title: How do I authorize a service account for Google Calendar API in Ruby?
body: <p>How do I authorize a service account for Google Calendar API in Ruby? I tried the quick start guide, but it crashed.</p>
  
  <p><a href="https://developers.google.com/calendar/quickstart/ruby#step_3_set_up_the_sample" rel="nofollow noreferrer">https://developers.google.com/calendar/quickstart/ruby#step_3_set_up_the_sample</a></p>
  
  <code>quickstart.rb</code>
  
  <pre><code>require 'google/apis/calendar_v3'
  require 'googleauth'
  require 'googleauth/stores/file_token_store'
  require 'fileutils'
  
  OOB_URI = 'urn:ietf:wg:oauth:2.0:oob'.freeze
  APPLICATION_NAME = 'Google Calendar API Ruby Quickstart'.freeze
  CLIENT_SECRETS_PATH = 'client_secrets.json'.freeze
  CREDENTIALS_PATH = 'token.yaml'.freeze
  SCOPE = Google::Apis::CalendarV3::AUTH_CALENDAR_READONLY
  
  ##
  # Ensure valid credentials, either by restoring from the saved credentials
  # files or intitiating an OAuth2 authorization. If authorization is required,
  # the user's default browser will be launched to approve the request.
  #
  # @return [Google::Auth::UserRefreshCredentials] OAuth2 credentials
  def authorize
    client_id = Google::Auth::ClientId.from_file(CLIENT_SECRETS_PATH) ### LINE 19
    token_store = Google::Auth::Stores::FileTokenStore.new(file: CREDENTIALS_PATH)
    authorizer = Google::Auth::UserAuthorizer.new(client_id, SCOPE, token_store)
    user_id = 'default'
    credentials = authorizer.get_credentials(user_id)
    if credentials.nil?
      url = authorizer.get_authorization_url(base_url: OOB_URI)
      puts 'Open the following URL in the browser and enter the ' \
           'resulting code after authorization:\n' + url
      code = gets
      credentials = authorizer.get_and_store_credentials_from_code(
        user_id: user_id, code: code, base_url: OOB_URI
      )
    end
    credentials
  end
  
  # Initialize the API
  service = Google::Apis::CalendarV3::CalendarService.new
  service.client_options.application_name = APPLICATION_NAME
  service.authorization = authorize
  
  # Fetch the next 10 events for the user
  calendar_id = 'primary'
  response = service.list_events(calendar_id,
                                 max_results: 10,
                                 single_events: true,
                                 order_by: 'startTime',
                                 time_min: Time.now.iso8601)
  puts 'Upcoming events:'
  puts 'No upcoming events found' if response.items.empty?
  response.items.each do |event|
    start = event.start.date || event.start.date_time
    puts "- #{event.summary} (#{start})"
  end
  </code></pre>
  
  <code>Console</code>
  
  <pre><code>&gt;ruby quickstart.rb
  C:/ruby23/lib/ruby/gems/2.3.0/gems/googleauth-0.6.2/lib/googleauth/client_id.rb:97:in `from_hash': Expected top level property 'installed' or 'web' to be present. (RuntimeError)
          from C:/ruby23/lib/ruby/gems/2.3.0/gems/googleauth-0.6.2/lib/googleauth/client_id.rb:83:in `block in from_file'
          from C:/ruby23/lib/ruby/gems/2.3.0/gems/googleauth-0.6.2/lib/googleauth/client_id.rb:80:in `open'
          from C:/ruby23/lib/ruby/gems/2.3.0/gems/googleauth-0.6.2/lib/googleauth/client_id.rb:80:in `from_file'
          from quickstart.rb:19:in `authorize'
          from quickstart.rb:39:in `&lt;main&gt;'
  </code></pre>
  
  <p>The (outdated) documentation for authorizing service accounts only has examples for Java and Python.</p>
  
  <p><a href="https://developers.google.com/identity/protocols/OAuth2ServiceAccount#authorizingrequests" rel="nofollow noreferrer">https://developers.google.com/identity/protocols/OAuth2ServiceAccount#authorizingrequests</a></p>
  
  <p>Old similar question with 0 answers: <a href="https://stackoverflow.com/questions/37635873/google-calendar-api-in-ruby-using-service-account">Google Calendar API in Ruby using Service Account</a></p>