Old Fabric versions say to be supported in new versions but are not

[Eatham532]

Hi, not exactly sure where to place this bug as I am guessing it is partially due to the metadadta. I stumbled upon this issue when trying to make my own Minecraft launcher and trying to run 1.20.4 with the fabric version of 0.1.0.48.

The metadata says that this version is supported. View url here. However even your own fabric installer cannot install this version.

Tests (All done running 1.20.4 with loader version 0.1.0.48)

When trying to install using fabric installer v0.11.2:

java.lang.NullPointerException  at net.fabricmc.installer.util.Library. (Library.java:37)  at net.fabricmc.installer.client.ClientInstaller.install(ClientInstaller.java:70)  at net.fabricmc.installer.client.ClientHandler.lambda$doInstall$1(ClientHandler.java:100)  at net.fabricmc.installer.client.ClientHandler$$Lambda$26/117298272.run(Unknown Source)  at java.lang.Thread.run(Thread.java:745)

When using my own launcher that does launch the latest Minecraft and fabric version I get the following error:

Exception in thread "main" java.lang.ClassCastException: class jdk.internal.loader.ClassLoaders$AppClassLoader cannot be cast to class java.net.URLClassLoader (jdk.internal.loader.ClassLoaders$AppClassLoader and java.net.URLClassLoader are in module java.base of loader 'bootstrap')
at net.minecraft.launchwrapper.Launch.(Launch.java:34)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

I tested with two other launchers. Both fail to launch. The Modrinth launcher doesn't give any logs. But GdLauncher gave a similar response to what I got in my launcher.

Exception in thread "main" java.lang.ClassCastException: class jdk.internal.loader.ClassLoaders$AppClassLoader cannot be cast to class java.net.URLClassLoader (jdk.internal.loader.ClassLoaders$AppClassLoader and java.net.URLClassLoader are in module java.base of loader 'bootstrap') at net.minecraft.launchwrapper.Launch.

[modmuss50]

Fabric loader only guarentees backwards compatibility, there is no way we can plan for the future. I do see this an issue, and is possibly something we can solve in metadata v3 as detailed here: FabricMC/fabric-meta#25

[modmuss50]

Going to close this as I dont think there is a lot we can do to dermine what versions are supported or not. Generally always use the latest version.