A query printer for GraphQL-Ruby that redacts strings

query_printer.rb

# frozen_string_literal: true


# QueryPrinter is a custom GraphQL Ruby
# printer used to print sanitized queries. It inlines provided variables
# within the query for facilitate logging and analysis of queries.
# The printer assumes the query is valid.
#
# Since the GraphQL Ruby AST for a GraphQL query doesnt contain any reference
# on the type of fields or arguments, we have to track the current object, field
# and input type while printing the query.
#
# @example Printing a scrubbed string 
#   printer = QueryPrinter.new(query) 
#   puts printer.scrubbed 
#
class QueryPrinter < GraphQL::Language::Printer
  class InvalidQueryError < ArgumentError; end

  REDACTED = "<REDACTED>"

  def initialize(query)
    @query = query
    @current_type = nil
    @current_field = nil
    @current_input_type = nil
  end
  
  # @return [String] A scrubbed query string 
  def scrubbed
    raise InvalidQueryError, "Printing requires a valid GraphQL query." unless query.valid? # rubocop:disable GitHub/UsePlatformErrors

    print(query.document)
  end

  def print_node(node, indent: "")
    # Replace any strings that aren't IDs or Enum values with REDACTED
    if node.is_a?(String) && !(type.kind.enum? || type == GraphQL::ID_TYPE)
      GraphQL::Language.serialize(REDACTED)
    elsif node.is_a?(Array)
      old_input_type = @current_input_type
      if @current_input_type && @current_input_type.list?
        @current_input_type = @current_input_type.of_type
        @current_input_type = @current_input_type.of_type if @current_input_type.non_null?
      end

      res = super
      @current_input_type = old_input_type
      res
    else
      super
    end
  end

  def print_argument(argument)
    arg_def = if @current_input_type
      @current_input_type.arguments[argument.name]
    elsif @current_directive
      @current_directive.arguments[argument.name]
    else
      @current_field.arguments[argument.name]
    end

    old_input_type = @current_input_type
    @current_input_type = arg_def.type.non_null? ? arg_def.type.of_type : arg_def.type
    res = super
    @current_input_type = old_input_type
    res
  end

  def print_list_type(list_type)
    old_input_type = @current_input_type
    @current_input_type = old_input_type.of_type
    res = super
    @current_input_type = old_input_type
    res
  end

  def print_variable_identifier(variable_id)
    variable_value = query.provided_variables.with_indifferent_access[variable_id.name]
    print_node(VariableInliner.new(variable_value, @current_input_type).to_ast)
  end

  def print_field(field, indent: "")
    @current_field = query.schema.get_field(@current_type, field.name)
    old_type = @current_type
    @current_type = @current_field.type.unwrap
    res = super
    @current_type = old_type
    res
  end

  def print_input_object(input_object)
    printed_arguments = input_object.arguments.map do |a|
      print_argument(a)
    end

    "{#{printed_arguments.join(", ")}}"
  end

  def print_inline_fragment(inline_fragment, indent: "")
    old_type = @current_type

    if inline_fragment.type
      @current_type = query.schema.types[inline_fragment.type.name]
    end

    res = super

    @current_type = old_type

    res
  end

  def print_fragment_definition(fragment_def, indent: "")
    old_type = @current_type
    @current_type = query.schema.types[fragment_def.type.name]

    res = super

    @current_type = old_type

    res
  end

  def print_directive(directive)
    @current_directive = query.schema.directives[directive.name]

    res = super

    @current_directive = nil
    res
  end

  # Print the operation definition but do not include the variable
  # definitions since we will inline them within the query
  def print_operation_definition(operation_definition, indent: "")
    old_type = @current_type
    @current_type = query.schema.public_send(operation_definition.operation_type)

    out = "#{indent}#{operation_definition.operation_type}".dup
    out << " #{operation_definition.name}" if operation_definition.name
    out << print_directives(operation_definition.directives)
    out << print_selections(operation_definition.selections, indent: indent)

    @current_type = old_type
    out
  end

  private

  attr_reader :query
end