Can't deliver email until CustomMailer.templates is called

[graudeejs]

Hello!

I'm trying to add hanami-mailer to my project, however I seem to have found a bug.
When I try to deliver email I get an exception
App::Mail::Mailers::Foo::Bar.deliver

NoMethodError: undefined method `fetch' for nil:NilClass
from /home/graudeejs/.asdf/installs/ruby/2.6.3/lib/ruby/gems/2.6.0/gems/hanami-mailer-1.3.1/lib/hanami/mailer/dsl.rb:85:in `templates'

However if I call .templates before .deliver it works

App::Mail::Mailers::Foo::Bar.templates
App::Mail::Mailers::Foo::Bar.deliver

I've created a small repo where this issue can be replicated:
https://github.com/graudeejs/hanami-mailer-issue-79

$ ./bin/console
[1] pry(main)> App::Mail::Mailers::Foo::Bar.deliver
NoMethodError: undefined method `fetch' for nil:NilClass
from /home/graudeejs/.asdf/installs/ruby/2.6.3/lib/ruby/gems/2.6.0/gems/hanami-mailer-1.3.1/lib/hanami/mailer/dsl.rb:85:in `templates'
[2] pry(main)> 

[mereghost]

Hi @graudeejs, thanks for your bug report and the time spent to create a sample project.

What I could find there are 2 issues in there:

1. The mailers need to be loaded before the call to Hanami::Mailer.load!.
2. Zeitwerk (maybe)

hanami-mailer 1.x series keeps references to the included classes by subverting the included hook. So when load! is called a call to templates with no args is sent. The thing is this call is triggered on all classes that Hanami::Mailer was included (which in your example would be none as they would be loaded after).

I'm not sure that you can make Zeitwerk actually load the classes beforehand.

That being said, this all is changing on hanami-mailer 2.0, that you can check on the unstable branch

[graudeejs]

1. explains it.

I've since created my own simple mail abstraction.