[SOLVED] How to set the complexity of _

How to set the complexity of __typename in graphql-ruby

In a Rails application using the graphql-ruby gem, how do I make it so that the __typename does not add up to the complexity of the query?

By default, the complexity of all fields is 1, but I want to override it (customize it) so that it's 0.

We are tweaking our complexity calculation and we are trying to make all scalar fields cost 0. How do I do that?

Solution

I ended up creating a child class of DynamicFields where I can override the complexity of the typename field.

# Redefines DynamicFields to set a custom complexity to the __typename field.
# This module is then used in the schema definition.
#
# Doc:
# https://graphql-ruby.org/schema/introspection#extending-a-built-in-type
#
# Original:
# https://github.com/rmosolgo/graphql-ruby/blob/master/lib/graphql/introspection/dynamic_fields.rb

module Introspection
  class DynamicFields < GraphQL::Introspection::DynamicFields
    field :__typename, String, null: false, complexity: 0, description: 'The name of this type'
  end
end

And then I had to use the introspection keyword to use it:

class MySchema < GraphQL::Schema
  introspection(Introspection)
end

Reference: https://graphql-ruby.org/schema/introspection#extending-a-built-in-type