QMetaType::QVariantList)
+    coerced = QVariant::fromValue (QVariantList{ coerced });
+
   m_pendingRangeWrite = true;
 
   if (!m_node->writeAttributeRange (QOpcUa::NodeAttribute::Value, coerced,