Null pointer exception when reading a complex type with empty arrays. (#2798) (#2799)

The server under test has a extension object with a complex type.  Type id = {nsu=http://opcfoundation.org/UA/Machinery/Result/;i=5008}.  This contains something with a variant array that is null though (-1).  SetProperty should support setting a Array that is null.  Therefore, test for null collection (case when length was encoded as -1) before dereferencing ahead of the ToArrray() conversion to Array.

Co-authored-by: Marc Schier <marcschier@users.noreply.github.com>

Author: mregen

Stack/Opc.Ua.Core/Types/Encoders/BinaryDecoder.cs

@@ -1386,15 +1386,15 @@ public Array ReadArray(
                 switch (builtInType)
                 {
                     case BuiltInType.Boolean:
-                        return ReadBooleanArray(fieldName).ToArray();
+                        return ReadBooleanArray(fieldName)?.ToArray();
                     case BuiltInType.SByte:
-                        return ReadSByteArray(fieldName).ToArray();
+                        return ReadSByteArray(fieldName)?.ToArray();
                     case BuiltInType.Byte:
-                        return ReadByteArray(fieldName).ToArray();
+                        return ReadByteArray(fieldName)?.ToArray();
                     case BuiltInType.Int16:
-                        return ReadInt16Array(fieldName).ToArray();
+                        return ReadInt16Array(fieldName)?.ToArray();
                     case BuiltInType.UInt16:
-                        return ReadUInt16Array(fieldName).ToArray();
+                        return ReadUInt16Array(fieldName)?.ToArray();
                     case BuiltInType.Enumeration:
                     {
                         DetermineIEncodeableSystemType(ref systemType, encodeableTypeId);
@@ -1406,51 +1406,51 @@ public Array ReadArray(
                         goto case BuiltInType.Int32;
                     }
                     case BuiltInType.Int32:
-                        return ReadInt32Array(fieldName).ToArray();
+                        return ReadInt32Array(fieldName)?.ToArray();
                     case BuiltInType.UInt32:
-                        return ReadUInt32Array(fieldName).ToArray();
+                        return ReadUInt32Array(fieldName)?.ToArray();
                     case BuiltInType.Int64:
-                        return ReadInt64Array(fieldName).ToArray();
+                        return ReadInt64Array(fieldName)?.ToArray();
                     case BuiltInType.UInt64:
-                        return ReadUInt64Array(fieldName).ToArray();
+                        return ReadUInt64Array(fieldName)?.ToArray();
                     case BuiltInType.Float:
-                        return ReadFloatArray(fieldName).ToArray();
+                        return ReadFloatArray(fieldName)?.ToArray();
                     case BuiltInType.Double:
-                        return ReadDoubleArray(fieldName).ToArray();
+                        return ReadDoubleArray(fieldName)?.ToArray();
                     case BuiltInType.String:
-                        return ReadStringArray(fieldName).ToArray();
+                        return ReadStringArray(fieldName)?.ToArray();
                     case BuiltInType.DateTime:
-                        return ReadDateTimeArray(fieldName).ToArray();
+                        return ReadDateTimeArray(fieldName)?.ToArray();
                     case BuiltInType.Guid:
-                        return ReadGuidArray(fieldName).ToArray();
+                        return ReadGuidArray(fieldName)?.ToArray();
                     case BuiltInType.ByteString:
-                        return ReadByteStringArray(fieldName).ToArray();
+                        return ReadByteStringArray(fieldName)?.ToArray();
                     case BuiltInType.XmlElement:
-                        return ReadXmlElementArray(fieldName).ToArray();
+                        return ReadXmlElementArray(fieldName)?.ToArray();
                     case BuiltInType.NodeId:
-                        return ReadNodeIdArray(fieldName).ToArray();
+                        return ReadNodeIdArray(fieldName)?.ToArray();
                     case BuiltInType.ExpandedNodeId:
-                        return ReadExpandedNodeIdArray(fieldName).ToArray();
+                        return ReadExpandedNodeIdArray(fieldName)?.ToArray();
                     case BuiltInType.StatusCode:
-                        return ReadStatusCodeArray(fieldName).ToArray();
+                        return ReadStatusCodeArray(fieldName)?.ToArray();
                     case BuiltInType.QualifiedName:
-                        return ReadQualifiedNameArray(fieldName).ToArray();
+                        return ReadQualifiedNameArray(fieldName)?.ToArray();
                     case BuiltInType.LocalizedText:
-                        return ReadLocalizedTextArray(fieldName).ToArray();
+                        return ReadLocalizedTextArray(fieldName)?.ToArray();
                     case BuiltInType.DataValue:
-                        return ReadDataValueArray(fieldName).ToArray();
+                        return ReadDataValueArray(fieldName)?.ToArray();
                     case BuiltInType.Variant:
                     {
                         if (DetermineIEncodeableSystemType(ref systemType, encodeableTypeId))
                         {
                             return ReadEncodeableArray(fieldName, systemType, encodeableTypeId);
                         }
-                        return ReadVariantArray(fieldName).ToArray();
+                        return ReadVariantArray(fieldName)?.ToArray();
                     }
                     case BuiltInType.ExtensionObject:
-                        return ReadExtensionObjectArray(fieldName).ToArray();
+                        return ReadExtensionObjectArray(fieldName)?.ToArray();
                     case BuiltInType.DiagnosticInfo:
-                        return ReadDiagnosticInfoArray(fieldName).ToArray();
+                        return ReadDiagnosticInfoArray(fieldName)?.ToArray();
                     default:
                     {
                         if (DetermineIEncodeableSystemType(ref systemType, encodeableTypeId))
@@ -1604,7 +1604,7 @@ private bool DetermineIEncodeableSystemType(ref Type systemType, ExpandedNodeId
         }
 
         /// <summary>
-        /// Reads and returns an array of elements of the specified length and builtInType 
+        /// Reads and returns an array of elements of the specified length and builtInType
         /// </summary>
         private Array ReadArrayElements(int length, BuiltInType builtInType)
         {