[Fix #12162] Fix an error for Bundler/DuplicatedGroup

Fixes #12162.

This PR fixes an error for `Bundler/DuplicatedGroup` when
there's a duplicate set of groups and the `group` value contains a splat.

changelog/fix_an_error_for_bundler_duplicated_group.md

@@ -0,0 +1 @@
+* [#12162](https://github.com/rubocop/rubocop/issues/12162): Fix an error for `Bundler/DuplicatedGroup` when there's a duplicate set of groups and the `group` value contains a splat. ([@koic][])

lib/rubocop/cop/bundler/duplicated_group.rb

@@ -117,7 +117,7 @@ def group_attributes(node)
             if argument.hash_type?
               argument.pairs.map(&:source).sort.join(', ')
             else
-              argument.value.to_s
+              argument.respond_to?(:value) ? argument.value.to_s : argument.source
             end
           end
         end

spec/rubocop/cop/bundler/duplicated_group_spec.rb

@@ -149,6 +149,21 @@
       end
     end
 
+    context 'and a set of groups is duplicated and `group` value is a splat value' do
+      it 'registers an offense' do
+        expect_offense(<<~RUBY, 'Gemfile')
+          group(*LIVE_ENVS) do
+            gem 'admin_ui'
+          end
+
+          group(*LIVE_ENVS) do
+          ^^^^^^^^^^^^^^^^^ Gem group `*LIVE_ENVS` already defined on line 1 of the Gemfile.
+            gem 'public_ui'
+          end
+        RUBY
+      end
+    end
+
     context 'and a set of groups is duplicated but `source` URLs are different' do
       it 'does not register an offense' do
         expect_no_offenses(<<~RUBY, 'Gemfile')