DataItemType and its sub types have incorrect ValueRank

[saurla]

Type of issue

• Bug
• Enhancement
• Compliance
• Question
• Help wanted

Current Behavior

DataItemType has ValueRank 0 = OneOreMoreDimensions. Also all sub types of DataItemType have ValueRank 0. See attached image illustrating the problem .

Expected Behavior

Based on the specification (https://reference.opcfoundation.org/Core/Part8/v105/docs/5.3.1), DataItemType should have ValueRank -2 = Any.

Steps To Reproduce

1. Compile ConsoleReferenceServer
2. Start ConsoleReferenceServer
3. Connect to ConsoleReferenceServer
4. Read ValueRank Attribute of the DataItemType node (i=2365)
5. Observe invalid ValueRank 0

Environment

- OS: Windows 11
- Environment: Visual Studio 2022
- Runtime: .NET
- Nuget Version: .NET 9.0
- Component: Not sure where the problem is, might be Opc.Ua.Core or UA-ModelCompiler
- Server: ConsoleReferenceServer
- Client: Ua Expert

Anything else?

No response

[saurla]

Based on quick investigation I think it's the same problem that was already once fixed: #750.

In the UA-ModelCompiler there was a fix in this commit OPCFoundation/UA-ModelCompiler@5f2afa3#diff-8895de6ce47cd3e1f1cfbb067696a6e97e5fda1ec30accf02f5228defe66a230R1062 which fixed GetAttributesToSave methods in BaseVariableState and BaseVariableTypeState to persist ValueRank correctly to initialization string. At that point UA-ModelCompiler used its own copy of the Opc.Ua.Core. Now it seems to be linked to this repository as sub-module and the fix most likely was never done to this repo.

So most likely to fix this following is needed:

• Make the same fix to this repository
• Update UA-ModelCompiler to use the version of this repository where fix is done
• Generate node sets
• Take node sets in to use in Opc.Ua.Core

[saurla]

More investigation shows that ValueRank is not written to InitializationString if its value is Any. This is in a way fine since it also won't be read from the InitializationString and instead value returned by the GetDefaultValueRank() of the type is used. So instantiating DataItemState in code works fine.

Problem is with the UA-ModelCompiler when it compiles the nodeset file Opc.Ua.PredefinedNodes.uanodes. The ValueRank there is left to default int value 0 because GetAttributesToSave() does not return ValueRank attribute when ValueRank is -2.

I tested the solution I suggested in previous comment and was able to generate Opc.Ua.PredefinedNodes.uanodes when the ValueRank was correctly -2.

[saurla]

I have written a test case to reproduce the issue:

using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Iced.Intel;
using NUnit.Framework;
using static Opc.Ua.NodeState;
using Assert = NUnit.Framework.Legacy.ClassicAssert;

namespace Opc.Ua.Core.Tests.Stack.State
{
    /// <summary>
    /// Tests serialization and deserialization of BaseDataVariableTypeState
    /// </summary>
    [TestFixture]
    [SetCulture("en-us"), SetUICulture("en-us")]
    public class BaseDataVariableTypeStateSerializationTest
    {
        [Test]
        public void ValueRankPersistingTest(
            [Values(ValueRanks.ScalarOrOneDimension, ValueRanks.Any, ValueRanks.Scalar,
            ValueRanks.OneOrMoreDimensions, ValueRanks.OneDimension, ValueRanks.TwoDimensions)] int valueRank)
        {
            var variable = new BaseDataVariableTypeState();
            var serviceMessageContext = new ServiceMessageContext();

            var systemContext = new SystemContext() { NamespaceUris = serviceMessageContext.NamespaceUris };

            variable.Create(
                    new SystemContext() { NamespaceUris = serviceMessageContext.NamespaceUris },
                    VariableTypeIds.DataItemType,
                    BrowseNames.DataItemType,
                    new LocalizedText("DataItemType"),
                    true);

            variable.ValueRank = valueRank;

            var loadedVariable = new BaseDataVariableTypeState();

            using (MemoryStream stream = new MemoryStream())
            {
                variable.SaveAsBinary(systemContext, stream);
                
                stream.Position = 0;
                loadedVariable.LoadAsBinary(systemContext, stream);
            }

            Assert.AreEqual(valueRank, loadedVariable.ValueRank);
        }
    }
}

[saurla]

I also found out another potential way to fix this which does not require regeneration of nodeset files. It could be possible to add Initialize(context) call before this line

UA-.NETStandard/Stack/Opc.Ua.Core/Stack/State/NodeState.cs

Line 681 in 2f0770c

Update(context, decoder, attributesToLoad);

, which would make sure all values are set to default values read from the InitializationString before reading values from the BinaryDecoder. However, I'm not sure if there would be any unwanted side effects from the Initialize call.

[saurla]

If needed I'm ready to work on this issue and submit a PR when there is a decision how to fix the issue.

[saurla]

The Initialize(context) call inside LoadAsBinary was not good idea after all since Initialize of generated classes will also call LoadAsBinary causing an infinite recursion.

[mrsuciu]

@saurla Thank you for raising the issue and for the investigation. Stay tuned until a decision on which the best approach is decided.