Address NameError on triple nested sub_test_case under ActionView::TestCase on Rails 6.1

[amatsuda]

Since Rails 6.1 (Zeitwerk), all ActionView::TestCase class is expected to abide by normal Ruby module naming, but this is not always the case with sub_test_case since sub_test_case generates an anonymous class with the given string as its name.

Attached is a simple reproduction of the situation, and a monkey-patch for ActionView::TestCase's sub_test_case to ignore NameError from default_helper_module!.
It is less likely that this patch introduces any new unexpected bug because that's basically how things were working with older versions of Rails with test-unit.

Please note that this patch depends on test-unit#207. We need a patched version of test-unit to be bundled to this repo in order for this patch to run (and so I expect that that test I added here would raise errors on the CI for this PR).

[kou]

Thanks.

It seems that we can avoid the default_helper_module! call by defining a custom anonymous? method:

https://github.com/rails/rails/blob/v6.1.4.4/actionpack/lib/abstract_controller/helpers.rb#L51

    def sub_test_case_class(*)
      klass = super
      class << klass
        define_method :anonymous? do
          true
        end
      end
      klass
    end

Which approach is better from a Rails developer view?

(I'm OK with both this pull request approach and the anonymous? approach.)

[amatsuda]

It seems that we can avoid the default_helper_module! call by defining a custom anonymous? method:

Thank you for the suggestion!
I knew this but at first I chose not to change the behavior of anonymous? because I felt that claiming something with a name as an anonymous object is simply a falsely claim, and so it may cause some unexpected side effect.
But I changed my mind after some more investigation after seeing your comment, because this Module#anonymous? definition is actually not in use anywhere else than this part.

Now that I pushed the change and seeing that all tests are passing, could you review this again?

[kou]

Thanks for considering these approaches.
I've merged and released a new version.

[amatsuda]

@kou Thank you very much for the quick merge and release!