[Fix rubocop#1121] Fix an error for Rails/SelectMap

Fixes rubocop#1121.

This PR fixes an error for `Rails/SelectMap`
when using `select(:column_name).map(&:column_name)` without receiver model.

changelog/fix_an_error_for_rails_select_map.md

@@ -0,0 +1 @@
+* [#1121](https://github.com/rubocop/rubocop-rails/issues/1121): Fix an error for `Rails/SelectMap` when using `select(:column_name).map(&:column_name)` without receiver model. ([@koic][])

lib/rubocop/cop/rails/select_map.rb

@@ -51,10 +51,13 @@ def find_select_node(node, column_name)
           end
         end
 
+        # rubocop:disable Metrics/AbcSize
         def autocorrect(corrector, select_node, node, preferred_method)
-          corrector.remove(select_node.loc.dot.begin.join(select_node.source_range.end))
+          corrector.remove(select_node.loc.dot || node.loc.dot)
+          corrector.remove(select_node.loc.selector.begin.join(select_node.source_range.end))
           corrector.replace(node.loc.selector.begin.join(node.source_range.end), preferred_method)
         end
+        # rubocop:enable Metrics/AbcSize
 
         def match_column_name?(select_candidate, column_name)
           return false unless select_candidate.arguments.one?

spec/rubocop/cop/rails/select_map_spec.rb

@@ -45,6 +45,17 @@
     RUBY
   end
 
+  it 'registers an offense when using `select(:column_name).map(&:column_name)` without receiver model' do
+    expect_offense(<<~RUBY)
+      select(:column_name).map(&:column_name)
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `pluck(:column_name)` instead of `select` with `map`.
+    RUBY
+
+    expect_correction(<<~RUBY)
+      pluck(:column_name)
+    RUBY
+  end
+
   it 'does not register an offense when using `select(:mismatch_column_name).map(&:column_name)`' do
     expect_no_offenses(<<~RUBY)
       Model.select(:mismatch_column_name).map(&:column_name)