Introduce rubocop-thread_safety and fix issues

Author: KieranP

.rubocop.yml

@@ -8,6 +8,7 @@ require:
   - rubocop-rspec_rails
   - rubocop-factory_bot
   - rubocop-obsession
+  - rubocop-thread_safety
 
 AllCops:
   NewCops: enable

Gemfile

@@ -57,6 +57,7 @@ group :development do
   gem 'rubocop-rspec_rails', require: false
   gem 'rubocop-factory_bot', require: false
   gem 'rubocop-obsession', require: false
+  gem 'rubocop-thread_safety', require: false
   gem 'bundler-audit', require: false
   gem 'brakeman', require: false
   gem 'lefthook', require: false

Gemfile.lock

@@ -367,6 +367,8 @@ GEM
       rubocop-rspec (~> 3, >= 3.0.1)
     rubocop-shopify (2.15.1)
       rubocop (~> 1.51)
+    rubocop-thread_safety (0.5.1)
+      rubocop (>= 0.90.0)
     ruby-progressbar (1.13.0)
     ruby_parser (3.21.1)
       racc (~> 1.5)
@@ -465,6 +467,7 @@ DEPENDENCIES
   rubocop-rspec
   rubocop-rspec_rails
   rubocop-shopify
+  rubocop-thread_safety
   selenium-webdriver
   simplecov
   solid_queue

app/graphql/concerns/object_helpers.rb

@@ -5,7 +5,8 @@ module ObjectHelpers
 
   class_methods do
     def model
-      @model ||= name.demodulize.constantize
+      Thread.current["#{name}.model"] ||=
+        name.demodulize.constantize
     end
 
     def association(association, ...)

app/graphql/objects/base.rb

@@ -7,20 +7,22 @@ class Base < GraphQL::Schema::Object
     include ObjectHelpers
 
     class << self
-      def policy(policy)
-        @policy = policy
+      def policy(policy = nil)
+        Thread.current["#{name}.policy"] ||= policy
       end
 
       def authorized?(obj, ctx)
         super && pundit_authorized?(obj, ctx)
       end
 
       def pundit_authorized?(obj, ctx)
-        return true unless @policy
+        return true unless policy
 
         user = ctx[:current_user]
-        policy = Pundit.policy(user, obj)
-        policy.send(@policy)
+
+        Pundit
+          .policy(user, obj)
+          .send(policy)
       end
     end
   end