Upgrade rubocop

Rakefile

@@ -1,29 +1,33 @@
+# frozen_string_literal: true
+
 require 'rake'
 require 'rake/testtask'
-$LOAD_PATH.unshift File.expand_path("../lib", __FILE__)
-require "liquid/version"
+$LOAD_PATH.unshift(File.expand_path('lib', __dir__))
+require 'liquid/version'
 
-task default: [:test, :rubocop]
+task(default: %i[test rubocop])
 
-desc 'run test suite with default parser'
+desc('run test suite with default parser')
 Rake::TestTask.new(:base_test) do |t|
   t.libs << '.' << 'lib' << 'test'
   t.test_files = FileList['test/{integration,unit}/**/*_test.rb']
   t.verbose = false
 end
 
-desc 'run test suite with warn error mode'
+desc('run test suite with warn error mode')
 task :warn_test do
   ENV['LIQUID_PARSER_MODE'] = 'warn'
   Rake::Task['base_test'].invoke
 end
 
 task :rubocop do
-  require 'rubocop/rake_task'
-  RuboCop::RakeTask.new
+  if RUBY_ENGINE == 'ruby'
+    require 'rubocop/rake_task'
+    RuboCop::RakeTask.new
+  end
 end
 
-desc 'runs test suite with both strict and lax parsers'
+desc('runs test suite with both strict and lax parsers')
 task :test do
   ENV['LIQUID_PARSER_MODE'] = 'lax'
   Rake::Task['base_test'].invoke
@@ -32,8 +36,9 @@ task :test do
   Rake::Task['base_test'].reenable
   Rake::Task['base_test'].invoke
 
-  if RUBY_ENGINE == 'ruby'
-    ENV['LIQUID-C'] = '1'
+  if RUBY_ENGINE == 'ruby' || RUBY_ENGINE == 'truffleruby'
+
+    ENV['LIQUID_C'] = '1'
 
     ENV['LIQUID_PARSER_MODE'] = 'lax'
     Rake::Task['base_test'].reenable
@@ -45,9 +50,9 @@ task :test do
   end
 end
 
-task gem: :build
+task(gem: :build)
 task :build do
-  system "gem build liquid.gemspec"
+  system 'gem build liquid.gemspec'
 end
 
 task install: :build do
@@ -56,45 +61,45 @@ end
 
 task release: :build do
   system "git tag -a v#{Liquid::VERSION} -m 'Tagging #{Liquid::VERSION}'"
-  system "git push --tags"
+  system 'git push --tags'
   system "gem push liquid-#{Liquid::VERSION}.gem"
   system "rm liquid-#{Liquid::VERSION}.gem"
 end
 
 namespace :benchmark do
-  desc "Run the liquid benchmark with lax parsing"
+  desc 'Run the liquid benchmark with lax parsing'
   task :run do
-    ruby "./performance/benchmark.rb lax"
+    ruby './performance/benchmark.rb lax'
   end
 
-  desc "Run the liquid benchmark with strict parsing"
+  desc 'Run the liquid benchmark with strict parsing'
   task :strict do
-    ruby "./performance/benchmark.rb strict"
+    ruby './performance/benchmark.rb strict'
   end
 end
 
 namespace :profile do
-  desc "Run the liquid profile/performance coverage"
+  desc 'Run the liquid profile/performance coverage'
   task :run do
-    ruby "./performance/profile.rb"
+    ruby './performance/profile.rb'
   end
 
-  desc "Run the liquid profile/performance coverage with strict parsing"
+  desc 'Run the liquid profile/performance coverage with strict parsing'
   task :strict do
-    ruby "./performance/profile.rb strict"
+    ruby './performance/profile.rb strict'
   end
 end
 
 namespace :memory_profile do
-  desc "Run memory profiler"
+  desc 'Run memory profiler'
   task :run do
-    ruby "./performance/memory_profile.rb"
+    ruby './performance/memory_profile.rb'
   end
 end
 
-desc "Run example"
+desc('Run example')
 task :example do
-  ruby "-w -d -Ilib example/server/server.rb"
+  ruby '-w -d -Ilib example/server/server.rb'
 end
 
 task :console do