Extend PreventIndexCreation cop

This commit extends our existing cop to catch false positives
when the table_name is a string or a constant.

rubocop/cop/migration/prevent_index_creation.rb

@@ -12,16 +12,29 @@ class PreventIndexCreation < RuboCop::Cop::Cop
 
         MSG = "Adding new index to #{FORBIDDEN_TABLES.join(", ")} is forbidden, see https://gitlab.com/gitlab-org/gitlab/-/issues/332886"
 
+        def on_new_investigation
+          super
+          @forbidden_tables_used = false
+        end
+
         def_node_matcher :add_index?, <<~PATTERN
-          (send nil? :add_index (sym #forbidden_tables?) ...)
+          (send nil? :add_index ({sym|str} #forbidden_tables?) ...)
         PATTERN
 
         def_node_matcher :add_concurrent_index?, <<~PATTERN
-          (send nil? :add_concurrent_index (sym #forbidden_tables?) ...)
+          (send nil? :add_concurrent_index ({sym|str} #forbidden_tables?) ...)
         PATTERN
 
-        def forbidden_tables?(node)
-          FORBIDDEN_TABLES.include?(node)
+        def_node_matcher :forbidden_constant_defined?, <<~PATTERN
+          (casgn nil? _ ({sym|str} #forbidden_tables?))
+        PATTERN
+
+        def_node_matcher :add_concurrent_index_with_constant?, <<~PATTERN
+          (send nil? :add_concurrent_index (const nil? _) ...)
+        PATTERN
+
+        def on_casgn(node)
+          @forbidden_tables_used = !!forbidden_constant_defined?(node)
         end
 
         def on_def(node)
@@ -32,8 +45,18 @@ def on_def(node)
           end
         end
 
+        private
+
+        def forbidden_tables?(node)
+          FORBIDDEN_TABLES.include?(node.to_sym)
+        end
+
         def offense?(node)
-          add_index?(node) || add_concurrent_index?(node)
+          add_index?(node) || add_concurrent_index?(node) || any_constant_used_with_forbidden_tables?(node)
+        end
+
+        def any_constant_used_with_forbidden_tables?(node)
+          add_concurrent_index_with_constant?(node) && @forbidden_tables_used
         end
       end
     end

spec/rubocop/cop/migration/prevent_index_creation_spec.rb

@@ -15,22 +15,63 @@
     end
 
     context 'when adding an index to a forbidden table' do
-      it "registers an offense when add_index is used", :aggregate_failures do
-        forbidden_tables.each do |table|
-          expect_offense(<<~RUBY)
-            def change
-              add_index :#{table}, :protected
-              ^^^^^^^^^ Adding new index to #{forbidden_tables_list} is forbidden, see https://gitlab.com/gitlab-org/gitlab/-/issues/332886
-            end
-          RUBY
+      context 'when table_name is a symbol' do
+        it "registers an offense when add_index is used", :aggregate_failures do
+          forbidden_tables.each do |table_name|
+            expect_offense(<<~RUBY)
+              def change
+                add_index :#{table_name}, :protected
+                ^^^^^^^^^ Adding new index to #{forbidden_tables_list} is forbidden, see https://gitlab.com/gitlab-org/gitlab/-/issues/332886
+              end
+            RUBY
+          end
+        end
+
+        it "registers an offense when add_concurrent_index is used", :aggregate_failures do
+          forbidden_tables.each do |table_name|
+            expect_offense(<<~RUBY)
+              def change
+                add_concurrent_index :#{table_name}, :protected
+                ^^^^^^^^^^^^^^^^^^^^ Adding new index to #{forbidden_tables_list} is forbidden, see https://gitlab.com/gitlab-org/gitlab/-/issues/332886
+              end
+            RUBY
+          end
         end
       end
 
-      it "registers an offense when add_concurrent_index is used", :aggregate_failures do
-        forbidden_tables.each do |table|
+      context 'when table_name is a string' do
+        it "registers an offense when add_index is used", :aggregate_failures do
+          forbidden_tables.each do |table_name|
+            expect_offense(<<~RUBY)
+              def change
+                add_index "#{table_name}", :protected
+                ^^^^^^^^^ Adding new index to #{forbidden_tables_list} is forbidden, see https://gitlab.com/gitlab-org/gitlab/-/issues/332886
+              end
+            RUBY
+          end
+        end
+
+        it "registers an offense when add_concurrent_index is used", :aggregate_failures do
+          forbidden_tables.each do |table_name|
+            expect_offense(<<~RUBY)
+              def change
+                add_concurrent_index "#{table_name}", :protected
+                ^^^^^^^^^^^^^^^^^^^^ Adding new index to #{forbidden_tables_list} is forbidden, see https://gitlab.com/gitlab-org/gitlab/-/issues/332886
+              end
+            RUBY
+          end
+        end
+      end
+
+      context 'when table_name is a constant' do
+        it "registers an offense when add_concurrent_index is used", :aggregate_failures do
           expect_offense(<<~RUBY)
+            INDEX_NAME = "index_name"
+            TABLE_NAME = :ci_builds
+            disable_ddl_transaction!
+
             def change
-              add_concurrent_index :#{table}, :protected
+              add_concurrent_index TABLE_NAME, :protected
               ^^^^^^^^^^^^^^^^^^^^ Adding new index to #{forbidden_tables_list} is forbidden, see https://gitlab.com/gitlab-org/gitlab/-/issues/332886
             end
           RUBY
@@ -46,6 +87,20 @@ def change
           end
         RUBY
       end
+
+      context 'when using a constant' do
+        it 'does not register an offense' do
+          expect_no_offenses(<<~RUBY)
+            disable_ddl_transaction!
+
+            TABLE_NAME = "not_forbidden"
+
+            def up
+              add_concurrent_index TABLE_NAME, :protected
+            end
+          RUBY
+        end
+      end
     end
   end