Every attribute on a model with 'presence: true' shouldn't allow nulls on db. This script helps identify missing not null constraints. It looks for attributes with presence: true and checks these have NOT NULL on db/structure.sql

db_nulls_check.rb

# frozen_string_literal: true

require "active_support/all"

def null_on_db?(table_name, col_name)
  db_structure = File.read("db/structure.sql")
  db_structure.match(/CREATE TABLE public.#{table_name} \((?<cols>.*?)\)/m) || {cols: ""} => { cols: attrs }
  attrs.match?(/#{col_name}.*NOT NULL/)
end

Dir.glob("app/models/*.rb").each do |file|
  File.read(file).match(/validates (?<attr>:.*),.*presence: true/) || {attr: nil} => {attr:}
  next unless attr

  table_name = File.basename(file, ".rb").pluralize
  cols = attr.delete(":").split(",").map(&:strip)
  cols&.each do |col|
    puts "#{table_name}.#{col} has presence: true but db allows null" unless null_on_db?(table_name, col)
  end
end

It looks like it may return a false positive in case you have a conditional validation, like

validates :asset_class, presence: true, if: :lease_accounting_enabled?