Apparently there's now a wrapper for libfswatch: [https://github.com/FedericoCeratto/nim-fswatch](https://github.com/FedericoCeratto/nim-fswatch)
While no help to you, maybe it's interesting for someone else reading this. I ported over fsmonitor to modern asyncdispatch in February, since I quickly had to hack together an online event display. But it only supports linux, same as the old fsmonitor. [https://github.com/Vindaar/fsmonitor2](https://github.com/Vindaar/fsmonitor2) However, looking at the File System Event API for OSX, adding support doesn't seem all that complicated: [https://developer.apple.com/library/archive/documentation/Darwin/Conceptual/FSEvents_ProgGuide/UsingtheFSEventsFramework/UsingtheFSEventsFramework.html](https://developer.apple.com/library/archive/documentation/Darwin/Conceptual/FSEvents_ProgGuide/UsingtheFSEventsFramework/UsingtheFSEventsFramework.html) I don't have a Mac, so attempting that would be a pain. Sounds like a fun weekend project for someone to attempt though. :)
