ActiveModel::Errors support

[calebuharrison]

Hello and thanks for this fantastic gem!

In my app, I've monkeypatched the provided pack_with and unpack_with methods for the ActiveRecord::Base extension to include errors by default:

class UniversalID::Extensions::ActiveRecordBasePacker
  def pack_with(packer)
    packer.write record.class.name
    packer.write packable_attributes
    error_details = record.errors.details
    packer.write error_details
  end
end

class UniversalID::Extensions::ActiveRecordBaseUnpacker
  class << self
    def unpack_with(unpacker)
      class_name = unpacker.read
      attributes = unpacker.read || {}
      instance = create_instance(class_name, attributes)
      error_details = unpacker.read

      error_details.each do |attribute, details_array|
        details_array.each do |error_details|
          error_type = error_details.delete(:error)
          instance.errors.add(attribute, error_type, **error_details)
        end
      end

      instance
    end
  end
end

This has opened up a really nice little flow in my controllers with the help of a simple utility class:

class ApplicationController < ActionController::Base
  # ...

  private

  def flash_pack
    return @flash_pack if defined?(@flash_pack)
    @flash_pack = FlashPack.new(flash)
  end

  class FlashPack
    def initialize(flash)
      @flash = flash
    end

    def []=(key, value)
      @flash[key] = URI::UID.build(value, include_changes: true).payload
    end

    def [](key)
      URI::UID.from_payload(@flash[key]).decode if @flash[key]
    end
  end
end

class PostsController < ApplicationController
  def new
    # view renders form_with model: @post, including validation errors from previous form submission (if present)
    @post = flash_pack[:post] || Post.new
  end

  def create
    post = Post.new(post_params)

    if post.save
      redirect_to another_controller_action
    else
      # pack the post into the flash
      flash_pack[:post] = post
    end
  end
end

Since the extension shipped by the gem is for ActiveRecord::Base, I think out-of-the-box support for errors would be great! I imagine this behavior could be toggled with an additional prepack option, include_errors.

Happy to write a PR if this sounds reasonable to you! Thanks again for all of your contributions to the ruby and rails ecosystems.

[hopsoft]

This is fantastic. I'd be happy to accept a PR for this. 🙌🏻