Split::EncapsulatedHelper can't be used in mailer views

[afn]

We have the following mailer helper:

class MyMailerHelper
  include Split::EncapsulatedHelper
  def test_enabled?
    ab_test('my_test', 'disabled', 'enabled') == 'enabled'
  end
end

and we call test_enabled? from a mailer view. This ends up raising an error:

     ActionView::Template::Error:
       undefined method `params' for #<MyMailer:0x007ff87555bd18>

The problem is this line in Split::EncapsulatedHelper:

      _params = defined?(params) ? params : {}

Due to a Rails bug (rails/rails#15613), defined?(params) returns true even though the method is not defined. The view delegates params, along with other methods, to the controller (and in this case, the "controller" is a mailer, which doesn't define that method).

I think Rails is the right place to fix the bug, but it would probably still be worthwhile to work around the issue in Split. A couple of options for this:

1. Put a begin/rescue around the call to params.
2. Don't call params at all; if there's a params method defined, then you're probably in a controller anyway, so you could just use Split::Helper.

Thoughts?

Thanks!
Tony

[andrew]

@afn If we can avoid calling params at all that would be better I think, would you like to put a pull request together for that?