undefined method `+' for nil:NilClass

[boris-petrov]

Capybara 3.10.0, Selenium 3.14.1 used via JRuby.

     NoMethodError:
       undefined method `+' for nil:NilClass
     # ./features/build/tmp/jrubyExec/gems/capybara-3.10.0/lib/capybara/selenium/node.rb:184:in `path'
     # ./features/build/tmp/jrubyExec/gems/capybara-3.10.0/lib/capybara/node/element.rb:442:in `inspect'
     # ./features/build/tmp/jrubyExec/gems/capybara-3.10.0/lib/capybara/queries/selector_query.rb:52:in `description'
     # ./features/build/tmp/jrubyExec/gems/capybara-3.10.0/lib/capybara/queries/selector_query.rb:57:in `applied_description'
     # ./features/build/tmp/jrubyExec/gems/capybara-3.10.0/lib/capybara/queries/selector_query.rb:115:in `failure_message'
     # ./features/build/tmp/jrubyExec/gems/capybara-3.10.0/lib/capybara/result.rb:105:in `failure_message'
     # ./features/build/tmp/jrubyExec/gems/capybara-3.10.0/lib/capybara/node/matchers.rb:104:in `block in assert_selector'
     # ./features/build/tmp/jrubyExec/gems/capybara-3.10.0/lib/capybara/node/matchers.rb:740:in `block in _verify_selector_result'
     # ./features/build/tmp/jrubyExec/gems/capybara-3.10.0/lib/capybara/node/base.rb:82:in `synchronize'
     # ./features/build/tmp/jrubyExec/gems/capybara-3.10.0/lib/capybara/node/matchers.rb:739:in `_verify_selector_result'
     # ./features/build/tmp/jrubyExec/gems/capybara-3.10.0/lib/capybara/node/matchers.rb:102:in `assert_selector'
     # ./features/build/tmp/jrubyExec/gems/capybara-3.10.0/lib/capybara/rspec/matchers.rb:67:in `element_matches?'
     # ./features/build/tmp/jrubyExec/gems/capybara-3.10.0/lib/capybara/rspec/matchers.rb:51:in `matches?'
     ...

This is very sporadic in our test suite and I'm not sure what's causing it but in any case Capybara should give an error message and not blow up with a NoMethodError. Please tell me how I can help more.

[twalpole]

What type of element is the scoping element you are searching within ?

[boris-petrov]

This is the code that causes this exception:

dropdown = find('.navbar a', text: 'Some text').find(:xpath, './following-sibling::*[1]', visible: :all)
expect(dropdown).to have_css('a', visible: :all, exact_text: name)

The second line is followed by the stacktrace that I pasted earlier.

[twalpole]

The following-sibling is creating an issue when trying to generate the path of the scoping element (because it is outside its “parent” sub tree) if no matching ‘a’ element is found. I’ll try and have a fix out later today (California time)

[twalpole]

@boris-petrov In the meantime you should be able to workaround the issue by combining the two finds so there is no scoping happening with something like

dropdown = find(:xpath, XPath.css('.nabvar a')[XPath.contains('Some text')].following_sibling[1], visible: :all)

[twalpole]

Hmmm -- this might not actually have anything to do with the sibling portion of it -- is it possible the dropdown element is going away while have_css is running? and is this all running inside a within block by any chance?

[twalpole]

I have not been able to reproduce this - but have put in a fix at the current point of failure - Please try branch issue_2120 and see if that fixes things for you.

[boris-petrov]

Thanks for the support! This code is not run in a within block, however it is possible that the dropdown is rerendered, yes. Which means that it disappears and is redrawn. We expect that in this case Capybara would just retry the have_css check. Is that wrong as an assumption? We use a single-page-application framework (Ember.js) which redraws stuff all the time and such race-conditions are ubiquitous.

P.S. I'll try your fix. But, as I said, it is sporadic so we'll see how long it takes. :)

[twalpole]

@boris-petrov Yes it should retry (if the undefined method error hadn't raised), I was just trying to narrow down how the error came about so I could generate a test case for it.

[twalpole]

I've merged this in to master branch now -- I'm going to close this issue, we can reopen if the problem shows up again.