[Fix #9617] Disable suggested extensions when using the --stdin option

changelog/change_disable_suggested_extensions_when_using.md

@@ -0,0 +1 @@
+* [#9617](https://github.com/rubocop/rubocop/issues/9617): Disable suggested extensions when using the `--stdin` option. ([@dvandersluis][])

lib/rubocop/cli/command/suggest_extensions.rb

@@ -43,7 +43,8 @@ def skip?
           # 2. When given RuboCop options that it doesn't make sense for
           # 3. For all formatters except specified in `INCLUDED_FORMATTERS'`
           ENV['CI'] ||
-            @options[:only] || @options[:debug] || @options[:list_target_files] || @options[:out] ||
+            @options[:only] || @options[:debug] || @options[:list_target_files] ||
+            @options[:out] || @options[:stdin] ||
             !INCLUDED_FORMATTERS.include?(current_formatter)
         end
 

spec/rubocop/cli_spec.rb

@@ -2057,6 +2057,17 @@ def find_suggestions
       end
     end
 
+    context 'when given --stdin' do
+      it 'does not show the suggestion' do
+        begin
+          $stdin = StringIO.new('p $/')
+          expect { cli.run(['--stdin', 'example.rb']) }.not_to suggest_extensions
+        ensure
+          $stdin = STDIN
+        end
+      end
+    end
+
     context 'when given a non-supported formatter' do
       it 'does not show the suggestion' do
         expect { cli.run(['example.rb', '--format', 'simple']) }.not_to suggest_extensions