Rails 6 Zeitwerk Mode for Dependencies Autoloading breaks external Agents

[alessio-signorini]

External agents which rely on huginn_agent are loaded during initialization and injected in Agent::TYPES.

Rails 6 implements a new dependencies autoloading system called Zeitwerk Mode.

Unfortunately this change breaks huginn_agent paradigm because Agent::TYPES will be rebuild from scratch after initialization and only contain default agents.

It also generates a lengthy warning when running tests

DEPRECATION WARNING: Initialization autoloaded the constants AssignableTypes,
MarkdownClassAttributes, JsonSerializedField, RdbmsFunctions, WorkingHelpers,
LiquidInterpolatable, HasGuid, LiquidDroppable, DryRunnable, SortableEvents,
OwnedByValidator, Agent, and FormConfigurable.

Being able to do this is deprecated. Autoloading during initialization is going
to be an error condition in future versions of Rails.

Reloading does not reboot the application, and therefore code executed during
initialization does not run again. So, if you reload AssignableTypes, for example,
the expected changes won't be reflected in that stale Module object.

These autoloaded constants have been unloaded.

Please, check the "Autoloading and Reloading Constants" guide for solutions.
 (called from <top (required)> at /home/alessio/huginn/config/environment.rb:5)

[alessio-signorini]

Current workaround is to opt-out of Zeitwerk Mode adding

config.autoloader = :classic

to config/application.rb but a more permanent fix needs to be implemented.

[dsander]

Hmm this is odd I am using a bunch of Agent gems in production and don't seem to have any issues with it. In which environments are you seeing the issue?

[alessio-signorini]

I too have a production system that kept/keeps chugging along and drove me nuts when suddenly (upgrade to Rails 6) I could no longer develop locally external gems!

I just looked at your commits and on May 26th you did force config.autoloader to classic.

[dsander]

Urg, that is annoying I thought I still had Agent gems active in my development environment. I guess the auto-reloader changed in some way that it breaks.I think we should still try to support the new autoloader because I am assuming Rails will get rid of the old one at some point, but I don't know when I have the time to work on it.

[alessio-signorini]

@dsander - now that huginn_agent is part of the master codebase, we could improve/expand the definition of TYPES to include Agent gems and easily/cleanly solve this. I can take a stab at it if it sounds good to you.

[dsander]

Sure, that would be great!

[alessio-signorini]

Patch is ready and quite simple (example below). As soon the change in huginn_agent is merged (will make things cleaner) I'll open a PR for this.

    def types
      all_agents.map(&:constantize)
    end

    def all_agents
      const_get(:TYPES) + HuginnAgent.additional_agents
    end

    def valid_type?(type)
      all_agents.include?(type)
    end

[dsander]

That's great! Can you open a PR to Huginn as well? You can switch the branch of huginn_agent in the Gemfile similar to this