Rails Rake task to dump the current environment's database into fixture files.

lib-tasks-db_fixtures_dump.rake

namespace :db do
  namespace :fixtures do
    desc "Dumps the current environment's database into fixtures (uses FIXTURES_PATH)"
    task dump: :environment do
      Rails.application.eager_load!

      models = ApplicationRecord.descendants.reject { |model| model.primary_key.nil? }

      fixture_files = ENV["FIXTURES"].to_s.split(",")
      if fixture_files.any?
        models = models.select { |model| fixture_files.include? model.name.pluralize.underscore }
      end
      
      models.each do |model|
        fixture_scope = model.all.order(model.primary_key)
        next if fixture_scope.none?

        fixture_dir = ENV["FIXTURES_PATH"] || "test/fixtures"
        fixture_file = Rails.root.join fixture_dir, "#{model.name.pluralize.underscore}.yml"

        fixture_data = fixture_scope.map do |record|
          [
            "#{model.name.demodulize.underscore}_#{record[model.primary_key]}",
            record.attributes.as_json.slice(*model.column_names)
          ]
        end
        fixture_yaml = Hash[fixture_data].to_yaml.gsub(/\A---\n/, "")

        FileUtils.mkdir_p File.dirname fixture_file
        File.write fixture_file, fixture_yaml
      end
    end
  end
end