google-auth-library-ruby/lib/googleauth/application_default.rb

# Copyright 2015, Google Inc.
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require 'googleauth/compute_engine'
require 'googleauth/default_credentials'

module Google
  # Module Auth provides classes that provide Google-specific authorization
  # used to access Google APIs.
  module Auth
    NOT_FOUND_ERROR = <<ERROR_MESSAGE.freeze
Could not load the default credentials. Browse to
https://developers.google.com/accounts/docs/application-default-credentials
for more information
ERROR_MESSAGE

    # Obtains the default credentials implementation to use in this
    # environment.
    #
    # Use this to obtain the Application Default Credentials for accessing
    # Google APIs.  Application Default Credentials are described in detail
    # at http://goo.gl/IUuyuX.
    #
    # If supplied, scope is used to create the credentials instance, when it can
    # be applied.  E.g, on google compute engine and for user credentials the
    # scope is ignored.
    #
    # @param scope [string|array|nil] the scope(s) to access
    # @param options [hash] allows override of the connection being used
    def get_application_default(scope = nil, options = {})
      creds = DefaultCredentials.from_env(scope) ||
              DefaultCredentials.from_well_known_path(scope) ||
              DefaultCredentials.from_system_default_path(scope)
      return creds unless creds.nil?
      unless GCECredentials.on_gce?(options)
        # Clear cache of the result of GCECredentials.on_gce?
        GCECredentials.unmemoize_all
        raise NOT_FOUND_ERROR
      end
      GCECredentials.new
    end

    module_function :get_application_default
  end
end