subject prefix issue

[sharmaansh21]

  def test_subject_prefix_in_test
    interceptor = ::MailInterceptor::Interceptor.new forward_emails_to: 'test@example.com',
                                                       subject_prefix: 'wheel'
    @message.subject = 'Forgot password'

    interceptor.delivering_email @message
    assert_equal "[wheel TEST] Forgot password", @message.subject

    @message.subject = 'Forgot password'
    interceptor.delivering_email @message
    assert_equal "[wheel TEST] Forgot password", @message.subject
  end

this scenario fails

-"[wheel TEST] Forgot password"
+"[[wheel TEST] TEST] Forgot password"

we need to move add_env_info_to_subject_prefix from https://github.com/bigbinary/mail_interceptor/blob/master/lib/mail_interceptor.rb#L18
to
https://github.com/bigbinary/mail_interceptor/blob/master/lib/mail_interceptor.rb#L13

@neerajdotname

[vipulnsward]

When/why would this happen?
Where would users manually rewrite email subject?

[prathamesh-sonpatki]

This will happen because the same instance of mail_interceptor object will be used for sending all the mails. So when the first mail is sent value of subject_prefix becomes [MAB TEST].

While sending next email, as same object is again used and we have following logic for subject_prefix

def add_env_info_to_subject_prefix
... 
  _prefix = production? ? subject_prefix : "#{subject_prefix} #{env.upcase}"
  self.subject_prefix = "[#{_prefix}]"
...

It will evaluate as

_prefix = "[MAB TEST] TEST"
self.subject_prefix = "[[MAB TEST] TEST]

So when we run rake test:all we see this behavior because it sends multiple emails using same object of mail_interceptor because of the way we have setup the interceptor -

interceptor = MailInterceptor::Interceptor.new(options)
ActionMailer::Base.register_interceptor(interceptor)

[vipulnsward]

I think we should not mutate subject prefix in add_env_info_to_subject_prefix.
Can you change it to just return ENV prefix if needed. It can then be directly used like-

def add_subject_prefix message
  return if subject_prefix.blank?
  message.subject = "[#{env_for_subject_prefix} #{subject_prefix}] #{message.subject}"
end