Don't force ActionMailer to lazy load before configuration.

[Benjamin-Dobell]

Closes #86

[Benjamin-Dobell]

This has failed CI on 2.2.10 and 2.3.7, but passed on the other 3 ruby versions (older and newer). This appears to be an issue with the CI/project setup and is unrelated to this PR:

Could not find gem 'bundler (~> 1.16.2)' in any of the relevant sources:

[cgunther]

As a result of upgrading from Rails 5.2 to 6.0, I'm hitting a similar problem as #86 and I believe this fix is in the right direction, but not perfect yet.

Rails 6.0 deprecates the old jobs used to send emails in the background in favor of a new job (ActionMailer::MailDeliveryJob). The new_framework_defaults_6_0.rb initializer file has a line for you to uncomment to opt into the new job once you're stable on 6.0, however uncommenting it doesn't have the intended effect of using the new job.

The issue is that the initializer file sets the new job via Rails.application.config.action_mailer, and when ActionMailer::Base is loaded, the config you've set is copied to ActionMailer::Base. This gem currently eagerly loads ActionMailer::Base before configuration (and thus before initializers) as a result of adding the delivery method:

mailgun-ruby/lib/railgun/railtie.rb

Lines 5 to 7 in f0f267a

	config.before_configuration do
	ActionMailer::Base.add_delivery_method :mailgun, Railgun::Mailer
	end

That means the config is already copied from Rails.application.config.action_mailer to ActionMailer::Base before the initializer file is run to set the delivery job, thus yielding no effect.

Using ActiveSupport.on_load(:action_mailer) as this PR does is better so we don't force eagerly loading ActionMailer::Base, however I believe the initializer in this PR ends up running after the initializer defined by ActionMailer:
https://github.com/rails/rails/blob/464a86f90ba89ac97aac48e4191fffc8309c445f/actionmailer/lib/action_mailer/railtie.rb#L17

Which copies your config to ActionMailer::Base:
https://github.com/rails/rails/blob/464a86f90ba89ac97aac48e4191fffc8309c445f/actionmailer/lib/action_mailer/railtie.rb#L53

Which errors when it gets to Rails.application.config.action_mailer.mailgun_settings since there is no ActionMailer::Base.mailgun_settings= method (yet). The initializer defined in this PR would be run later, adding the delivery method, thus defining the ActionMailer::Base.mailgun_settings= method.

To fix this, I believe this gem's initializer needs to run before the one provided by ActionMailer so that we can add the delivery method before we try copying the mailgun_settings. I believe this can be achieved by changing the initializer line as follows:

initializer "railgun.configure_rails_initialization", before: 'action_mailer.set_configs' do

Separately, I'm not sure where this line is coming from, perhaps something for your own application code?

ActiveSupport.run_load_hooks(:mailgun_mailer, Railgun::Mailer)

[obahareth]

@cgunther @Benjamin-Dobell Any idea when this might be merged guys? Thanks!

[cgunther]

I'm just a fellow user of this library, so I have no control over merging. I stumbled onto the original fix and provided my feedback on how it worked for me.

[javierav]

Three hours of my life wasted until I found that the fault was in this gem! 🤯 And the problem was detected in February 2019 and still, almost two years later, it has not been fixed! 🤬 Bye bye Mailgun...

[javierav]

For future reference, the error that I was getting is:

DEPRECATION WARNING: Initialization autoloaded the constants ActionText::ContentHelper and ActionText::TagHelper.

Related with rails/rails#36546

[donrestarone]

Any updates on if this change will be merged? Its Feb 2021 and this is still an issue.

[subdigital]

The lack of response on this thread is concerning. Any updates from mailgun on when we can expect this to be resolved?

[Benjamin-Dobell]

How Not to Do Open Source 101, with your lecturer Mailgun: #227