1 files changed, 59 insertions, 0 deletions
diff --git a/rubocop/cop/migration/add_limit_to_string_columns.rb b/rubocop/cop/migration/add_limit_to_string_columns.rb
new file mode 100644
index 00000000000..30affcbb089
--- /dev/null
+++ b/rubocop/cop/migration/add_limit_to_string_columns.rb
@@ -0,0 +1,59 @@
+# frozen_string_literal: true
+
+require_relative '../../migration_helpers'
+
+module RuboCop
+  module Cop
+    module Migration
+      # Cop that enforces length constraints to string columns
+      class AddLimitToStringColumns < RuboCop::Cop::Cop
+        include MigrationHelpers
+
+        ADD_COLUMNS_METHODS = %i(add_column add_column_with_default).freeze
+
+        MSG = 'String columns should have a limit constraint. 255 is suggested'.freeze
+
+        def on_def(node)
+          return unless in_migration?(node)
+
+          node.each_descendant(:send) do |send_node|
+            next unless string_operation?(send_node)
+
+            add_offense(send_node, location: :selector) unless limit_on_string_column?(send_node)
+          end
+        end
+
+        private
+
+        def string_operation?(node)
+          modifier = node.children[0]
+          migration_method = node.children[1]
+
+          if migration_method == :string
+            modifier.type == :lvar
+          elsif ADD_COLUMNS_METHODS.include?(migration_method)
+            modifier.nil? && string_column?(node.children[4])
+          end
+        end
+
+        def string_column?(column_type)
+          column_type.type == :sym && column_type.value == :string
+        end
+
+        def limit_on_string_column?(node)
+          migration_method = node.children[1]
+
+          if migration_method == :string
+            limit_present?(node.children)
+          elsif ADD_COLUMNS_METHODS.include?(migration_method)
+            limit_present?(node)
+          end
+        end
+
+        def limit_present?(statement)
+          !(statement.to_s =~ /:limit/).nil?
+        end
+      end
+    end
+  end
+end