[Server] Add support for SupportsFilteredRetain

[Archie-Miller]

Proposed changes

Add support for SupportsFilteredRetain - Issue 2142

This pull request introduces a new feature to support filtered retain conditions in the OPC UA server. The most important changes include adding a new method to determine if an event can be sent with filtered retain consideration, updating the MonitoredItem class to use this method, and adding a new property to the ConditionState class.

Enhancements to Event Filtering:

• Libraries/Opc.Ua.Server/Subscription/MonitoredItem.cs: Added the CanSendFilteredAlarm method to determine if an event can be sent with filtered retain consideration. This method checks if the event passes the filter and handles the condition ID for alarms with filtered retain.
• Libraries/Opc.Ua.Server/Subscription/MonitoredItem.cs: Updated the QueueEvent(IFilterTarget instance, bool bypassFilter) method to use the new CanSendFilteredAlarm method instead of directly evaluating the filter.
• Libraries/Opc.Ua.Server/Subscription/MonitoredItem.cs: Added a new private field m_filteredRetainConditionIds to store condition IDs for filtered retain.

Additions to ConditionState:

• Stack/Opc.Ua.Core/Stack/State/ConditionState.cs: Added a new public property SupportsFilteredRetain to the ConditionState class to indicate if the condition supports filtered retain.
• Stack/Opc.Ua.Core/Stack/State/ConditionState.cs: Added a new private field m_supportsFilteredRetain to store the value of the SupportsFilteredRetain property.

Types of changes

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• Bugfix (non-breaking change which fixes an issue)
• [ x ] 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

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your code.

• [ x ] I have read the CONTRIBUTING doc.
• [ x ] 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.
• [ x ] 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

One potential issue is that the ConditionState SupportsFilteredRetain property should be handled by the ObjectModeller. When this is implemented, this property and member variable will need to be removed.

[codecov]

Codecov Report

Attention: Patch coverage is 96.87500% with 1 line in your changes missing coverage. Please review.

Project coverage is 55.73%. Comparing base (23d167a) to head (2422c97).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...raries/Opc.Ua.Server/Subscription/MonitoredItem.cs	96.29%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2913      +/-   ##
==========================================
+ Coverage   55.41%   55.73%   +0.31%     
==========================================
  Files         352      352              
  Lines       67899    67930      +31     
  Branches    13931    13939       +8     
==========================================
+ Hits        37629    37861     +232     
+ Misses      26140    25917     -223     
- Partials     4130     4152      +22     

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[Copilot]

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

Comments suppressed due to low confidence (2)

Libraries/Opc.Ua.Server/Subscription/MonitoredItem.cs:1086

• [nitpick] The method name 'CanSendFilteredAlarm' is ambiguous. Consider renaming it to 'ShouldSendFilteredAlarm' to better reflect its purpose.

protected bool CanSendFilteredAlarm(FilterContext context, EventFilter filter, IFilterTarget instance)

Libraries/Opc.Ua.Server/Subscription/MonitoredItem.cs:1086

• The new behavior introduced by 'CanSendFilteredAlarm' should be covered by tests to ensure it works as expected.

protected bool CanSendFilteredAlarm(FilterContext context, EventFilter filter, IFilterTarget instance)

[Copilot]

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

Comments suppressed due to low confidence (3)

Libraries/Opc.Ua.Server/Subscription/MonitoredItem.cs:1045

• [nitpick] The method name 'CanSendFilteredAlarm' is ambiguous and does not clearly convey its purpose. Consider renaming it to 'ShouldSendFilteredAlarm' to better reflect its functionality.

if ( !CanSendFilteredAlarm( context, filter, instance ) )

Libraries/Opc.Ua.Server/Subscription/MonitoredItem.cs:1135

• The comment includes a date 'December 17 2024' which may be a typo or placeholder. Ensure the date is correct or remove it if unnecessary.

// Archie - December 17 2024

Libraries/Opc.Ua.Server/Subscription/MonitoredItem.cs:1144

• The variable 'saved' is used without being initialized in some cases. Ensure 'saved' is properly initialized before use to avoid potential null reference errors.

if ( saved )

[mrsuciu]

Why is the ConditionId only valid if FilteredRetain is set ?

[Archie-Miller]

The logic is specifically for SupportsFilterRetain, so if it is not set, the remainder of the function is not required, only the filter check at the top of the function.

This is still a work in progress, I'm going to move it to draft for now.

[romanett]

@Archie-Miller can you describe, what is still missing for this PR to be ready to merge

[Archie-Miller]

Hello Roman, I'm pretty happy with this, I have an outstanding email with Paul on this, but I think it's fine to put in the customer's hand to work with. Have a good day, Archie

…

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