Fix XML Encoding and decoding of Matrix Element in Variant to conform to spec (#3053) (#3054)

* Fix XML Encoding and decoding to conform to spec

* fix test on linux

* fix typo

* Add missing DataValue & DiagnosticInfo Array Types

Co-authored-by: romanett <romanett98@gmail.com>

Author: mrsuciu

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

@@ -2740,15 +2740,15 @@ private Matrix ReadMatrix(string fieldName)
                 {
                     PushNamespace(Namespaces.OpcUaXsd);
 
+                    dimensions = ReadInt32Array("Dimensions");
+
                     if (BeginField("Elements", true))
                     {
-                        object contents = ReadVariantContents(out typeInfo);
-                        elements = contents as Array;
+                        typeInfo = MapElementTypeToTypeInfo(m_reader.LocalName);
+                        elements = ReadArray(null, typeInfo.ValueRank, typeInfo.BuiltInType, null);
                         EndField("Elements");
                     }
 
-                    dimensions = ReadInt32Array("Dimensions");
-
                     PopNamespace();
 
                     EndField(fieldName);
@@ -2782,6 +2782,43 @@ private Matrix ReadMatrix(string fieldName)
             }
         }
 
+        /// <summary>
+        /// Maps an element type name to its corresponding TypeInfo.Arrays value.
+        /// </summary>
+        /// <param name="elementTypeName">The name of the element type.</param>
+        /// <returns>The corresponding TypeInfo.Arrays value.</returns>
+        private TypeInfo MapElementTypeToTypeInfo(string elementTypeName)
+        {
+            return elementTypeName switch {
+                "Boolean" => TypeInfo.Arrays.Boolean,
+                "SByte" => TypeInfo.Arrays.SByte,
+                "Byte" => TypeInfo.Arrays.Byte,
+                "Int16" => TypeInfo.Arrays.Int16,
+                "UInt16" => TypeInfo.Arrays.UInt16,
+                "Int32" => TypeInfo.Arrays.Int32,
+                "UInt32" => TypeInfo.Arrays.UInt32,
+                "Int64" => TypeInfo.Arrays.Int64,
+                "UInt64" => TypeInfo.Arrays.UInt64,
+                "Float" => TypeInfo.Arrays.Float,
+                "Double" => TypeInfo.Arrays.Double,
+                "String" => TypeInfo.Arrays.String,
+                "DateTime" => TypeInfo.Arrays.DateTime,
+                "Guid" => TypeInfo.Arrays.Guid,
+                "ByteString" => TypeInfo.Arrays.ByteString,
+                "XmlElement" => TypeInfo.Arrays.XmlElement,
+                "NodeId" => TypeInfo.Arrays.NodeId,
+                "ExpandedNodeId" => TypeInfo.Arrays.ExpandedNodeId,
+                "StatusCode" => TypeInfo.Arrays.StatusCode,
+                "QualifiedName" => TypeInfo.Arrays.QualifiedName,
+                "LocalizedText" => TypeInfo.Arrays.LocalizedText,
+                "ExtensionObject" => TypeInfo.Arrays.ExtensionObject,
+                "Variant" => TypeInfo.Arrays.Variant,
+                "DataValue" => TypeInfo.Arrays.DataValue,
+                "DiagnosticInfo" => TypeInfo.Arrays.DiagnosticInfo,                
+                _ => throw new ServiceResultException(StatusCodes.BadDecodingError, $"Unsupported element type: {elementTypeName}")
+            };
+        }
+
         /// <summary>
         /// Read array items from current ListOf element
         /// </summary>

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

@@ -2175,11 +2175,9 @@ private void WriteMatrix(string fieldName, Matrix value)
 
                 if (value != null)
                 {
-                    m_writer.WriteStartElement("Elements", Namespaces.OpcUaXsd);
-                    WriteVariantContents(value.Elements, new TypeInfo(value.TypeInfo.BuiltInType, ValueRanks.OneDimension));
-                    m_writer.WriteEndElement();
-
                     WriteInt32Array("Dimensions", value.Dimensions);
+
+                    WriteArray("Elements", value.Elements, ValueRanks.OneDimension, value.TypeInfo.BuiltInType);
                 }
 
                 PopNamespace();

Tests/Opc.Ua.Core.Tests/Types/Encoders/XmlEncoderTests.cs

@@ -133,6 +133,49 @@ public void EncodeDecodeDouble(double binaryValue, string expectedXmlValue)
             else
                 Assert.AreEqual(actualBinaryValue, binaryValue);
         }
+
+        /// <summary>
+        /// Validate the encoding and decoding of the a variant that consists of a matrix.
+        /// </summary>
+        [Test]
+        public void EncodeDecodeVariantMatrix()
+        {
+            var value = new Matrix(
+                new int[] { 1, 2, 3, 4 },
+                BuiltInType.Int32,
+                new int[] { 2, 2 }
+            );
+            var variant = new Variant(value);
+
+            string expected = "<?xml version=\"1.0\" encoding=\"utf-16\"?>\r\n<uax:VariantTest xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns:uax=\"http://opcfoundation.org/UA/2008/02/Types.xsd\">\r\n  <uax:Test>\r\n    <uax:Value>\r\n      <uax:Matrix>\r\n        <uax:Dimensions>\r\n          <uax:Int32>2</uax:Int32>\r\n          <uax:Int32>2</uax:Int32>\r\n        </uax:Dimensions>\r\n        <uax:Elements>\r\n          <uax:Int32>1</uax:Int32>\r\n          <uax:Int32>2</uax:Int32>\r\n          <uax:Int32>3</uax:Int32>\r\n          <uax:Int32>4</uax:Int32>\r\n        </uax:Elements>\r\n      </uax:Matrix>\r\n    </uax:Value>\r\n  </uax:Test>\r\n</uax:VariantTest>";
+
+            // Encode
+            var context = new ServiceMessageContext();
+            string actualXmlValue;
+            using (IEncoder xmlEncoder = new XmlEncoder(new XmlQualifiedName("VariantTest", Namespaces.OpcUaXsd), null, context))
+            {
+                xmlEncoder.PushNamespace(Namespaces.OpcUaXsd);
+                xmlEncoder.WriteVariant("Test", variant);
+                xmlEncoder.PopNamespace();
+                actualXmlValue = xmlEncoder.CloseAndReturnText();
+            }
+
+            // Check encode result against expected XML value
+            Assert.AreEqual(expected.Replace("\r", "").Replace("\n", ""), actualXmlValue.Replace("\r", "").Replace("\n", ""));
+
+            // Decode
+            Variant actualVariant;
+            using (XmlReader reader = XmlReader.Create(new StringReader(actualXmlValue)))
+            {
+                using (IDecoder xmlDecoder = new XmlDecoder(null, reader, context))
+                {
+                    actualVariant = xmlDecoder.ReadVariant("Test");
+                }
+            }
+
+            // Check decode result against input value
+            Assert.AreEqual(actualVariant, variant);
+        }
         #endregion
     }
 }