Add rubocop rule for ignore_column(s) usages

Prior to this change, ignore rules for a columns were defined in CE or
EE models. But if a model exists in CE and EE, the ignore rule has to
be in the CE model. If the model only exists in EE, then it has to be
added there. A new rubocop rule will check for the correct location of
the ignore rule.

rubocop/cop/ignored_columns.rb

@@ -4,16 +4,50 @@ module RuboCop
   module Cop
     # Cop that blacklists the usage of Group.public_or_visible_to_user
     class IgnoredColumns < RuboCop::Cop::Cop
-      MSG = 'Use `IgnoredColumns` concern instead of adding to `self.ignored_columns`.'
+      USE_CONCERN_MSG = 'Use `IgnoredColumns` concern instead of adding to `self.ignored_columns`.'
+      WRONG_MODEL_MSG = 'If the model exists in CE and EE, the column has to be ignored ' \
+        'in the CE model. If the model only exists in EE, then it has to be added there.'
 
       def_node_matcher :ignored_columns?, <<~PATTERN
         (send (self) :ignored_columns)
       PATTERN
 
+      def_node_matcher :ignore_columns?, <<~PATTERN
+        (send nil? :ignore_columns ...)
+      PATTERN
+
+      def_node_matcher :ignore_column?, <<~PATTERN
+        (send nil? :ignore_column ...)
+      PATTERN
+
       def on_send(node)
-        return unless ignored_columns?(node)
+        if ignored_columns?(node)
+          add_offense(node, location: :expression, message: USE_CONCERN_MSG)
+        end
+
+        if concern_usage?(node) && used_in_wrong_model?
+          add_offense(node, location: :expression, message: WRONG_MODEL_MSG)
+        end
+      end
+
+      private
+
+      def concern_usage?(node)
+        ignore_columns?(node) || ignore_column?(node)
+      end
+
+      def used_in_wrong_model?
+        file_path = processed_source.file_path
+
+        ee_model?(file_path) && ce_model_exists?(file_path)
+      end
+
+      def ee_model?(path)
+        path.include?('ee/')
+      end
 
-        add_offense(node, location: :expression)
+      def ce_model_exists?(path)
+        File.exist?(path.gsub(%r{ee/}, ''))
       end
     end
   end

spec/rubocop/cop/ignored_columns_spec.rb

@@ -14,4 +14,84 @@ RSpec.describe RuboCop::Cop::IgnoredColumns do
       end
     RUBY
   end
+
+  context 'when only CE model exist' do
+    let(:file_path) { full_path('app/models/bar.rb') }
+
+    it 'does not flag ignore_columns usage in CE model' do
+      expect_no_offenses(<<~RUBY, file_path)
+        class Bar < ApplicationRecord
+          ignore_columns :foo, remove_with: '14.3', remove_after: '2021-09-22'
+        end
+      RUBY
+    end
+
+    it 'flags ignore_column usage in EE model' do
+      expect_no_offenses(<<~RUBY, file_path)
+        class Baz < ApplicationRecord
+          ignore_column :bar, remove_with: '14.3', remove_after: '2021-09-22'
+        end
+      RUBY
+    end
+  end
+
+  context 'when only EE model exist' do
+    let(:file_path) { full_path('ee/app/models/ee/bar.rb') }
+
+    before do
+      allow(File).to receive(:exist?).with(full_path('app/models/bar.rb')).and_return(false)
+    end
+
+    it 'flags ignore_columns usage in EE model' do
+      file_path = full_path('ee/app/models/ee/bar.rb')
+
+      expect_no_offenses(<<~RUBY, file_path)
+        class Bar < ApplicationRecord
+          ignore_columns :foo, remove_with: '14.3', remove_after: '2021-09-22'
+        end
+      RUBY
+    end
+
+    it 'flags ignore_column usage in EE model' do
+      expect_no_offenses(<<~RUBY, file_path)
+        class Bar < ApplicationRecord
+          ignore_column :foo, remove_with: '14.3', remove_after: '2021-09-22'
+        end
+      RUBY
+    end
+  end
+
+  context 'when CE and EE model exist' do
+    let(:file_path) { full_path('ee/app/models/ee/bar.rb') }
+
+    before do
+      allow(File).to receive(:exist?).with(full_path('app/models/bar.rb')).and_return(true)
+    end
+
+    it 'flags ignore_columns usage in EE model' do
+      expect_offense(<<~RUBY, file_path)
+        class Bar < ApplicationRecord
+          ignore_columns :foo, remove_with: '14.3', remove_after: '2021-09-22'
+          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ If the model exists in CE and EE, [...]
+        end
+      RUBY
+    end
+
+    it 'flags ignore_column usage in EE model' do
+      expect_offense(<<~RUBY, file_path)
+        class Bar < ApplicationRecord
+          ignore_column :foo, remove_with: '14.3', remove_after: '2021-09-22'
+          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ If the model exists in CE and EE, [...]
+        end
+      RUBY
+    end
+  end
+
+  private
+
+  def full_path(path)
+    rails_root = '../../../../'
+
+    File.expand_path(File.join(rails_root, path), __dir__)
+  end
 end