add graphql types and a test

i expected the test to generate SQL queries like:
  User Load (0.1ms)  SELECT "users".* FROM "users" LIMIT ?  [["LIMIT", 2]]
  Post Load (0.1ms)  SELECT "posts".* FROM "posts" WHERE "posts"."user_id" IN (?, ?)  [["user_id", 1], ["user_id", 2]]
  Post Load (0.1ms)  SELECT "posts".* FROM "posts" WHERE "posts"."user_id" = ?  [["user_id", 1]]
  Post Load (0.1ms)  SELECT "posts".* FROM "posts" WHERE "posts"."user_id" = ?  [["user_id", 2]]

which would reproduce the bug in Shopify/graphql-batch#114, but instead i got:
  User Load (0.1ms)  SELECT "users".* FROM "users" LIMIT ?  [["LIMIT", 2]]
  Post Load (0.1ms)  SELECT "posts".* FROM "posts" WHERE "posts"."user_id" IN (?, ?)  [["user_id", 1], ["user_id", 2]]

which is correct. going to try downgrading versions / changing the association loader to see why i can't reproduce in this test repo

Gemfile.lock

@@ -72,8 +72,8 @@ GEM
     globalid (0.4.2)
       activesupport (>= 4.2.0)
     graphql (1.11.6)
-    graphql-batch (0.3.9)
-      graphql (>= 0.8, < 2)
+    graphql-batch (0.4.3)
+      graphql (>= 1.3, < 2)
       promise.rb (~> 0.7.2)
     i18n (1.8.5)
       concurrent-ruby (~> 1.0)

app/graphql/association_loader.rb

@@ -0,0 +1,48 @@
+class AssociationLoader < GraphQL::Batch::Loader
+  def self.validate(model, association_name)
+    new(model, association_name)
+    nil
+  end
+
+  def initialize(model, association_name)
+    @model = model
+    @association_name = association_name
+    validate
+  end
+
+  def load(record)
+    raise TypeError, "#{@model} loader can't load association for #{record.class}" unless record.is_a?(@model)
+    return Promise.resolve(read_association(record)) if association_loaded?(record)
+    super
+  end
+
+  # We want to load the associations on all records, even if they have the same id
+  def cache_key(record)
+    record.object_id
+  end
+
+  def perform(records)
+    preload_association(records)
+    records.each { |record| fulfill(record, read_association(record)) }
+  end
+
+  private
+
+  def validate
+    unless @model.reflect_on_association(@association_name)
+      raise ArgumentError, "No association #{@association_name} on #{@model}"
+    end
+  end
+
+  def preload_association(records)
+    ::ActiveRecord::Associations::Preloader.new.preload(records, @association_name)
+  end
+
+  def read_association(record)
+    record.public_send(@association_name)
+  end
+
+  def association_loaded?(record)
+    record.association(@association_name).loaded?
+  end
+end

app/graphql/record_loader.rb

@@ -0,0 +1,25 @@
+class RecordLoader < GraphQL::Batch::Loader
+  def initialize(model, column: model.primary_key, where: nil)
+    @model = model
+    @column = column.to_s
+    @column_type = model.type_for_attribute(@column)
+    @where = where
+  end
+
+  def load(key)
+    super(@column_type.cast(key))
+  end
+
+  def perform(keys)
+    query(keys).each { |record| fulfill(record.public_send(@column), record) }
+    keys.each { |key| fulfill(key, nil) unless fulfilled?(key) }
+  end
+
+  private
+
+  def query(keys)
+    scope = @model
+    scope = scope.where(@where) if @where
+    scope.where(@column => keys)
+  end
+end

app/graphql/schema.rb

@@ -0,0 +1,7 @@
+require 'graphql/batch'
+
+class Schema < GraphQL::Schema
+  query Types::QueryType
+
+  use GraphQL::Batch
+end

app/graphql/types/post_type.rb

@@ -0,0 +1,12 @@
+module Types
+  class PostType < Types::BaseObject
+    field :id, ID, null: false
+    field :created_at, GraphQL::Types::ISO8601DateTime, null: false
+    field :updated_at, GraphQL::Types::ISO8601DateTime, null: false
+
+    field :user, Types::UserType, null: true
+    def user
+      AssociationLoader.for(Post, :user).load(object)
+    end
+  end
+end

app/graphql/types/query_type.rb

@@ -3,11 +3,9 @@ class QueryType < Types::BaseObject
     # Add root-level fields here.
     # They will be entry points for queries on your schema.
 
-    # TODO: remove me
-    field :test_field, String, null: false,
-      description: "An example field added by the generator"
-    def test_field
-      "Hello World!"
+    field :users, Types::UserType.connection_type, null: false
+    def users
+      User.all
     end
   end
 end

app/graphql/types/user_type.rb

@@ -0,0 +1,13 @@
+module Types
+  class UserType < Types::BaseObject
+    field :id, ID, null: false
+    field :created_at, GraphQL::Types::ISO8601DateTime, null: false
+    field :updated_at, GraphQL::Types::ISO8601DateTime, null: false
+
+    field :posts, Types::PostType.connection_type, null: true
+    def posts
+      # object.posts
+      AssociationLoader.for(User, :posts).load(object)
+    end
+  end
+end

spec/graphql/query_spec.rb

@@ -0,0 +1,30 @@
+require 'rails_helper'
+
+RSpec.describe 'Query tests' do
+  def execute_query(query)
+    Schema.execute(
+      query,
+      variables: {},
+      context: {},
+    ).to_h.with_indifferent_access
+  end
+
+  it 'something' do
+    FactoryBot.create(:post)
+    FactoryBot.create(:post)
+
+    query = <<~GRAPHQL
+      query {
+        users(first: 2) {
+          nodes {
+            posts {
+             nodes { id }
+            }
+          }
+        }
+      }
+    GRAPHQL
+
+    p execute_query(query)
+  end
+end