Non italics text treated as italics

[knzudgt]

Prerequisites

• [ x] Put an X between the brackets on this line if you have done all of the following:
  • Reproduced the problem in Safe Mode: http://flight-manual.atom.io/hacking-atom/sections/debugging/#using-safe-mode
  • Followed all applicable steps in the debugging guide: http://flight-manual.atom.io/hacking-atom/sections/debugging/
  • Checked the FAQs on the message board for common solutions: https://discuss.atom.io/c/faq
  • Checked that your issue isn't already filed: https://github.com/issues?utf8=✓&q=is%3Aissue+user%3Aatom
  • Checked that there is not already an Atom package that provides the described functionality: https://atom.io/packages

Description

language-gfm starts rendering in italics and pink colour a text following an underline, without waiting for the closing underline, not considering that the closing underline can never happen.

Steps to Reproduce

1. Open attached file and change its extension from txt to md
2. See how text is rendered in the editor following markdown rules from start to line 35
3. See what happens at line 36: the test suddenly turns pink and stays pink until the end of the document, because of the first underline in _search_form.html.erb

Expected behavior: [What you expect to happen]

language-gfm should wait for the closing underline before formatting text in italics. In markdown italics is rendered by enclosing text inside two underscores and there should be a space before and after the formatted text. An underscore does not automatically mean the user wants to write in italics. In Ruby on Rails the underscore is used as a start to name partials.

Actual behavior: [What actually happens]
language-gfm starts formatting text in italics and pink as soon as an underscore is typed. This can result in pages of wrongly formatted text.

Reproduces how often: [What percentage of the time does it reproduce?]
Always

Versions

Atom : 1.15.0
Electron: 1.3.13
Chrome : 52.0.2743.82
Node : 6.5.0

apm 1.15.3
npm 3.10.5
node 4.4.5 x64
python 2.7.6
git 2.11.0

OS: Ubuntu 14.04 LTS

Additional Information

The package Markdown preview and GitHub do not experience the same issue.
See for instance how the following line is correctly treated.

_search_form.html.erb. _search_form.html.erb. _search_form.html.erb
extract.txt