Quick way to use ENVs from Heroku config while using Rails 5.2 style credentials for development.

app_config.rb

module AppConfig
  def self.get(key)
    env_val = ENV[key.to_s]
    return env_val if env_val.present?

    rails_credentials = Rails.application.credentials

    # Tries finding a key with the first part being nested first.
    # :aws_access_key_id will attempt to grab
    # { aws: { access_key_id: 'val' } }
    # before attempting
    # { aws_access_key_id: 'val' }

    rails_credentials.dig(*key.to_s.split("_", 2).map(&:to_sym)) ||
      rails_credentials.dig(key.to_sym)
  end
end

Potential clash with local ENVs, I can always do an environment check explicitly instead of always checking ENV first.