Fix an error for Rails/UniqBeforePluck with EnforcedStyle: aggressive when no receiver

changelog/fix_an_error_for_rails_uniq_before_pluck.md

@@ -0,0 +1 @@
+* [#1255](https://github.com/rubocop/rubocop-rails/pull/1255): Fix an error for `Rails/UniqBeforePluck` with `EnforcedStyle: aggressive` when no receiver. ([@earlopain][])

lib/rubocop/cop/rails/uniq_before_pluck.rb

@@ -68,15 +68,23 @@ def on_send(node)
           return unless uniq
 
           add_offense(node.loc.selector) do |corrector|
-            method = node.method_name
-
-            corrector.remove(dot_method_with_whitespace(method, node))
-            corrector.insert_before(node.receiver.loc.dot.begin, '.distinct')
+            autocorrect(corrector, node)
           end
         end
 
         private
 
+        def autocorrect(corrector, node)
+          method = node.method_name
+
+          corrector.remove(dot_method_with_whitespace(method, node))
+          if (dot = node.receiver.loc.dot)
+            corrector.insert_before(dot.begin, '.distinct')
+          else
+            corrector.insert_before(node.receiver, 'distinct.')
+          end
+        end
+
         def dot_method_with_whitespace(method, node)
           range_between(dot_method_begin_pos(method, node), node.loc.selector.end_pos)
         end

spec/rubocop/cop/rails/uniq_before_pluck_spec.rb

@@ -113,5 +113,16 @@
         instance.assoc.distinct.pluck(:name)
       RUBY
     end
+
+    it 'corrects uniq when used without a receiver' do
+      expect_offense(<<~RUBY)
+        pluck(:name).uniq
+                     ^^^^ Use `distinct` before `pluck`.
+      RUBY
+
+      expect_correction(<<~RUBY)
+        distinct.pluck(:name)
+      RUBY
+    end
   end
 end