resolve_symbol_connection

# File activerecord/lib/active_record/database_configurations.rb, line 173
      def resolve_symbol_connection(name)
        if db_config = find_db_config(name)
          db_config
        else
          raise AdapterNotSpecified, <<~MSG
            The `#{name}` database is not configured for the `#{default_env}` environment.

              Available database configurations are:

              #{build_configuration_sentence}
          MSG
        end
      end

      def build_configuration_sentence
        configs = configs_for(include_hidden: true)

        configs.group_by(&:env_name).map do |env, config|
          names = config.map(&:name)
          if names.size > 1
            "#{env}: #{names.join(", ")}"
          else
            env
          end
        end.join("\n")
      end

      def build_db_config_from_raw_config(env_name, name, config)
        case config
        when String
          build_db_config_from_string(env_name, name, config)
        when Hash
          build_db_config_from_hash(env_name, name, config.symbolize_keys)
        else
          raise InvalidConfigurationError, "'{ #{env_name} => #{config} }' is not a valid configuration. Expected '#{config}' to be a URL string or a Hash."
        end
      end

      def build_db_config_from_string(env_name, name, config)
        url = config
        uri = URI.parse(url)
        if uri.scheme
          UrlConfig.new(env_name, name, url)
        else
          raise InvalidConfigurationError, "'{ #{env_name} => #{config} }' is not a valid configuration. Expected '#{config}' to be a URL string or a Hash."
        end
      end

      def build_db_config_from_hash(env_name, name, config)
        if config.has_key?(:url)
          url = config[:url]
          config_without_url = config.dup
          config_without_url.delete :url

          UrlConfig.new(env_name, name, url, config_without_url)
        else
          HashConfig.new(env_name, name, config)
        end
      end

      def merge_db_environment_variables(current_env, configs)
        configs.map do |config|
          next config if config.is_a?(UrlConfig) || config.env_name != current_env

          url_config = environment_url_config(current_env, config.name, config.configuration_hash)
          url_config || config
        end
      end

      def environment_url_config(env, name, config)
        url = environment_value_for(name)
        return unless url

        UrlConfig.new(env, name, url, config)
      end

      def environment_value_for(name)
        name_env_key = "#{name.upcase}_DATABASE_URL"
        url = ENV[name_env_key]
        url ||= ENV["DATABASE_URL"] if name == "primary"
        url
      end
  end