Rails (test-)helper to circumvent W3C validation errors for button_to

may_ignore_autocomplete_errors_for_hidden.rb

# coding: utf-8
ENV['RAILS_ENV'] ||= 'test'
require_relative '../config/environment'
require 'rails/test_help'
require 'w3c_validators'  # Key module. Write in Gemfile:  gem 'w3c_validators'

# meant to be included in /test/test_helper.rb
class ActiveSupport::TestCase

  # Botch fix of W3C validation errors for HTMLs generated by button_to
  #
  # On 2022-10-26, W3C validation implemented a check, which may raise an error:
  #
  # > An input element with a type attribute whose value is hidden must not have an autocomplete attribute whose value is on or off.
  #
  # This is particularly the case for HTMLs generated by button_to as of Rails 7.0.4.
  # It seems the implementation in Rails was deliberate to deal with mal-behaviours of
  # Firefox (Github Issue-42610: https://github.com/rails/rails/issues/42610 ).
  #
  # Whatever the reason is, it is highly inconvenient for developers who
  # use W3C validation for their Rails apps.
  # 
  # This routine takes a W3C-validation error object (Array) and
  # return the same Array where the specific errors are deleted
  # so that one could still test the other potential errors with the W3C validation.
  # The said errors are recorded with +logger.warn+ (if +prefix+ is given).
  #   
  # Note that this routine does nothing *unless* the config parameter
  #   config.ignore_w3c_validate_hidden_autocomplete = true
  # is set in config, e.g., in the file (if for testing use only):
  #   /config/environments/test.rb
  #
  # == References
  #
  # * Stackoverflow: https://stackoverflow.com/questions/74256523/rails-button-to-fails-with-w3c-validator
  # * Github: https://github.com/validator/validator/pull/1458
  # * HTML Spec: https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#autofilling-form-controls:-the-autocomplete-attribute:autofill-anchor-mantle-2
  #
  # @example Usage, maybe in /test/test_helper.rb
  #   # Make sure to write in /config/environments/test.rb
  #   #    config.ignore_w3c_validate_hidden_autocomplete = true
  #   #
  #   #require 'w3c_validators'
  #   bind = caller_locations(1,1)[0]  # Ruby 2.0+
  #   caller_info = sprintf "%s:%d", bind.absolute_path.sub(%r@.*(/test/)@, '\1'), bind.lineno
  #   errors = @validator.validate_text(response.body).errors
  #   prefix = "Ignores W3C validation errors (#{caller_info}): "
  #   errors = _may_ignore_autocomplete_errors_for_hidden(errors, prefix)
  #   assert_empty errors, "Failed in W3C validation: "+errors.map(&:to_s).inspect
  #
  # @param errs [Array<W3CValidators::Message>] Output of [email protected]_text(response.body).errors+
  # @param prefix [String] Prefix of the warning message recorded with Logger.
  #    If empty, no message is recorded in Logger.
  # @return [Array<String, W3CValidators::Message>]
  def _may_ignore_autocomplete_errors_for_hidden(errs, prefix="")
    removeds = []
    return errs if !Rails.configuration.ignore_w3c_validate_hidden_autocomplete
    errs.map{ |es|
      # Example of an Error:
      #   ERROR; line 165: An “input” element with a “type” attribute whose value is “hidden” must not have an “autocomplete” attribute whose value is “on” or “off”
      if /\AERROR\b.+\binput\b[^a-z]+\belement.+\btype\b.+\bhidden\b.+\bautocomplete\b[^a-z]+\battribute\b/i =~ es.to_s
        removeds << es
        nil
      else
        es
      end
    }.compact

  ensure
    # Records it in Logger
    if !removeds.empty? && !prefix.blank?
      Rails.logger.warn(prefix + removeds.map(&:to_s).uniq.inspect)
    end
  end
end