Arbeidstilsynet.Common.FeatureFlags 1.1.2

Introduction

A feature flag library for .NET applications using Unleash as the backing service. This package provides a simple interface for checking feature flags with support for context-based evaluation.

📖 Installation

To install the FeatureFlags package, you can use the following command in your terminal:

dotnet add package Arbeidstilsynet.Common.FeatureFlags

🧑‍💻 Usage

Configuration

Add feature flag settings to your appsettings.json:

{
  "FeatureFlags": {
    "Url": "https://unleash.example.com/api",
    "ApiKey": "your-api-key-here",
    "AppName": "my-application"
  }
}

Service Registration

Add to your service collection in Program.cs or Startup.cs:

using Arbeidstilsynet.Common.FeatureFlags.DependencyInjection;
using Arbeidstilsynet.Common.FeatureFlags.Model;

var builder = WebApplication.CreateBuilder(args);

// Bind configuration
var featureFlagSettings = builder.Configuration
    .GetSection("FeatureFlags")
    .Get<FeatureFlagSettings>();

// Register feature flags service
builder.Services.AddFeatureFlags(
    builder.Environment,
    featureFlagSettings
);

var app = builder.Build();

Note: If featureFlagSettings is null or has missing configuration, the service will automatically use FakeUnleash for testing purposes.

Using Feature Flags in Your Code

Inject IFeatureFlags into your services or controllers:

using Arbeidstilsynet.Common.FeatureFlags.Model;
using Arbeidstilsynet.Common.FeatureFlags.Ports;

public class MyService
{
    private readonly IFeatureFlags _featureFlags;

    public MyService(IFeatureFlags featureFlags)
    {
        _featureFlags = featureFlags;
    }

    public void DoSomething()
    {
        // Simple feature check
        if (_featureFlags.IsEnabled("my-new-feature"))
        {
            // New feature logic
        }
        else
        {
            // Old logic
        }
    }

    public void DoSomethingWithContext(string userId)
    {
        // Feature check with context
        var context = new FeatureFlagContext
        {
            UserId = userId,
        };

        if (_featureFlags.IsEnabled("user-specific-feature", context))
        {
            // Context-aware feature logic
        }
    }
}

Mapping the Feature Flag Endpoint

You can expose an HTTP endpoint to check feature flags remotely:

using Arbeidstilsynet.Common.FeatureFlags.DependencyInjection;

var app = builder.Build();

app.UseRouting();

// Map with default route: POST /feature-flags
app.MapFeatureFlagEndpoint();

// Or with a custom route:
app.MapFeatureFlagEndpoint("/api/features");

app.Run();

Example request:

POST /feature-flags
Content-Type: application/json

{
  "featureName": "my-new-feature",
  "context": {
    "userId": "user123"
  }
}

Example response:

{
  "featureName": "my-new-feature",
  "isEnabled": true
}

🧪 Testing

For testing purposes, when no configuration is provided, the service automatically uses FakeUnleash:

// In your test setup
services.AddFeatureFlags(webHostEnvironment, null);

You can also configure specific features to be enabled in tests:

var fakeUnleash = new FakeUnleash();
fakeUnleash.Enable("test-feature");
services.AddSingleton<IUnleash>(fakeUnleash);
services.AddFeatureFlags(webHostEnvironment, null);