[Fix rubocop#1189] Fix false negatives for Rails/Pluck

Fixes rubocop#1189.

This PR fixes false negatives for `Rails/Pluck`
when using safe navigation method calls.

changelog/fix_false_negatives_for_rails_pluck.md

@@ -0,0 +1 @@
+* [#1189](https://github.com/rubocop/rubocop-rails/issues/1189): Fix false negatives for `Rails/Pluck` when using safe navigation method calls. ([@koic][])

lib/rubocop/cop/rails/pluck.rb

@@ -38,7 +38,7 @@ class Pluck < Base
         minimum_target_rails_version 5.0
 
         def_node_matcher :pluck_candidate?, <<~PATTERN
-          ({block numblock} (send _ {:map :collect}) $_argument (send lvar :[] $_key))
+          ({block numblock} (call _ {:map :collect}) $_argument (send lvar :[] $_key))
         PATTERN
 
         def on_block(node)

spec/rubocop/cop/rails/pluck_spec.rb

@@ -42,6 +42,19 @@
         end
       end
 
+      context "when safe navigation `#{method}` with method call key can be replaced with `pluck`" do
+        it 'registers an offense' do
+          expect_offense(<<~RUBY, method: method)
+            x&.%{method} { |a| a[obj.do_something] }
+               ^{method}^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Prefer `pluck(obj.do_something)` over `%{method} { |a| a[obj.do_something] }`.
+          RUBY
+
+          expect_correction(<<~RUBY)
+            x&.pluck(obj.do_something)
+          RUBY
+        end
+      end
+
       context 'when the block argument is unused' do
         it 'does not register an offense' do
           expect_no_offenses(<<~RUBY)