CPS - How To Conditionally show a property on a ProjectReference browse object based on the *referenced* project's properties?

[ArZei]

This is a copy of my report on developer community: https://developercommunity.visualstudio.com/t/CPSExtensibility---How-To-Conditionally/11124279

Greetings,

We are a third-party language extender in Visual Studio. We have a custom CPS-based project system (a .synproj project type) and we are trying to find out how to conditionally show a property/metadata under a project reference's properties window, as such:

We would like to filter the visibility of this metadata so it shows only when the referenced project has a specific characteristic (in my case OutputType=RPS, but flexible and can be Capability based, etc.)

This is largely driven by the XAML rule below:

<?xml version="1.0" encoding="utf-8"?>
<!--Copyright, Microsoft Corporation, All rights reserved.-->
<Rule
    Name="ProjectReference"
    DisplayName="Project Reference"
    PageTemplate="custom"
    Description="Project Reference Properties"
    OverrideMode="Extend"
    xmlns="http://schemas.microsoft.com/build/2009/properties">

  <Rule.DataSource>
    <DataSource HasConfigurationCondition ="False" Persistence="ProjectFile" ItemType="ProjectReference" />
  </Rule.DataSource>

  <BoolProperty
      Name="Default"
      Visible="True"
      DisplayName="Default Repository"
      Description="Default Repository" />
</Rule>

Approaches tried and results:

1. XAML rule using AppliesTo or VisibilityCondition
   Doesn't work because this filters based on the referencing project, not the referenced project, and the rule is loaded up-front before any kind of logic we can run on the project references.

2. Property page factory via IPropertyPageUIFactoryProvider
   Implemented a property page factory, MEF imported and ProjectCapability controlled. Tried to provide our own custom property view. Doesn't seem to hit the property windows under CPS.

3. Design-time item reclassification of ProjectReference into a custom type (ex. RepositoryReference)
   Created a target (gated on DesignTimeBuild/BuildingInsideVisualStudio, BeforeTargets="ResolveProjectReferences") reclassifies qualifying ProjectReference items to a custom RepositoryReference item type, with a matching BrowseObject-context XAML rule carrying the property. Verified via design-time build log that the reclassification runs and produces the correct item. The property still does not appear, and the reference node's browse object remains bound to the built-in ProjectReference type

4. Automation extender via IExtenderCATIDProvider
   Implemented and exported the provider; it returns a CATID for ExtenderCATIDType.ReferenceBrowseObject. Registered an IExtenderProvider under that CATID. CanExtend is called and returns the correct per-reference boolean for filtering. However GetExtender is never called so our custom property show and getter/setter never gets hit.

Questions:

1. Is there a supported way to conditionally show a property on a project reference browse object based on the referenced project's properties/capabilities?

2. The IExtenderCATIDProvider approach in particular was very promising until we encountered the blocker. Is GetExtender not being called after a successful CanExtend on these project reference nodes expected behavior?

If there is a supported way to achieve conditional per-reference property visibility in the Properties window for a CPS project system, I'd appreciate guidance. If not, please treat this as a feature request for that capability and separately, the CanExtend/GetExtender discrepancy above appears to be a bug.

Thank you and please let me know if any clarification is needed.
Arief Zein