I am unable to use the <Esc> key to leave insert mode and return to Normal Mode. This has 'apparently' happened without any known change, but could be related to a not-so-recent bump of my IntelliJ version (IntelliJIdea2019.1 -> IntelliJIdea2019.2).
One possible solution mentioned online that I tried was to disable, then re-enable ideaVim in Menu | Tools | Vim emulation. Trying this did not appear to solve the problem.
Comparing my working vim_settings.xml file and broken vim_settings.xml file (~/Library/Preferences/IntelliJIdea2019.1/options/vim_settings.xml), I noticed the following element:
<application>
<component name="VimSettings">
<state version="4" enabled="false" />
I noticed that when running:
watch "head ~/Library/Preferences/IntelliJIdea2019.1/options/vim_settings.xml"
This file did not update. This was not something I would of expected, so I updated the file manually.
The manually change to this file, changing enabled="false" to enabled="true", fixed this issue for me.
I think this could be a bug related to IdeaVim, but it could even be IntelliJ and happening elsewhere?