railties/active_record: read 'adapter' without requiring a DB conn

Fixes #1222
(Airbrake Gem Attempts to Connect to Database in Databaseless App in Rails 6)

Good article:
https://www.bigbinary.com/blog/rails-6-changed-activerecord-base-configurations-result-to-an-object

We also add a guard that makes sure there's an ActiveRecord configuration
present (it can be that ActiveRecord is required but not configured; why? I have
no idea but it did happen to our customer and he's got no clue either).

CHANGELOG.md

@@ -6,6 +6,9 @@ Airbrake Changelog
 * Fixed support of APM on Rails 7+, where the reported time of a route was
  malformed, resulting in the complete rejection of the route stats by the
  backend ([#1223](https://github.com/airbrake/airbrake/issues/1223))
+* Fixed bug where Rails 6+ apps that don't require ActiveRecord crash when
+ Airbrake is installed
+ ([#1224](https://github.com/airbrake/airbrake/pull/1224))
 
 ### [v13.0.0][v13.0.0] (January 18, 2022)
 

lib/airbrake/rails/railties/active_record_tie.rb

@@ -34,7 +34,15 @@ def tie_activerecord_callback_fix
  end
 
  def tie_activerecord_apm
- return unless defined?(ActiveRecord)
+ # Some Rails apps don't use ActiveRecord.
+ return unless defined?(::ActiveRecord)
+
+ # However, some dependencies might still require it, so we need an
+ # extra check. Apps that don't need ActiveRecord will likely have no
+ # AR configurations defined. We will skip APM integration in that
+ # case. See: https://github.com/airbrake/airbrake/issues/1222
+ configurations = ::ActiveRecord::Base.configurations
+ return unless configurations.any?
 
  # Send SQL queries.
  ActiveSupport::Notifications.subscribe(
@@ -43,21 +51,22 @@ def tie_activerecord_apm
  )
 
  # Filter out parameters from SQL body.
- if ::ActiveRecord::Base.respond_to?(:connection_db_config)
- # Rails 6.1+ deprecates "connection_config" in favor of
- # "connection_db_config", so we need an updated call.
- Airbrake.add_performance_filter(
- Airbrake::Filters::SqlFilter.new(
- ::ActiveRecord::Base.connection_db_config.configuration_hash[:adapter],
- ),
- )
- else
- Airbrake.add_performance_filter(
- Airbrake::Filters::SqlFilter.new(
- ::ActiveRecord::Base.connection_config[:adapter],
- ),
- )
+ sql_filter = Airbrake::Filters::SqlFilter.new(
+ detect_activerecord_adapter(configurations),
+ )
+ Airbrake.add_performance_filter(sql_filter)
+ end
+
+ # Rails 6+ introduces the `configs_for` API instead of the deprecated
+ # `#[]`, so we need an updated call.
+ def detect_activerecord_adapter(configurations)
+ unless configurations.respond_to?(:configs_for)
+ return configurations[::Rails.env]['adapter']
  end
+
+ cfg = configurations.configs_for(env_name: ::Rails.env).first
+ # Rails 7+ API : Rails 6 API.
+ cfg.respond_to?(:adapter) ? cfg.adapter : cfg.config['adapter']
  end
  end
  end