Accented keyboard characters requiring two keystrokes for input, add extra characters in editor, i.e. "café " => "caf´é " on Safari

When editing files directly in Gitlab on Safari, then accented characters are often used (for non-english). Then those letters appear like two character, the accent and then the letter. This applies to characters ("glyphs") that require two keystroke to enter. Exists for GitLab Community Edition 9.4.2 and previous editions (unknown start of issue).

Summary

Accented keyboard characters requiring two keystrokes for input, mishandled in editor on Safari.

Steps to reproduce

Open markdown file in any project for editing in Safari browser on Mac. Enter the letters, í, ó, ú, á or other letters that require two keystrokes to register. Note: To reproduce you may use the "Keyboard Viewer" on macOS and change the keyboard to Icelandic (or many other European languages). Then those letters may be input by pressing the accent key "'", "o" key and followed by space " " key, the output is "´ó " when it should register as: "ó " Write "café " and you get: "caf´é "

Example Project

N.a.

What is the current bug behavior?

When entering characters requiring two keystrokes, the accent keystroke is double registered. In editor (in Safari browser) pressing the accent key "'", "o" key and followed by space " " key, the output is "´ó " when it should register as: "ó " Exists for GitLab Community Edition 9.4.2

What is the expected correct behavior?

The expected behaviour is to wait for the next keystroke after accent key, thus not register the accent key as input character. In editor pressing the accent key "'", "o" key and followed by space " " key, the output should register as: "ó "

Relevant logs and/or screenshots

bug

Output of checks

This bug happens on GitLab.com

Results of GitLab environment info

Expand for output related to GitLab environment info 
(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:env:info)


(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production)

Results of GitLab application Check

Expand for output related to the GitLab application check 
(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:check SANITIZE=true)


(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true)


(we will only investigate if the tests are passing)

Possible fixes

(If you can, link to the line of code that might be responsible for the problem)

Edited by Hannes Sverrisson