Rails 6 ActiveRecord::Base.configurations

Rails 6 changed the return value of ActiveRecord::Base.configurations to an object of ActiveRecord::DatabaseConfigurations. Before Rails 6, ActiveRecord::Base.configurations returned a hash with all the database configurations. We can call to_h on the object of ActiveRecord::DatabaseConfigurations to get a hash.

A method named configs_for has also been added on to fetch configurations for a particular environment.

Rails 5.2

>> ActiveRecord::Base.configurations

=> {"development"=>{"adapter"=>"sqlite3", "pool"=>5, "timeout"=>5000, "database"=>"db/development.sqlite3"}, "test"=>{"adapter"=>"sqlite3", "pool"=>5, "timeout"=>5000, "database"=>"db/test.sqlite3"}, "production"=>{"adapter"=>"sqlite3", "pool"=>5, "timeout"=>5000, "database"=>"db/production.sqlite3"}}

Rails 6.0.0.beta2

>> ActiveRecord::Base.configurations

=> #<ActiveRecord::DatabaseConfigurations:0x00007fc18274f9f0 @configurations=[#<ActiveRecord::DatabaseConfigurations::HashConfig:0x00007fc18274f680 @env_name="development", @spec_name="primary", @config={"adapter"=>"sqlite3", "pool"=>5, "timeout"=>5000, "database"=>"db/development.sqlite3"}>, #<ActiveRecord::DatabaseConfigurations::HashConfig:0x00007fc18274f608 @env_name="test", @spec_name="primary", @config={"adapter"=>"sqlite3", "pool"=>5, "timeout"=>5000, "database"=>"db/test.sqlite3"}>, #<ActiveRecord::DatabaseConfigurations::HashConfig:0x00007fc18274f590 @env_name="production", @spec_name="primary", @config={"adapter"=>"sqlite3", "pool"=>5, "timeout"=>5000, "database"=>"db/production.sqlite3"}>]>

>> ActiveRecord::Base.configurations.to_h

=> {"development"=>{"adapter"=>"sqlite3", "pool"=>5, "timeout"=>5000, "database"=>"db/development.sqlite3"}, "test"=>{"adapter"=>"sqlite3", "pool"=>5, "timeout"=>5000, "database"=>"db/test.sqlite3"}, "production"=>{"adapter"=>"sqlite3", "pool"=>5, "timeout"=>5000, "database"=>"db/production.sqlite3"}}

>> ActiveRecord::Base.configurations['development']

=> {"adapter"=>"sqlite3", "pool"=>5, "timeout"=>5000, "database"=>"db/development.sqlite3"}

>> ActiveRecord::Base.configurations.configs_for(env_name: "development")

=> [#<ActiveRecord::DatabaseConfigurations::HashConfig:0x00007fc18274f680 @env_name="development", @spec_name="primary", @config={"adapter"=>"sqlite3", "pool"=>5, "timeout"=>5000, "database"=>"db/development.sqlite3"}>]

Here is the relevant pull request.