Make error message clearer when the namespace is incorrect

changelog/change_error_message_on_incorrect_namespace.md

@@ -0,0 +1 @@
+* [#12641](https://github.com/rubocop/rubocop/pull/12641): Make error message clearer when the namespace is incorrect. ([@maruth-stripe][])

lib/rubocop/cop/registry.rb

@@ -300,7 +300,7 @@ def resolve_badge(given_badge, real_badge, source_path)
         unless given_badge.match?(real_badge)
           path = PathUtil.smart_path(source_path)
           warn "#{path}: #{given_badge} has the wrong namespace - " \
-               "should be #{real_badge.department}"
+               "replace it with #{given_badge.with_department(real_badge.department)}"
         end
 
         real_badge.to_s

spec/rubocop/cli_spec.rb

@@ -469,7 +469,7 @@ def and_with_args
       expect(cli.run(['--format', 'emacs', 'example.rb'])).to eq(1)
       expect($stderr.string)
         .to eq(['example.rb: Style/LineLength has the wrong ' \
-                'namespace - should be Layout',
+                'namespace - replace it with Layout/LineLength',
                 ''].join("\n"))
       # 2 real cops were disabled, and 1 that was incorrect
       # 2 real cops was enabled, but only 1 had been disabled correctly

spec/rubocop/config_loader_spec.rb

@@ -854,7 +854,7 @@ def enabled?(cop)
             .to output(
               a_string_including(
                 '.rubocop.yml: Custom/Loop has the ' \
-                "wrong namespace - should be Lint\n"
+                "wrong namespace - replace it with Lint/Loop\n"
               )
             ).to_stderr
         end

spec/rubocop/cop/registry_spec.rb

@@ -114,7 +114,7 @@
 
     it 'emits a warning when namespace is incorrect' do
       warning = '/app/.rubocop.yml: Style/MethodLength has the wrong ' \
-                "namespace - should be Metrics\n"
+                "namespace - replace it with Metrics/MethodLength\n"
       qualified = nil
 
       expect do