Support conditions option of UniquenessValidator

Since the `:conditions` option is a callable, we can't know exactly
which columns are necessary for the index, and the index is not required
to be unique anymore (maybe the conditions make the uniqueness only
apply to some records), it's not possible to add an offense when the
option is used.

Author: etiennebarrie

changelog/fix_support_conditions_option_of.md

@@ -0,0 +1 @@
+* [#882](https://github.com/rubocop/rubocop-rails/pull/882): Fix false positive for `Rails/UniqueValidationWithoutIndex` with :conditions option. ([@etiennebarrie][])

lib/rubocop/cop/rails/unique_validation_without_index.rb

@@ -139,20 +139,20 @@ def condition_part?(node)
           pairs = node.arguments.last
           return unless pairs.hash_type?
 
-          return true if condition_hash_part?(pairs)
+          return true if condition_hash_part?(pairs, keys: %i[if unless])
 
           uniqueness_node = uniqueness_part(node)
           return unless uniqueness_node&.hash_type?
 
-          condition_hash_part?(uniqueness_node)
+          condition_hash_part?(uniqueness_node, keys: %i[if unless conditions])
         end
 
-        def condition_hash_part?(pairs)
+        def condition_hash_part?(pairs, keys:)
           pairs.each_pair.any? do |pair|
             key = pair.key
             next unless key.sym_type?
 
-            key.value == :if || key.value == :unless
+            keys.include?(key.value)
           end
         end
 

spec/rubocop/cop/rails/unique_validation_without_index_spec.rb

@@ -371,6 +371,16 @@ class Article
             end
           RUBY
         end
+
+        it 'does not register an offense with a conditions option on the specific validator' do
+          expect_no_offenses(<<~RUBY)
+            class Article
+              belongs_to :user
+              enum :status, [:draft, :published]
+              validates :user, uniqueness: { conditions: -> { published } }
+            end
+          RUBY
+        end
       end
 
       context 'without column definition' do