[#494] Create (or use) a Rubocop for the inverse keyword needed in the associations

.rubocop.yml

@@ -2,6 +2,7 @@ require:
   - rubocop-rails
   - rubocop-rspec
   - rubocop-performance
+  - ./custom_cops/required_inverse_of_relations.rb
 
 AllCops:
   Exclude:
@@ -50,3 +51,9 @@ RSpec/NestedGroups:
 
 RSpec/MultipleExpectations:
   Max: 10
+
+CustomCops/RequiredInverseOfRelations:
+  Enabled: true
+  Include:
+    # Only Rails model files
+    - !ruby/regexp /models\//

.template/addons/custom_cops/template.rb

@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+require 'fileutils'
+
+copy_file 'custom_cops/required_inverse_of_relations.rb', mode: :preserve

custom_cops/Gemfile

@@ -0,0 +1,6 @@
+# frozen_string_literal: true
+
+source 'https://rubygems.org'
+
+gem 'rspec'
+gem 'rubocop'

custom_cops/Gemfile.lock

@@ -0,0 +1,53 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    ast (2.4.2)
+    diff-lcs (1.5.0)
+    json (2.7.1)
+    language_server-protocol (3.17.0.3)
+    parallel (1.24.0)
+    parser (3.2.2.4)
+      ast (~> 2.4.1)
+      racc
+    racc (1.7.3)
+    rainbow (3.1.1)
+    regexp_parser (2.8.3)
+    rexml (3.2.6)
+    rspec (3.12.0)
+      rspec-core (~> 3.12.0)
+      rspec-expectations (~> 3.12.0)
+      rspec-mocks (~> 3.12.0)
+    rspec-core (3.12.2)
+      rspec-support (~> 3.12.0)
+    rspec-expectations (3.12.3)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.12.0)
+    rspec-mocks (3.12.6)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.12.0)
+    rspec-support (3.12.1)
+    rubocop (1.59.0)
+      json (~> 2.3)
+      language_server-protocol (>= 3.17.0)
+      parallel (~> 1.10)
+      parser (>= 3.2.2.4)
+      rainbow (>= 2.2.2, < 4.0)
+      regexp_parser (>= 1.8, < 3.0)
+      rexml (>= 3.2.5, < 4.0)
+      rubocop-ast (>= 1.30.0, < 2.0)
+      ruby-progressbar (~> 1.7)
+      unicode-display_width (>= 2.4.0, < 3.0)
+    rubocop-ast (1.30.0)
+      parser (>= 3.2.1.0)
+    ruby-progressbar (1.13.0)
+    unicode-display_width (2.5.0)
+
+PLATFORMS
+  arm64-darwin-22
+
+DEPENDENCIES
+  rspec
+  rubocop
+
+BUNDLED WITH
+   2.4.17

custom_cops/required_inverse_of_relations.rb

@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+module CustomCops
+  class RequiredInverseOfRelations < RuboCop::Cop::Base
+    MSG = 'Use inverse_of option when defining associations to prevent avoidable SQL queries and keep models in sync.'
+
+    # Optimization: don't call `on_send` unless the method name is in this list
+    RESTRICT_ON_SEND = %i[has_many belongs_to].freeze
+    ASSOCIATION_METHODS = RESTRICT_ON_SEND.to_set
+
+    def_node_matcher :association_expression_no_arguments?, <<~PATTERN
+      (send nil? ASSOCIATION_METHODS (sym _))
+    PATTERN
+
+    def_node_matcher :association_expression_with_arguments?, <<~PATTERN
+      (send nil? ASSOCIATION_METHODS (sym _) (hash $...))
+    PATTERN
+
+    def on_send(node)
+      return add_offense(node) if association_expression_no_arguments?(node)
+
+      return unless (hash_pairs = association_expression_with_arguments?(node))
+
+      add_offense(node) unless contain_inverse_of?(hash_pairs)
+    end
+
+    private
+
+    def contain_inverse_of?(nodes)
+      pattern = RuboCop::NodePattern.new('(pair (sym :inverse_of) _)')
+
+      nodes.any? { pattern.match(_1) }
+    end
+  end
+end

custom_cops/spec/required_inverse_of_relations_spec.rb

@@ -0,0 +1,71 @@
+# frozen_string_literal: true
+
+require 'rubocop'
+require 'rubocop/rspec/support'
+require_relative '../required_inverse_of_relations'
+
+RSpec.configure do |config|
+  config.include RuboCop::RSpec::ExpectOffense
+end
+
+describe CustomCops::RequiredInverseOfRelations, :config do
+  context 'given an association expression without :inverse_of option' do
+    it 'registers an offense' do
+      expect_offense(<<~RUBY)
+        class Test
+          has_many :books
+          ^^^^^^^^^^^^^^^ Use inverse_of option when defining associations to prevent avoidable SQL queries and keep models in sync.
+        end
+      RUBY
+
+      expect_offense(<<~RUBY)
+        class Test
+          belongs_to :books
+          ^^^^^^^^^^^^^^^^^ Use inverse_of option when defining associations to prevent avoidable SQL queries and keep models in sync.
+        end
+      RUBY
+    end
+  end
+
+  context 'given an association expression with :inverse_of option' do
+    it 'registers NO offenses' do
+      expect_no_offenses(<<~RUBY)
+        class Test
+          has_many :books, inverse_of: :author
+        end
+      RUBY
+
+      expect_no_offenses(<<~RUBY)
+        class Test
+          belongs_to :author, inverse_of: :books
+        end
+      RUBY
+    end
+  end
+
+  context 'given a method which have the same name with one of Rails association helpers' do
+    context 'given the method invocation has explicit module/class' do
+      it 'registers NO offenses' do
+        expect_no_offenses(<<~RUBY)
+          class Test
+            def test
+              Module.has_many :books
+            end
+          end
+        RUBY
+      end
+    end
+
+    context 'given the method invocation has explicit receiver' do
+      it 'registers NO offenses' do
+        expect_no_offenses(<<~RUBY)
+          class Test
+            def test
+              self.has_many :books
+            end
+          end
+        RUBY
+      end
+    end
+  end
+end

template.rb

@@ -74,6 +74,9 @@ def apply_template!(template_root)
   apply '.template/variants/api/template.rb' if API_VARIANT
   apply '.template/variants/web/template.rb' if WEB_VARIANT
 
+  # Custom Rubocop cops
+  apply '.template/addons/custom_cops/template.rb'
+
   # A list necessary jobs that run before complete, ex: Fixing rubocop on Ruby files that generated by Rails
   apply '.template/hooks/before_complete/fix_rubocop.rb'
   apply '.template/hooks/before_complete/report.rb'