Custom game versions or modloaders (such as Fabric) that use the "inheritsFrom" key in the version json no longer start the game and leave the launcher in a broken state.

Recently we (Fabric) have had a large number of players contacting us about being unable to start their modded versions of Minecraft. When clicking play a toast is shown saying "Unable to start Minecraft" and the launcher is left in a broken/un-useable state. (See: screenshots)

After looking into this I was able to reproduce this without the use of a mod loader by creating a simple custom version. It appears the issue only happens when you have not previously used the Minecraft version that the custom version inherits from. The expected and previous behavour allowed the launcher to download the vanilla version as required.

Steps to reproduce:

1. Start with a fresh install of the launcher, or ensure that the vanilla version behing inherited from has not been started previously.

2. Save the following file to .minecraft/versions/test.json :

{
    "id": "test",
    "inheritsFrom": "1.19.2",
    "releaseTime": "2022-12-08T16:30:33+0000",
    "time": "2022-12-08T16:30:33+0000",
    "type": "release"
} 

3. Create a new instance using this version

4. Click play on the new instance and notice the toast error and the game does not start.

5. Notice under "Installations" all installations are suck "Waiting to install"

This can be fixed by fully closing the launcher, creating a new instance with vanilla 1.19.2 starting the game, and then the modded/custom instance will work. I have been able to reproduce this in the none beta version of the Windows and MacOS launchers.

Please let me know if you require any more information or details. A swift resolution would be highly appreciated due to the severity of this issue.