Error Instrumentation

error_instrumentation.rb

# frozen_string_literal: true
class ErrorInstrumentation
  def instrument(type, field)
    old_resolver = field.resolve_proc
    new_resolver = -> (obj, args, ctx) do
      begin # rubocop:disable Style/RedundantBegin
        result = old_resolver.call(obj, args, ctx)

        if result.is_a?(StandardError)
          set_error_context(result, type, obj, field, args, ctx)
        elsif result.is_a?(Promise)
          result.rescue do |error|
            set_error_context(error, type, obj, field, args, ctx)
            raise error
          end

          result = result.then do |next_result|
            set_error_context(next_result, type, obj, field, args, ctx) if next_result.is_a?(StandardError)
            next_result
          end
        end

        result
      rescue => ex
        set_error_context(ex, type, obj, field, args, ctx)
        raise
      end
    end

    field.redefine { resolve(new_resolver) }
  end

  def set_error_context(exception, graphql_type, object, field_definition, args, context)
    object_path = { 'type' => object.class.name }

    begin
      object_path['id'] = object.id if object.respond_to?(:id)
      object_path['gid'] = object.gid if object.respond_to?(:gid)
    rescue # rubocop:disable Lint/HandleExceptions
      # noop
    end

    error_context = exception.instance_variable_get(:@_graphql_error_context)

    if error_context
      error_context['object_path'] = Array.wrap(error_context['object_path'])
      error_context['object_path'].unshift(object_path)
    else
      error_context = {
        'graphql_type' => graphql_type.name,
        'field' => field_definition.name,
        'args' => args.to_h,
        'path' => context.path,
        'object' => object_path,
      }

      exception.instance_variable_set(:@_graphql_error_context, error_context)
    end
  end
end