The bug

Upon attempting to launch an installation with its directory set to a directory that the user does not have access to, the launcher silently fails to launch the game. By this, I mean that no error message is presented. The launcher doesn't even seem to realize that it has failed to launch the installation, as when trying to open another installation, the game says 'Already joined the game as this user' and presents users with the option to cancel the launch of the new installation. This proves that the launcher thinks that it has succeeded in launching the other installation.

Attempting to launch another installation in a valid directory and selecting 'Start anyway' when presented with the warning message does not do anything, as the Launcher is still trying to launch the game in the private directory.

Trying to quit the program by using the Command+Q shortcut or from the menu bar freezes the program, and the Force Quit menu must be utilized to recover.

How to reproduce

1. Run the following commands in Terminal:

   cd ~/Desktop
   mkdir TestFolder
   chmod 000 TestFolder 

1. Open the Minecraft Launcher -> Installations -> New...
2. Set the game directory to the folder TestPrivate (that you have just created) and create the installation
3. Navigate to the Play tab, and select the installation you have just created
4. Click 'Play'
   Observe the failure

Additional information

This was tested on four different operating systems:

• OS X Yosemite 10.10.5
• macOS High Sierra 10.13.6
• macOS Big Sur 11.0
• macOS Big Sur 11.1

A video of this issue occurring can be found here.