From 021b2368d968901a01da011b8bff5a165c556e10 Mon Sep 17 00:00:00 2001
From: Earlopain <14981592+Earlopain@users.noreply.github.com>
Date: Fri, 20 Sep 2024 09:27:20 +0200
Subject: [PATCH] Emit a deprecation when custom cops inherit from
 `RuboCop::Cop::Cop`

This has been long-marked as deprecated but not everyone has gotten the memo:
https://github.com/search?q=%2F%3C+RuboCop%3A%3ACop%3A%3ACop%2F+lang%3Aruby+-is%3Afork&type=code

Some methods _are_ deprecated but its perfectly possible to just not use any of them.
---
 changelog/change_deprecation_for_cop_cop_cops.md |  1 +
 lib/rubocop/cop/cop.rb                           |  8 ++++++++
 spec/rubocop/cop/cop_spec.rb                     | 10 +++++++---
 3 files changed, 16 insertions(+), 3 deletions(-)
 create mode 100644 changelog/change_deprecation_for_cop_cop_cops.md

diff --git a/changelog/change_deprecation_for_cop_cop_cops.md b/changelog/change_deprecation_for_cop_cop_cops.md
new file mode 100644
index 000000000000..1d947c358740
--- /dev/null
+++ b/changelog/change_deprecation_for_cop_cop_cops.md
@@ -0,0 +1 @@
+* [#13253](https://github.com/rubocop/rubocop/pull/13253): Emit a deprecation when custom cops inherit from `RuboCop::Cop::Cop`. ([@earlopain][])
diff --git a/lib/rubocop/cop/cop.rb b/lib/rubocop/cop/cop.rb
index 1f853603a279..dba0f636415f 100644
--- a/lib/rubocop/cop/cop.rb
+++ b/lib/rubocop/cop/cop.rb
@@ -22,6 +22,14 @@ def call(corrector)
         end
       end
 
+      def self.inherited(_subclass)
+        super
+        warn Rainbow(<<~WARNING).yellow, uplevel: 1
+          Inheriting from `RuboCop::Cop::Cop` is deprecated. Use `RuboCop::Cop::Base` instead.
+          For more information, see https://docs.rubocop.org/rubocop/v1_upgrade_notes.html.
+        WARNING
+      end
+
       def self.support_autocorrect?
         method_defined?(:autocorrect)
       end
diff --git a/spec/rubocop/cop/cop_spec.rb b/spec/rubocop/cop/cop_spec.rb
index abd4b42167fc..84b8c1522e7a 100644
--- a/spec/rubocop/cop/cop_spec.rb
+++ b/spec/rubocop/cop/cop_spec.rb
@@ -233,9 +233,13 @@
 
     context 'when cop supports autocorrection', :restore_registry do
       let(:cop_class) do
-        stub_cop_class('RuboCop::Cop::Test::StubCop', inherit: described_class) do
-          def autocorrect(node); end
-        end
+        cop_class = nil
+        expect do # rubocop:disable RSpec/ExpectInLet
+          cop_class = stub_cop_class('RuboCop::Cop::Test::StubCop', inherit: described_class) do
+            def autocorrect(node); end
+          end
+        end.to output(/Inheriting from `RuboCop::Cop::Cop` is deprecated/).to_stderr
+        cop_class
       end
 
       context 'when offense was corrected' do