Mastering Feature Flags with Laravel Pennant

Laravel Pennant is a powerful and lightweight feature flag package introduced in Laravel 10. It allows developers to easily implement feature toggles, enabling incremental rollouts, A/B testing, and more flexible development strategies. In this post, we'll explore how to use Pennant and showcase some practical examples.

Getting Started with Laravel Pennant

First, let's install Pennant:

composer require laravel/pennant
php artisan vendor:publish --provider="Laravel\Pennant\PennantServiceProvider"
php artisan migrate

Defining Features

There are two main ways to define features in Pennant:

Using the Feature Facade

In your AppServiceProvider:

use Laravel\Pennant\Feature;
use App\Models\User;

public function boot()
{
    Feature::define('new-dashboard', function (User $user) {
        return $user->isAdmin() || $user->created_at->isAfter(now()->subDays(30));
    });
}

Using Class-Based Features

Create a new feature class:

php artisan pennant:feature NewDashboard

Then define the logic in the class:

namespace App\Features;

use App\Models\User;

class NewDashboard
{
    public function resolve(User $user): bool
    {
        return $user->isAdmin() || $user->created_at->isAfter(now()->subDays(30));
    }
}

Checking Features

You can check if a feature is active in several ways:

// In controllers or other parts of your application
if (Feature::active('new-dashboard')) {
    // Show new dashboard
}

// For class-based features
if (Feature::active(NewDashboard::class)) {
    // Show new dashboard
}

// In Blade templates
@feature('new-dashboard')
    <x-new-dashboard />
@else
    <x-old-dashboard />
@endfeature

Suggested Usages

• Gradual Feature Rollout

  Roll out a new feature to a percentage of users:

  Feature::define('new-chat', function (User $user) {
      return $user->id % 100 < 25; // 25% of users
  });

• A/B Testing

  Implement A/B testing for a new UI design:

  Feature::define('new-ui', function (User $user) {
      return $user->id % 2 === 0; // 50% of users see new UI
  });

• Beta Testing Program

  Allow certain users to access beta features:

  Feature::define('beta-feature', function (User $user) {
      return $user->isBetaTester();
  });

• Geographic Feature Availability

  Enable features based on user location:

  Feature::define('eu-compliance', function (User $user) {
      return $user->country->isInEU();
  });

• Feature Toggles in API

  Use feature flags to version your API:

  Route::middleware('auth:api')->group(function () {
      Route::get('/data', function (Request $request) {
          if (Feature::active('new-api-version')) {
              return $this->newApiResponse();
          }
  
          return $this->legacyApiResponse();
      });
  });

Best Practices

• Use Descriptive Names: Choose clear, descriptive names for your features to make them easily understandable.

• Keep Logic Simple: Try to keep the feature resolution logic simple and focused.

• Leverage Scopes: Use Pennant's scoping capabilities to check features for specific models or entities.

• Clean Up Unused Flags: Regularly review and remove feature flags that are no longer needed.

• Test Both States: Always test your application with the feature both active and inactive.

Laravel Pennant provides a clean and efficient way to implement feature flags in your Laravel applications. By leveraging its capabilities, you can achieve more flexible, controlled, and testable feature releases. Whether you're implementing gradual rollouts, conducting A/B tests, or managing complex feature sets, Pennant offers the tools to make your development process smoother and more robust.

Remember, feature flags are powerful tools, but they should be used judiciously. Over-reliance on feature flags can lead to complex codebases, so always consider the long-term implications of each flag you introduce.