Merge pull request #601 from tachyons/bugfix/handle_ignored_columns_from_mixins

Handle ignored_columns from mixins

Author: koic

changelog/fix_handle_ignored_columns_from_mixins.md

@@ -0,0 +1 @@
+* [#601](https://github.com/rubocop/rubocop-rails/pull/601): Handle ignored_columns from mixins for `Rails/UnusedIgnoredColumns` cop. ([@tachyons][])

lib/rubocop/cop/rails/unused_ignored_columns.rb

@@ -61,6 +61,8 @@ def class_node(node)
 
         def table(node)
           klass = class_node(node)
+          return unless klass
+
           schema.table_by(name: table_name(klass))
         end
       end

spec/rubocop/cop/rails/unused_ignored_columns_spec.rb

@@ -33,6 +33,16 @@ class User < ApplicationRecord
       end
     end
 
+    context 'with an used/unused ignored column in a mixin' do
+      it 'does nothing' do
+        expect_no_offenses(<<~RUBY)
+          module Abc
+            self.ignored_columns = [:real_name]
+          end
+        RUBY
+      end
+    end
+
     context 'with an unused ignored column as a String' do
       it 'registers an offense' do
         expect_offense(<<~RUBY)