1 files changed, 52 insertions, 0 deletions
diff --git a/rubocop/cop/migration/prevent_strings.rb b/rubocop/cop/migration/prevent_strings.rb
new file mode 100644
index 00000000000..25c00194698
--- /dev/null
+++ b/rubocop/cop/migration/prevent_strings.rb
@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+
+require_relative '../../migration_helpers'
+
+module RuboCop
+  module Cop
+    module Migration
+      # Cop that enforces using text instead of the string data type
+      class PreventStrings < RuboCop::Cop::Cop
+        include MigrationHelpers
+
+        MSG = 'Do not use the `string` data type, use `text` instead. ' \
+          'Updating limits on strings requires downtime. This can be avoided ' \
+          'by using `text` and adding a limit with `add_text_limit`'.freeze
+
+        def_node_matcher :reverting?, <<~PATTERN
+          (def :down ...)
+        PATTERN
+
+        def on_def(node)
+          return unless in_migration?(node)
+
+          # Don't enforce the rule when on down to keep consistency with existing schema
+          return if reverting?(node)
+
+          node.each_descendant(:send) do |send_node|
+            next unless string_operation?(send_node)
+
+            add_offense(send_node, location: :selector)
+          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_COLUMN_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
+      end
+    end
+  end
+end