Fix CallMethodResult.InputArgumentResults to comply with OPC UA Part 4 Section 5.12

[Copilot]

Proposed changes

Per OPC UA Part 4 Section 5.12, CallMethodResult.InputArgumentResults must be empty when StatusCode is Good. The array should only contain status codes when there are input argument errors.

Current behavior incorrectly populates InputArgumentResults with StatusCodes.Good for each valid argument:

// Before: Non-compliant behavior
if (argumentError != null) {
    result.InputArgumentResults.Add(argumentError.StatusCode);
} else {
    result.InputArgumentResults.Add(StatusCodes.Good);  // ❌ Violates spec
}

After fix:

// After: Spec-compliant behavior
if (argumentError != null) {
    result.InputArgumentResults.Add(argumentError.StatusCode);
}
// On success: clear the array
result.InputArgumentResults.Clear();  // ✅ Empty when StatusCode is Good

Changes:

• Removed population of StatusCodes.Good for valid arguments
• Clear InputArgumentResults when call succeeds (no argument errors)
• Updated in CustomNodeManager2 and SampleNodeManager

This ensures CTT compliance for method call status codes.

Related Issues

Related to compliance issue flagged for upcoming CTT release.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• Enhancement (non-breaking change which adds functionality)
• Test enhancement (non-breaking change to increase test coverage)
• Breaking change (fix or feature that would cause existing functionality to not work as expected, requires version increase of Nuget packages)
• Documentation Update (if none of the other choices apply)

Checklist

• I have read the CONTRIBUTING doc.
• I have signed the CLA.
• I ran tests locally with my changes, all passed.
• I fixed all failing tests in the CI pipelines.
• I fixed all introduced issues with CodeQL and LGTM.
• I have added tests that prove my fix is effective or that my feature works and increased code coverage.
• I have added necessary documentation (if appropriate).
• Any dependent changes have been merged and published in downstream modules.

Further comments

The fix is surgical: only removes non-compliant status code additions and ensures the array is cleared on success. All existing server tests pass without modification.

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Original prompt

---

This section details on the original issue you should resolve

<issue_title>Method calls shall return proper status codes</issue_title>
<issue_description>### Type of issue

• Bug
• Enhancement
• Compliance
• Question
• Help wanted

Current Behavior

The current behavior is unclear and needs investitagion if the spec is followed:

https://reference.opcfoundation.org/Core/Part4/v105/docs/5.12

The CTT will check this with the next release

Expected Behavior

No response

Steps To Reproduce

No response

Environment

- OS:
- Environment:
- Runtime:
- Nuget Version:
- Component:
- Server:
- Client:

Anything else?

No response</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Method calls shall return proper status codes #2356

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