How to Implement Hierarchical Feature Dependencies Without Circular DI?

[ShayMusachanov-dev]

Context

I'm implementing hierarchical feature dependencies where one feature can depend on other features being enabled. I'm using a database-backed provider (similar to PR #389) with AddScopedFeatureManagement().

The Scenario

I want to implement a FeatureDependency filter that allows one feature to depend on others:

{
  "id": "Dashboard",
  "enabled": true,
  "conditions": {
    "requirement_type": "Any",
    "client_filters": [
      {
        "name": "FeatureDependency",
        "parameters": { "FeatureName": "BasicReporting" }
      },
      {
        "name": "FeatureDependency",
        "parameters": { "FeatureName": "AdvancedReporting" }
      }
    ]
  }
}

The Dashboard feature should be enabled if either BasicReporting OR AdvancedReporting is enabled.

These dependent features themselves have their own conditions:

{
  "id": "BasicReporting",
  "enabled": true,
  "conditions": {
    "client_filters": [
      {
        "name": "TimeWindow",
        "parameters": { "Start": "...", "End": "..." }
      }
    ]
  }
}

{
  "id": "AdvancedReporting",
  "enabled": true,
  "conditions": {
    "requirement_type": "All",
    "client_filters": [
      {
        "name": "Percentage",
        "parameters": { "Value": 50 }
      },
      {
        "name": "FeatureDependency",
        "parameters": { "FeatureName": "PremiumSubscription" }
      }
    ]
  }
}

To properly evaluate Dashboard, the FeatureDependency filter needs to evaluate BasicReporting and AdvancedReporting through their complete filter pipeline (TimeWindow, Percentage, nested dependencies, etc.). This requires calling IFeatureManager.IsEnabledAsync().

What I Tried

I implemented the filter like this:

[FilterAlias("FeatureDependency")]
public class FeatureDependencyFilter : IFeatureFilter
{
    private readonly IFeatureManager _featureManager;

    public FeatureDependencyFilter(IFeatureManager featureManager)
    {
        _featureManager = featureManager;
    }

    public async Task<bool> EvaluateAsync(FeatureFilterEvaluationContext context)
    {
        string? featureName = context.Parameters.GetValue<string>("FeatureName");
        
        if (string.IsNullOrEmpty(featureName))
        {
            return false;
        }

        return await _featureManager.IsEnabledAsync(featureName);
    }
}

Registered with:

services.AddScopedFeatureManagement()
        .AddFeatureFilter<FeatureDependencyFilter>();

The Problem

This creates a circular dependency during DI container construction:

IFeatureManager (being created)
  → needs IFeatureFilterMetadata[] (including FeatureDependencyFilter)
    → FeatureDependencyFilter constructor needs IFeatureManager
      → Circular dependency!

Result: The application hangs indefinitely when trying to resolve IFeatureManager:

using (IServiceScope scope = serviceProvider.CreateScope())
{
    IFeatureManager featureManager = scope.ServiceProvider.GetRequiredService<IFeatureManager>();
}

The Solution I Arrived At

Breaking the circular dependency by resolving IFeatureManager at evaluation time instead of in the constructor:

[FilterAlias("FeatureDependency")]
public class FeatureDependencyFilter : IFeatureFilter
{
    private readonly IServiceProvider _serviceProvider;

    public FeatureDependencyFilter(IServiceProvider serviceProvider)
    {
        _serviceProvider = serviceProvider;
    }

    public async Task<bool> EvaluateAsync(FeatureFilterEvaluationContext context)
    {
        string? featureName = context.Parameters.GetValue<string>("FeatureName");
        
        if (string.IsNullOrEmpty(featureName))
        {
            return false;
        }

        IFeatureManager featureManager = _serviceProvider.GetRequiredService<IFeatureManager>();
        return await featureManager.IsEnabledAsync(featureName);
    }
}

Questions

1. Is this the recommended pattern for implementing hierarchical feature dependencies?
2. Is there a built-in way to express feature dependencies without creating a custom filter?
3. Is using IServiceProvider directly the correct approach to break the circular dependency, or is there a better pattern?
4. Does the default configuration-based provider handle cycle detection? If feature dependencies form a cycle (e.g., FeatureA → FeatureB → FeatureA), does the library have built-in safeguards, or should I implement my own cycle detection?

---

Any guidance on the proper pattern for hierarchical feature dependencies would be greatly appreciated!

[zhiyuanliang-ms]

Hey, @ShayMusachanov-dev Could you try the solution I proposed in issue #568.

I used Lazy<IFeatureManager> instead of passing the whole service provider to the filter.

[jimmyca15]

Hello @ShayMusachanov-dev

We are looking for some input as we consider adding this functionality built-in to the library. Is it enough to say that the desire here is to be able to turn off a group of features at once? If so we, we may consider to introduce the capability to group features rather than introduce dependency chains.