Require a :limit option for MySQL text columns created in Rails 3 app so don't unintentionally make 64K column that silently truncates.

require_limit_for_mysql_text.rb

# == config/initializers/require_limit_for_mysql_text.rb ==

# Fail when an attempt is made to specify a MySQL text
# columnn in a migration without providing a :limit value.
# This helps to prevent accidentally defining a 64K column
# (default) when a 16MB or 4GB coumn is desired.
# Note that MySQL silently truncates the data when it is
# too long for the column, so problems are only apparent
# later when attempting to retrieve the data (if then).

# Fail if class not already defined or auto-requirable.
ActiveRecord::ConnectionAdapters::AbstractMysqlAdapter

module ActiveRecord
  module ConnectionAdapters

    AbstractMysqlAdapter.class_eval do

      def type_to_sql_with_text_limit_required(type, limit = nil, precision = nil, scale = nil)
        if "#{type}" == 'text' && limit.nil?
          raise "Don't define a text column without specifying a limit."
        end
        type_to_sql_without_text_limit_required(type, limit, precision, scale)
      end

      alias_method_chain :type_to_sql, :text_limit_required

    end

  end
end