EnumCraft.FeatureFlags 0.2.0-preview

EnumCraft.FeatureFlags

Strongly-typed, provider-based feature flags built on EnumCraft.Core.

Overview

EnumCraft.FeatureFlags provides a clean, extensible feature flag abstraction for .NET applications. Define your own strongly-typed flag catalog, plug in a data provider, and get type-safe flag resolution with per-tenant override support.

This package is part of the EnumCraft ecosystem:

Status

⚠️ This package is currently in preview. API surface is not yet stable and may change before v1.0.0.

Installation

dotnet add package EnumCraft.FeatureFlags
dotnet add package EnumCraft.FeatureFlags.Json

Requirements

• .NET Standard 2.0+ or .NET 8.0+
• EnumCraft.Core

Quick Start

1. Define your flag type

Each application defines its own concrete flag type. Each type has its own isolated provider, snapshot, and catalog.

using EnumCraft.FeatureFlags;

public sealed class AppFeatureFlag : FeatureFlag<AppFeatureFlag>
{
  public static readonly AppFeatureFlag DarkMode        = new(Guid.Parse("6255cf3c-2a18-4082-87f0-764bf76cc0f9"), "Dark Mode",        nameof(DarkMode),        isActiveDefault: false);
  public static readonly AppFeatureFlag NewDashboard    = new(Guid.Parse("c473d35a-c391-444b-86a7-4aac8319db4e"), "New Dashboard",    nameof(NewDashboard),    isActiveDefault: false);
  public static readonly AppFeatureFlag BetaReporting   = new(Guid.Parse("c74e06d8-1b6d-4614-8218-facb10da1ca6"), "Beta Reporting",   nameof(BetaReporting),   isActiveDefault: false);
  public static readonly AppFeatureFlag MaintenanceMode = new(Guid.Parse("aeba8047-b728-4e5b-8d66-f74f44a4bc76"), "Maintenance Mode", nameof(MaintenanceMode), isActiveDefault: false);

  private AppFeatureFlag(Guid id, string description, string code, bool isActiveDefault = false)
    : base(id, description, code, isActiveDefault) { }
}

2. Configure at startup

using EnumCraft.FeatureFlags.Json;

var options = new JsonFeatureFlagProviderOptions
{
  DirectoryPath = AppDomain.CurrentDomain.BaseDirectory,
  FileName      = "AppFeatureFlag.json"
};

var provider = new JsonFeatureFlagProvider(options);

if(!AppFeatureFlag.TryConfigure(provider, out var error))
{
  Console.WriteLine($"Failed to configure flags: {error}");
  return;
}

3. Use anywhere

// Global resolution
if(AppFeatureFlag.DarkMode.IsActive)
{
  // enabled globally
}

// Per-tenant resolution
if(AppFeatureFlag.DarkMode[tenantId])
{
  // enabled for this tenant
}

// Full resolution chain (for diagnostics)
var resolution = AppFeatureFlag.DarkMode.Resolve(tenantId);
foreach(var r in resolution)
{
  Console.WriteLine($"[{r.Priority}] {r.Source} → {r.Value}");
}

Resolution Order

For any flag lookup, the resolution priority is:

1. Tenant override — per-tenant value, if present in provider data
2. Global override — global value from provider data, if present
3. Constructor default — isActiveDefault parameter value

Implementing a Custom Provider

Implement IFeatureFlagProvider to load flag data from any source:

public class MyCustomProvider : IFeatureFlagProvider
{
  public event EventHandler? Changed;

  public bool Initialize(out string? error)
  {
    // load your data
    error = null;
    return true;
  }

  public FeatureFlagData GetSnapshot()
  {
    // return current data
  }

  public void Dispose() { }
}

License

MIT — see LICENSE for details.

Author

Randel Bjorkquist