Installed FlipFlop gem

We are installing the FlipFlop gem to enable us to use feature flags with a lower barrier to entry that the current process of using user permissions. The FlipFlop gem can store feature flag information inside the Whitehall database, meaning that we no longer have to create permissions inside of signon to deploy code without releasing it to users.

We have disabled the cookie strategy because our main use case at the moment is toggling features on and off in different environments, but we may consider using it in future if our needs change.

We have also only enabled the Flipflop user interface in local development environments. Developers will use the rake task provided by the library to toggle features in cloud environments.

This commit also switches the FlipFlop strategy to use an in-memory store for feature flags and makes the flag data available to test cases.

Gemfile

@@ -12,6 +12,7 @@ gem "carrierwave-i18n"
 gem "chronic"
 gem "dalli"
 gem "diffy"
+gem "flipflop"
 gem "fog-aws"
 gem "friendly_id"
 gem "fuzzy_match"

Gemfile.lock

@@ -200,6 +200,9 @@ GEM
     ffi (1.15.5)
     filelock (1.1.1)
     find_a_port (1.0.1)
+    flipflop (2.7.1)
+      activesupport (>= 4.0)
+      terminal-table (>= 1.8)
     fog-aws (3.21.0)
       fog-core (~> 2.1)
       fog-json (~> 1.1)
@@ -967,6 +970,7 @@ DEPENDENCIES
   equivalent-xml
   erb_lint
   factory_bot
+  flipflop
   fog-aws
   friendly_id
   fuzzy_match

config/application.rb

@@ -91,5 +91,13 @@ class Application < Rails::Application
     unless Rails.application.secrets.jwt_auth_secret
       raise "JWT auth secret is not configured. See config/secrets.yml"
     end
+
+    # Before filter for Flipflop dashboard. Replace with a lambda or method name
+    # defined in ApplicationController to implement access control.
+    config.flipflop.dashboard_access_filter = -> { head :forbidden unless ENV["RAILS_ENV"] == "development" }
+
+    # By default, when set to `nil`, strategy loading errors are suppressed in test
+    # mode. Set to `true` to always raise errors, or `false` to always warn.
+    config.flipflop.raise_strategy_errors = nil
   end
 end

config/features.rb

@@ -0,0 +1,23 @@
+Flipflop.configure do
+  # Strategies will be used in the order listed here.
+  strategy :active_record
+  strategy :default
+
+  # Other strategies:
+  #
+  # strategy :sequel
+  # strategy :redis
+  #
+  # strategy :query_string
+  # strategy :session
+  #
+  # strategy :my_strategy do |feature|
+  #   # ... your custom code here; return true/false/nil.
+  # end
+
+  # Declare your features, e.g:
+  #
+  # feature :world_domination,
+  #   default: true,
+  #   description: "Take over the world."
+end

config/routes.rb

@@ -397,5 +397,7 @@ def redirect(path, options = { prefix: Whitehall.router_prefix })
 
   mount SidekiqGdsSsoMiddleware, at: "/sidekiq"
 
+  mount Flipflop::Engine => "/flipflop"
+
   mount GovukPublishingComponents::Engine, at: "/component-guide" unless Rails.env.production?
 end

db/migrate/20231102101641_create_features.rb

@@ -0,0 +1,10 @@
+class CreateFeatures < ActiveRecord::Migration[7.0]
+  def change
+    create_table :flipflop_features do |t|
+      t.string :key, null: false
+      t.boolean :enabled, null: false, default: false
+
+      t.timestamps null: false
+    end
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.0].define(version: 2023_10_31_222012) do
+ActiveRecord::Schema[7.0].define(version: 2023_11_02_101641) do
   create_table "assets", charset: "utf8mb3", force: :cascade do |t|
     t.string "asset_manager_id", null: false
     t.string "variant", null: false
@@ -501,6 +501,13 @@
     t.index ["year"], name: "index_financial_reports_on_year"
   end
 
+  create_table "flipflop_features", charset: "utf8mb3", force: :cascade do |t|
+    t.string "key", null: false
+    t.boolean "enabled", default: false, null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+  end
+
   create_table "force_publication_attempts", id: :integer, charset: "utf8mb3", force: :cascade do |t|
     t.integer "import_id"
     t.integer "total_documents"

docs/feature_flags.md

@@ -0,0 +1,25 @@
+# Feature Flags
+
+Feature flags in Whitehall are managed using the [FlipFlop gem](https://github.com/voormedia/flipflop). The gem is currently
+configured so that only the ActiveRecord and default strategies are active.
+
+## Toggling Feature Flags
+
+In local development environments, a UI is available to make it easy to toggle feature flags on and off during development.
+The UI can be accessed at http://whitehall-admin.dev.gov.uk/flipflop. To toggle feature flags in non-local environments, the
+rake task provided by FlipFlop can be used, e.g.
+
+```bash
+bundle exec rake flipflop:turn_on[new_feature,active_record]   # Enables the new feature with the Active Record strategy
+bundle exec rake flipflop:turn_off[new_feature,active_record]  # Disables the new feature with the Active Record strategy
+```
+
+## Testing with Feature Flags
+
+Feature flags are made accessible via the [`feature_flags`] helper on `ActionController::TestCase`.
+
+To toggle a feature flag in your controller test:
+
+```ruby
+feature_flags.switch! :your_feature, true
+```

test/test_helper.rb

@@ -209,10 +209,13 @@ class ActionController::TestCase
   include Admin::EditionRoutesHelper
 
   attr_reader :current_user
+  attr_reader :feature_flags
 
   setup do
     request.env["warden"] = stub(authenticate!: false, authenticated?: false, user: nil)
 
+    @feature_flags = Flipflop::FeatureSet.current.test!
+
     # In controller tests, stub out all calls to the content store. This
     # implies that by default we don't care about responses from this endpoint,
     # which is currently only used to render specialist sector links in the