use of JavaScript's let will fail silently

[pawel2105]

I've stumbled across a bug where JavaScript enabled specs fail silently due to the use of JavaScript's let assignment operator. Using let instead of var will break whatever other code resides in the same <script> tag as the let keyword.

Capybara.javascript_driver = :poltergeist

Capybara.register_driver :poltergeist do |app|
  options = { js_errors: true }
  Capybara::Poltergeist::Driver.new(app, options)
end

This is true despite having js_errors set to be true.

To reproduce run a spec for a page that has:

<script type="text/javascript">
  var message = 'works fine';
</script>

versus one that has:

<script type="text/javascript">
  let message = 'fails silently';
</script>

[twalpole]

This is a limitation of PhantomJS. PhantomJS doesn't support ES6, and let is an ES6 feature

[twalpole]

It appears that PhantomJS only reports runtime errors, not parse time errors. Not sure there's anything we can do about that if PhantomJS doesn't tell us.

[diegoesp]

+1