Add cop to ensure reversibility of add_concurrent_index

2 files changed, 35 insertions, 0 deletions

diff --git a/rubocop/cop/migration/add_concurrent_index.rb b/rubocop/cop/migration/add_concurrent_index.rb
new file mode 100644
index 00000000000..332fb7dcbd7
--- /dev/null
+++ b/rubocop/cop/migration/add_concurrent_index.rb
@@ -0,0 +1,34 @@
+require_relative '../../migration_helpers'
+
+module RuboCop
+  module Cop
+    module Migration
+      # Cop that checks if `add_concurrent_index` is used with `up`/`down` methods
+      # and not `change`.
+      class AddConcurrentIndex < RuboCop::Cop::Cop
+        include MigrationHelpers
+
+        MSG = '`add_concurrent_index` is not reversible so you must manually define ' \
+          'the `up` and `down` methods in your migration class, using `remove_index` in `down`'.freeze
+
+        def on_send(node)
+          return unless in_migration?(node)
+
+          name = node.children[1]
+
+          return unless name == :add_concurrent_index
+
+          node.each_ancestor(:def) do |def_node|
+            next unless method_name(def_node) == :change
+
+            add_offense(def_node, :name)
+          end
+        end
+
+        def method_name(node)
+          node.children.first
+        end
+      end
+    end
+  end
+end
diff --git a/rubocop/rubocop.rb b/rubocop/rubocop.rb
index ea8e0f64b0d..a50a522cf9d 100644
--- a/rubocop/rubocop.rb
+++ b/rubocop/rubocop.rb
@@ -3,4 +3,5 @@ require_relative 'cop/gem_fetcher'
 require_relative 'cop/migration/add_column'
 require_relative 'cop/migration/add_column_with_default'
 require_relative 'cop/migration/add_concurrent_foreign_key'
+require_relative 'cop/migration/add_concurrent_index'
 require_relative 'cop/migration/add_index'