Allow minimal Rails installs that don't include all dependencies

.github/workflows/ci.yml

@@ -28,6 +28,22 @@ jobs:
           - ruby: '2.7'
             rails: '6.1'
             bundler: 'default'
+          - ruby: '3.0'
+            rails: '6.1'
+            bundler: 'default'
+          - ruby: '3.1'
+            rails: '6.1'
+            bundler: 'default'
+          - ruby: '3.2'
+            rails: '7'
+            bundler: 'default'
+          - ruby: '3.3'
+            rails: '7'
+            bundler: 'default'
+          - ruby: '3.4'
+            rails: '8'
+            bundler: 'default'
+
     env:
       RAILS_VERSION: ${{ matrix.rails }}
 
@@ -39,14 +55,14 @@ jobs:
           bundler: ${{ matrix.bundler }}
           bundler-cache: true
       - run: bundle exec rubocop
-        if: matrix.ruby == '2.7'
+        if: matrix.ruby == '3.4'
       - run: bundle exec rspec --format doc
       - uses: codecov/codecov-action@v3
-        if: matrix.ruby == '2.7'
+        if: matrix.ruby == '3.4'
         with:
           files: coverage/coverage.xml
       - run: bin/yardoc --fail-on-warning
-        if: matrix.ruby == '2.7'
+        if: matrix.ruby == '3.4'
       - run: bin/check-version
 
   release:

lib/epilog/rails.rb

@@ -1,23 +1,23 @@
 # frozen_string_literal: true
 
-require 'action_controller/log_subscriber'
-require 'action_dispatch/middleware/debug_exceptions'
-require 'action_mailer/log_subscriber'
-require 'action_view/log_subscriber'
-require 'active_record/log_subscriber'
-require 'active_job/logging'
+require 'action_controller/log_subscriber' if Gem.loaded_specs.key?('action_controller')
+require 'action_dispatch/middleware/debug_exceptions' if Gem.loaded_specs.key?('action_dispatch')
+require 'action_mailer/log_subscriber' if Gem.loaded_specs.key?('action_mailer')
+require 'action_view/log_subscriber' if Gem.loaded_specs.key?('action_view')
+require 'active_record/log_subscriber' if Gem.loaded_specs.key?('active_record')
+require 'active_job/logging' if Gem.loaded_specs.key?('active_job')
 
 require 'epilog/rails/ext/event_delegate'
 require 'epilog/rails/ext/active_support_logger'
 require 'epilog/rails/ext/rack_logger'
-require 'epilog/rails/ext/action_controller'
+require 'epilog/rails/ext/action_controller' if Gem.loaded_specs.key?('action_controller')
 require 'epilog/rails/ext/debug_exceptions'
 
 require 'epilog/rails/epilog_ext'
 require 'epilog/rails/log_subscriber'
-require 'epilog/rails/action_controller_subscriber'
-require 'epilog/rails/action_mailer_subscriber'
-require 'epilog/rails/action_view_subscriber'
-require 'epilog/rails/active_record_subscriber'
-require 'epilog/rails/active_job_subscriber'
+require 'epilog/rails/action_controller_subscriber' if Gem.loaded_specs.key?('action_controller')
+require 'epilog/rails/action_mailer_subscriber' if Gem.loaded_specs.key?('action_mailer')
+require 'epilog/rails/action_view_subscriber' if Gem.loaded_specs.key?('action_view')
+require 'epilog/rails/active_record_subscriber' if Gem.loaded_specs.key?('active_record')
+require 'epilog/rails/active_job_subscriber' if Gem.loaded_specs.key?('active_job')
 require 'epilog/rails/railtie'

lib/epilog/rails/railtie.rb

@@ -10,25 +10,25 @@ def self.rails_6_1_higher?
       # We need this in Rails 6.
       # Without this line `ActiveJob::LogSubscriber` fails
       # with unknown contant error
-      ActiveSupport.run_load_hooks(:active_job, ActiveJob::Base)
+      ActiveSupport.run_load_hooks(:active_job, ActiveJob::Base) if defined?(ActiveJob::Base)
 
       SUBSCRIBERS = {
-        action_controller: ActionControllerSubscriber,
-        action_mailer: ActionMailerSubscriber,
-        action_view: ActionViewSubscriber,
-        active_record: ActiveRecordSubscriber,
-        active_job: ActiveJobSubscriber
+        action_controller: 'ActionControllerSubscriber',
+        action_mailer: 'ActionMailerSubscriber',
+        action_view: 'ActionViewSubscriber',
+        active_record: 'ActiveRecordSubscriber',
+        active_job: 'ActiveJobSubscriber'
       }.freeze
 
       SUBSCRIBER_BLACKLIST = [
-        ActionController::LogSubscriber,
-        ActionMailer::LogSubscriber,
-        ActionView::LogSubscriber,
-        ActiveRecord::LogSubscriber,
+        'ActionController::LogSubscriber',
+        'ActionMailer::LogSubscriber',
+        'ActionView::LogSubscriber',
+        'ActiveRecord::LogSubscriber',
         if rails_6_1_higher?
-          ActiveJob::LogSubscriber
+          'ActiveJob::LogSubscriber'
         else
-          ActiveJob::Logging::LogSubscriber
+          'ActiveJob::Logging::LogSubscriber'
         end
       ].freeze
 
@@ -49,7 +49,9 @@ def self.rails_6_1_higher?
         ::Rails.logger ||= Logger.new($stdout)
 
         app.config.epilog.subscriptions.each do |namespace|
-          subscriber_class = SUBSCRIBERS[namespace]
+          subscriber_class = SUBSCRIBERS[namespace].safe_constantize
+          next unless subscriber_class
+
           subscriber_class.attach_to(
             namespace,
             subscriber_class.new(::Rails.logger)
@@ -78,7 +80,7 @@ def unsubscribe_listeners(subscriber, pattern)
 
       def blacklisted_subscribers
         ActiveSupport::LogSubscriber.log_subscribers.select do |subscriber|
-          SUBSCRIBER_BLACKLIST.include?(subscriber.class)
+          SUBSCRIBER_BLACKLIST.include?(subscriber.class.name)
         end
       end
     end