Don't force encrypted database columns to have a text limit

rubocop/cop/migration/add_limit_to_text_columns.rb

@@ -6,6 +6,10 @@ module RuboCop
   module Cop
     module Migration
       # Cop that enforces always adding a limit on text columns
+      #
+      # Text columns starting with `encrypted_` are very likely used
+      # by `attr_encrypted` which controls the text length. Those columns
+      # should not add a text limit.
       class AddLimitToTextColumns < RuboCop::Cop::Cop
         include MigrationHelpers
 
@@ -102,6 +106,8 @@ module RuboCop
         # Check if there is an `add_text_limit` call for the provided
         # table and attribute name
         def text_limit_missing?(node, table_name, attribute_name)
+          return false if encrypted_attribute_name?(attribute_name)
+
           limit_found = false
 
           node.each_descendant(:send) do |send_node|
@@ -118,6 +124,10 @@ module RuboCop
 
           !limit_found
         end
+
+        def encrypted_attribute_name?(attribute_name)
+          attribute_name.to_s.start_with?('encrypted_')
+        end
       end
     end
   end

spec/rubocop/cop/migration/add_limit_to_text_columns_spec.rb

@@ -129,6 +129,28 @@ RSpec.describe RuboCop::Cop::Migration::AddLimitToTextColumns, type: :rubocop do
       end
     end
 
+    context 'when text columns are used for encryption' do
+      it 'registers no offenses' do
+        expect_no_offenses(<<~RUBY)
+          class TestTextLimits < ActiveRecord::Migration[6.0]
+            DOWNTIME = false
+            disable_ddl_transaction!
+
+            def up
+              create_table :test_text_limits, id: false do |t|
+                t.integer :test_id, null: false
+                t.text :encrypted_name
+              end
+
+              add_column :encrypted_test_text_limits, :encrypted_email, :text
+              add_column_with_default :encrypted_test_text_limits, :encrypted_role, :text, default: 'default'
+              change_column_type_concurrently :encrypted_test_text_limits, :encrypted_test_id, :text
+            end
+          end
+        RUBY
+      end
+    end
+
     context 'on down' do
       it 'registers no offense' do
         expect_no_offenses(<<~RUBY)