Schneiderlein

Schneiderlein is a Rack middleware to catch parse errors coming from ActionDispatch::ParamsParser. Malformed XML presents a 500 Internal Server Error to your API consumer. It's hardly meaningful, should instead be in the 4xx range and most importantly: it's not helping.

Since the error appears early in the middleware stack, there is no way to use rescue_from on controller-level in a Rails app. Schneiderlein blanks the defective POST data from the request environment, saves the ParseError's message and passes the modified Rack env along the middleware stack.

The original error message is saved as rack.schneiderlein.parse_errors in the request environment. Schneiderlein::Catch aims to provide a convenient accessor. See the usage example below.

Usage

Add the gem to your Rails app's Gemfile. In your API controller, you may want to add something like this:

class Api::BaseController < ApplicationController
  before_action :handle_parse_errors

  respond_to :json, :xml

  protected

  def handle_parse_errors
    schneiderlein = Schneiderlein::Catch.new(request)
    respond_with schneiderlein.errors, status: 422 if schneiderlein.errors.any?
  end
end

Naming

The name Schneiderlein is derived from the fairytale »Das Tapfere Schneiderlein« (»The Valiant Little Tailor«) by the Grimm Brothers. The Valiant Little Tailor catches flies, Schneiderlein catches errors. Funny, eh?

Changelog

4.0.0

• Drop support for Rails below 6.1
• Drop support for Ruby below 3.0
• Add support for Rails 7.+
• Switch from Travis CI to GitHub Actions

3.0.0

• Drop support for Rails below 5.2
• Add support for Rails 6.+

2.0.0

• Drop support for Rails below 5.0
• Add support for Rails 5.1+

1.3.1

• Call middleware by their constants (fixes deprecation warning)

1.3.0

• Use frozen_string_literal magic comment
• Remove autoload calls

1.2.0

• Supports Rails 5
• Drops support for Rails < 4.2
• Drops support for C-Ruby v2.0.x and v2.1.x

1.1.0

• compactified error message presentation

1.0.0

• Initial release