At Almost Human Ltd. one my tasks has been rewriting and implementing new features to the rapid development environment which has been used in the creation of the Legend of Grimrock 2 game. The environment allows adding and modifying Lua code on the fly: No code recompiling is needed and usually even restarting the game is unnecessary.
The older proprietary in-house made code editor was replaced with Sublime Text 3 which supports Python extension scripts. First I ported all the functionality of the old editor to Sublime Text extensions and after that I have added new features whenever the need has arisen. The development system uses TCP localhost communication and features include for example text output window, method completion, method name searching, static analysis and code folding via key shortcuts.
The rapid_sublime plugin can be downloaded from https://github.com/almosthumangames/rapid_sublime. It has been released with MIT license, so poke around as much as you want. It really has no use without the proprietary server-side code but it has some scripts that can be easily modified to your own use.