Remap Sublime Keymap in EmacsProEssentials - sublimetext3

Question

The EmacsProEssentials Sublime Text 3 package has a bug in the keybindings:
{"keys": ["ctrl+\\"], "command": "undo"}
Undo is not ctrl+\ in Emacs it is ctrl+/.
The developer is aware of the issue, but I'd like to remap the key in the meantime.
How do I remap the key in a package in Sublime Text 3?

Answer 1

When Sublime loads package resource files, it loads similarly named files from all packages and combines them together. This is done in a specific order, and in that order the User package is always last so that your customizations take precedence.
So the easiest thing to do would be to just use Preferences > Key Bindings (this is under Sublime Text if you're on MacOS) and put the fixed binding in your custom key bindings.
Once you do that, your version of the binding will be active (as will the old one from the package), so things will work the way that you expect.
When the upstream author updates the package you can remove your customized binding, although presumably this is not vital if you're both going to make the same change.
The more involved version of the fix involves using PackageResourceViewer to find and open the packaged version of the sublime-keymap and modify it there, thus overriding it and fixing it at the source.
However if you do that, when the author updates the file your change will still take precedence without any notification otherwise, so you'll be effectively locking yourself into your modified version, which could conceivably cause troubles down the line.
You can mitigate that by also installing OverrideAudit, which will tell you when this sort of thing is happening, but fixing it in your User package is probably the better way regardless.