Can't use `#to_param` as a field any more

[tomek-ac]

Below is a piece of code that used to work fine until v0.16.0 and stopped since v0.17.0. Tested with Ruby 3.2.2.

We use similar code to make the objects returned from GraphQL queries work with Rails' route helpers and for that we need to add #to_param to our type definitions.

In a Rails project #to_param is defined on the base Object class and by default returns self.to_s (source).

The objects returned from queries inherit from GraphQL::Client::Schema::ObjectClass which inherits from Object. So when we call #to_param on an object returned from the query it gets dispatched as Object#to_param and doesn't end up in GraphQL::Client::Schema::ObjectClass#method_missing. Thus instead of IDs of records we get strings like "#<#<Module:0x00000001062529f0>::User:0x0000000106316d50>".

It looks that in v0.16.0 all the typed fields were defined as methods on the query objects and since v0.17.0 the library moved to method_missing dispatch. That's why it's no longer possible to use fields that correspond to instance methods of Object, like #to_param.

#!/usr/bin/env ruby
require "bundler/inline"
gemfile do
  source "https://rubygems.org"

  gem "graphql", "1.13.2"
  # gem "graphql-client", "0.16.0" # <--- this works as expected
  gem "graphql-client", "0.21.0"
  gem "activesupport", "7.1.3.2"
end
require "graphql"
require "graphql/client"
require "active_support/core_ext/object/to_query"

module MyData
  User = Data.define(:id)
end

module MyTypes
  class User < GraphQL::Schema::Object
    field :id, ID, null: false
    field :to_param, String, null: false, resolver_method: :resolve_to_param

    def resolve_to_param
      "user-#{object.id}"
    end
  end

  class Query < GraphQL::Schema::Object
    field :current_user, User, null: false

    def current_user
      MyData::User.new(id: 1)
    end
  end
end

class MySchema < GraphQL::Schema
  query(MyTypes::Query)
end

client = GraphQL::Client.new(schema: MySchema, execute: MySchema)

TEST_QUERY = client.parse(<<~GRAPHQL)
  query {
    currentUser {
      toParam
    }
  }
GRAPHQL

current_user = client.query(TEST_QUERY).data.current_user

puts "current_user is #{current_user.inspect}"
puts "Expecting #to_param to return \"user-1\", got: #{current_user.to_param.inspect}"