When I try to launch any minecraft version on that game directory (C:/Users\MyName\Onedrive\Documents\.minecraft), the launcher gives me this error message:

Unable to create directory.
Error details: Impossible de créer un fichier déjà existant
Filename on disk: .minecraft
Path: C:/Users\Bryan\OneDrive\Documents\.minecraft
Exists: true

Translated in English, it means "Can't create already existing file"

Although I understand that minecraft isn't supposed to run on Onedrive, it was working fine till now. So there's no reason it shouldn't work after an update.

It gives me this same error if I copy the .minecraft that is on Onedrive and paste it anywhere else and then change the game directory in my launcher.

Steps tried to avoid the problem, without success:
1) Choose "Always keep on this device" for the destined folder inside OneDrive
2) Starts Minecraft Launcher using "Run as administrator"
3)Launch minecraft while the OneDrive client is completely closed

EDIT:

The error is probably a problem with the new OneDrive on demand file system. It seems like the directories inside OneDrive are actually files, not directories, though you can navigate through them with the file explorer. That's probably why minecraft won't launch, because it sees that there is a file named .minecraft, so it can't create a directory with the same name.

So basically, minecraft can read and write inside files on OneDrive, but everything that is in a directory can't be modified or read.

2nd EDIT:

I can confirm that IT IS NOT a problem that affects all java programs. I just created a small java program that reads a file inside a directory in OneDrive. It can do it without any problems. Also I checked with File().isDirectory() and File().isFile to see if my .minecraft was considered by java as a file and it isn't, java can see that it's a directory.