FeatureGuard

FeatureGuard protects Rails controller actions with feature flags stored on an account's settings record. It also exposes the same checks to views.

Installation

Add the gem to the Rails application's Gemfile:

gem "rails_feature_guard"

Then install dependencies:

bundle install

Configuration

Create config/initializers/feature_guard.rb:

FeatureGuard.configure do |config|
  config.redirect_method = :dashboards_path
end

The default values are:

redirect_method: :root_path

redirect_method is combined with the controller's first namespace. For example, :dashboards_path in a Partner controller becomes partner_dashboards_path.

Settings record

The account's settings record must have a boolean attribute for each feature:

# current_account.feature_setting
inventory_enabled # true or false
reports_enabled   # true or false

For example, an account can expose its settings record like this:

class Account < ApplicationRecord
  has_one :feature_setting
end

Protect a controller action

Declare a feature in a controller:

class InventoryController < ApplicationController
  feature :inventory_enabled

  def index
  end
end

The feature name must exactly match a boolean column on current_account.feature_setting. feature :inventory_enabled calls inventory_enabled? on the feature policy. When that method is not defined, the policy reads inventory_enabled? from the settings record. If that column is missing, FeatureGuard raises FeatureGuard::MissingFeatureColumnError. FeatureGuard adds a before_action:

inventory_enabled is true  -> the action runs
inventory_enabled is false -> the request redirects

Limit a feature check to specific actions with normal before_action options:

class InventoryController < ApplicationController
  feature :inventory_enabled, only: :index
end

For example, feature :inventory_access_enabled requires an inventory_access_enabled settings column and uses inventory_access_enabled? on both the policy and settings record.

Feature policy

Create a policy in the Rails application and have the host controller provide one instance per request. Include FeatureGuard::Policy; the module provides the common feature-resolution behavior.

# app/policies/feature_policy.rb
class FeaturePolicy
  include FeatureGuard::Policy

  def inventory_enabled?
    current_user.admin?
  end
end

# app/controllers/application_controller.rb
class ApplicationController < ActionController::Base
  private

  def feature_guard_policy
    @feature_guard_policy ||= FeaturePolicy.new(
      current_user: current_user,
      feature_setting: current_account&.feature_setting
    )
  end
end

The policy receives the account's feature_setting and current_user. A defined policy method fully controls its declared feature. When it is absent, FeatureGuard::Policy#method_missing reads the identically named setting predicate. Policy and settings names must match exactly.

Define the private #feature_guard_policy instance method on the base controller so all controllers can build a request policy. For namespaced controllers, define it on that namespace's base controller. If it is missing, the gem raises FeatureGuard::MissingPolicyError.

To use a differently named factory method, select it with the class-level feature_guard_policy_method declaration:

feature_guard_policy_method :my_custom_feature_policy

Use a feature in a view

module_enabled? is available in controller actions and views:

<% if module_enabled?(:inventory_enabled) %>
  <%= link_to "Inventory", inventory_path %>
<% end %>

You may use module_enabled? without declaring feature :inventory_enabled in the controller. Declaring feature is only required when you want FeatureGuard to add the automatic redirect callback.

Errors and missing settings

• If the account has no settings record, module_enabled? returns false.
• If the settings record lacks the expected feature column, FeatureGuard raises FeatureGuard::MissingFeatureColumnError.
• If the base controller does not implement feature_guard_policy, FeatureGuard raises FeatureGuard::MissingPolicyError.
• If the namespaced dashboard route does not exist, FeatureGuard raises FeatureGuard::MissingRouteError.