Require all API resources to inherit from a common base class

This makes changing the base class in future easier.

.rubocop.yml

@@ -335,7 +335,7 @@ Gitlab/Union:
     - 'spec/**/*'
     - 'ee/spec/**/*'
 
-API/GrapeAPIInstance:
+API/Base:
   Enabled: true
   Include:
     - 'lib/**/api/**/*.rb'

lib/api/base.rb

+# frozen_string_literal: true
+
+module API
+  class Base < Grape::API::Instance # rubocop:disable API/Base
+  end
+end

rubocop/cop/api/grape_api_instance.rb → rubocop/cop/api/base.rb

@@ -3,8 +3,8 @@
 module RuboCop
   module Cop
     module API
-      class GrapeAPIInstance < RuboCop::Cop::Cop
-        # This cop checks that APIs subclass Grape::API::Instance with Grape v1.3+.
+      class Base < RuboCop::Cop::Cop
+        # This cop checks that APIs subclass API::Base.
         #
         # @example
         #
@@ -14,19 +14,24 @@ module RuboCop
         #   end
         # end
         #
-        # # good
         # module API
         #   class Projects < Grape::API::Instance
         #   end
         # end
-        MSG = 'Inherit from Grape::API::Instance instead of Grape::API. ' \
-              'For more details check the https://gitlab.com/gitlab-org/gitlab/-/issues/215230.'
+        #
+        # # good
+        # module API
+        #   class Projects < ::API::Base
+        #   end
+        # end
+        MSG = 'Inherit from ::API::Base instead of Grape::API::Instance or Grape::API. ' \
+              'For more details check https://gitlab.com/gitlab-org/gitlab/-/issues/215230.'
 
+        def_node_matcher :grape_api, '(const (const {nil? (cbase)} :Grape) :API)'
         def_node_matcher :grape_api_definition, <<~PATTERN
           (class
             (const _ _)
-            (const
-              (const nil? :Grape) :API)
+            {#grape_api (const #grape_api :Instance)}
             ...
           )
         PATTERN
@@ -36,6 +41,12 @@ module RuboCop
             add_offense(node.children[1])
           end
         end
+
+        def autocorrect(node)
+          lambda do |corrector|
+            corrector.replace(node, '::API::Base')
+          end
+        end
       end
     end
   end

spec/rubocop/cop/api/base_spec.rb

+# frozen_string_literal: true
+
+require 'fast_spec_helper'
+require 'rubocop'
+require 'rubocop/rspec/support'
+require_relative '../../../../rubocop/cop/api/base'
+
+RSpec.describe RuboCop::Cop::API::Base, type: :rubocop do
+  include CopHelper
+
+  subject(:cop) { described_class.new }
+
+  let(:corrected) do
+    <<~CORRECTED
+      class SomeAPI < ::API::Base
+      end
+    CORRECTED
+  end
+
+  ['Grape::API', '::Grape::API', 'Grape::API::Instance', '::Grape::API::Instance'].each do |offense|
+    it "adds an offense when inheriting from #{offense}" do
+      expect_offense(<<~CODE)
+        class SomeAPI < #{offense}
+                        #{'^' * offense.length} #{described_class::MSG}
+        end
+      CODE
+
+      expect_correction(corrected)
+    end
+  end
+
+  it 'does not add an offense when inheriting from BaseAPI' do
+    expect_no_offenses(corrected)
+  end
+end

spec/rubocop/cop/api/grape_api_instance_spec.rb

-# frozen_string_literal: true
-
-require 'fast_spec_helper'
-require 'rubocop'
-require_relative '../../../../rubocop/cop/api/grape_api_instance'
-
-RSpec.describe RuboCop::Cop::API::GrapeAPIInstance do
-  include CopHelper
-
-  subject(:cop) { described_class.new }
-
-  it 'adds an offense when inheriting from Grape::API' do
-    inspect_source(<<~CODE)
-      class SomeAPI < Grape::API
-      end
-    CODE
-
-    expect(cop.offenses.size).to eq(1)
-  end
-
-  it 'does not add an offense when inheriting from Grape::API::Instance' do
-    inspect_source(<<~CODE)
-      class SomeAPI < Grape::API::Instance
-      end
-    CODE
-
-    expect(cop.offenses.size).to be_zero
-  end
-end