feature_flags.rb

# app/utils/feature_flags.rb
module FeatureFlags
  module Instrumentation
    module_function

    DEFAULT_ERROR_MESSAGE = 'This Feature is currently unavailable, please try again later.'

    def before_query(query)
      # We query for the root fields alone.
      begin
        # We do not try to select them uniquely because queries can differ in some form of arguments passed to them.
        root_fields = query.selected_operation.selections.map { |s| s }
      rescue
        root_fields = []
      end
      root_fields.each do |field|
        check_flags(field)
      end
    end

    def after_query(query)
      # ...
    end

    def check_flags(field)
      case field.name
      when "queryFoo"
        unless Flipper["Foo"].enabled?
          raise GraphQL::ExecutionError.new(DEFAULT_ERROR_MESSAGE)  
        end
        
        # carry on with the query action.  
        # ...
    end
    
    # This is used to get the GraphQL operation name. 
    def get_operation_name(field, name) 
      operation_index = field.arguments.index { |arg| arg.name == name }
      operation_name = field.arguments[operation_index].value
    end
  end

end