[fabienpenso]

I've tried it all and the only real solution is a Linux VM without shared folders, which I'm fine with. The project I booted is used by other colleagues so I tried to make it "generic" and then yes, vagrant copies the file.

As you said (and others in comments) bidirectional syncing with docker-rsync, or using NFS, is one way to have files synchronising but it always ends up being a pain.

I did use cached and delegated but it's nowhere near close to the ideal solution: removing macOS of the equation. At least until Docker find a real fix for those performance issues, if anytime.