in misc

Incompatibility rails 5.2 and mail gem: ArgumentError (:arguments expected to be an Array of individual string args)

After an innocent gem security update, suddenly my application didn't mail anymore. :S
The following crash happend when the rails application tried to send an e-mail.

Error performing ActionMailer::DeliveryJob (Job ID: xxx) from Async(mailers) in 17.17ms: ArgumentError (:arguments expected to be an Array of individual string args):
gems/mail-2.8.0/lib/mail/network/delivery_methods/sendmail.rb:53:in `initialize'
gems/mail-2.8.0/lib/mail/message.rb:278:in `new'
gems/mail-2.8.0/lib/mail/message.rb:278:in `delivery_method'
gems/actionmailer- `wrap_delivery_behavior'
gems/actionmailer- `wrap_delivery_behavior!'
gems/actionmailer- `mail'

After digging deeper in the exception trace and git diff, I figured out the mail gem was upgraded from 2.7.1 to 2.8.0.

The sendmail default sendmail arguments configuration value given by actionmailer is "-i". Which was fine for the older mail gem.

The new gem requires this to be an list of strings.
You can downgrade this OR use the following workaround in your environment file (config/environments/production.rb)

 config.action_mailer.sendmail_settings = {
   location:  "/usr/sbin/sendmail", arguments: ["-i"] 

Btw: It's a known issue and probably resolved in the next 2.8.1 release (