Deprecate poltergeist and webkit driver registration. Add cuprite.

[YusukeIwaki]

Summary

Poltergeist and capybara-webkit are already not maintained.

• https://github.com/teampoltergeist/poltergeist
• https://github.com/thoughtbot/capybara-webkit

I just happend to find the usages of them here: https://github.com/rails/rails/blob/main/actionpack/lib/action_dispatch/system_testing/driver.rb

Most users actually use Selenium with Headless Chrome in these years, and it is not encouraged to use poltergeist or capybara-webkit at this moment.

Cuprite is a good alternative driver to Poltergeist: https://evilmartians.com/chronicles/system-of-a-test-setting-up-end-to-end-rails-testing
Some guide descriptions of Poltergeist would be better to replace into Cuprite.

Other Information

[guilleiguaran]

I think we should deprecate capybara-webkit and poltergeist in 7.0 before removing them on 7.1 since some users might still depending on them.

We can add Cuprite and make it the default/recommended meanwhile.

[YusukeIwaki]

@guilleiguaran Thank you for your kind advise.:)

we should deprecate capybara-webkit and poltergeist in 7.0 before removing them on 7.1 since some users might still depending on them.

I see. This is really a breaking change. I will change the codes to show deperecation warning, instead of deleting them.

I also found a problem in adding cuprite. Some users already configure Capybara driver with the name :cuprite, and when we add cuprite into Rails, the existing configuration is not respected.
#42511 will resolve the problem.
We can add cuprite only after the PR is merged.

[guilleiguaran]

@YusukeIwaki thanks for updating this

can you check the CI failures?

[YusukeIwaki]

@guilleiguaran Hi, sorry for my mistake, I fixed the problem and rebased.

[Fjan]

I realise the writing has been on the wall for capybara-webkit some time now, but just to point out we still happily use capybara-webkit every day, simply because it runs system tests about 3 to 4 times faster than headless Chrome.

It's a bit painful to install the required old Qt version on Big Sur, but the difference between a 2 minute test suite or a 7 minute one is a considerable quality of life difference for development. Headless Chrome has steadily improved functionality, but I don't think anyone is working on closing that >300% performance gap. I realise everyone uses a CI server nowadays, but faster tests make it much easier for programmers to practice good testing hygiene.

[YusukeIwaki]

Hi @Fjan, thank you for your feedback.

capybara-webkit users can still use it even after Rails remove :webkit parameter from SystemTesting::Driver, by just registering capybara-webkit driver manually like this.

Capybara::WebKit::Driver.new(app, .......)

And the main purpose of this Pull request is dropping official support for deprecated Capybara drivers.
I completely agree to the opinion that faster testing brings better quality of life, and Cuprite is actually faster than Selenium+HeadlessChrome. Cuprite would be a good alternative to capybara-webkit if it performs well. (I didn't know the performance of capybara-webkit, sorry.)