Merge branch 'es6-es5-poltergeist' into 'master'

Document Capybara errors from es6 in es5 file. ## What does this MR do? Documents an error that I've banged my head against twice now. ## Are there points in the code the reviewer needs to double check? ## Why was this MR needed? The greater good. ## Screenshots (if relevant) ## Does this MR meet the acceptance criteria? - [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added - [x] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md) - [ ] API support added - Tests - [ ] Added for this feature/bug - [ ] All builds are passing - [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html) - [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides) - [ ] Branch has no merge conflicts with `master` (if it does - rebase it please) - [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits) ## What are the relevant issue numbers? See merge request !6836

Merge branch 'es6-es5-poltergeist' into 'master'
21e3712a · Fatih Acet · cf47c041 · abfb4f6e · 21e3712a
Commit 21e3712a authored Oct 12, 2016 by Fatih Acet
Hide whitespace changes
Inline Side-by-side

Showing with 11 additions and 0 deletions

frontend.md doc/development/frontend.md +11 -0

No files found.
--- a/doc/development/frontend.md
+++ b/doc/development/frontend.md
@@ -223,3 +223,14 @@ For our currently-supported browsers, see our [requirements][requirements].
 [xss]: https://en.wikipedia.org/wiki/Cross-site_scripting
 [scss-style-guide]: scss_styleguide.md
 [requirements]: ../install/requirements.md#supported-web-browsers
+
+## Common Errors
+
+### Rspec (Capybara/Poltergeist) chokes on general JavaScript errors
+
+If you see very generic JavaScript errors (e.g. `jQuery is undefined`) being thrown in tests, but
+can't reproduce them manually, you may have included `ES6`-style JavaScript in files that don't
+have the `.js.es6` file extension. Either use ES5-friendly JavaScript or rename the file you're
+working in (`git mv <file>.js> <file.js.es6>`).
+
+