Proguard preventing build using JDK 17 (Cannot support JDK 8 and 17)

Problem

Using JDK java 17.0.1 2021-10-19 LTS and Gradle 7.3

When I run ./gradlew build I get the following…

> Task :proguardJar FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':proguardJar'.
> java.io.IOException: Can't read [/home/theman/Applications/Java/jdk-17.0.1/jmods] (Can't read [jdk.jstatd.jmod] (Can't process class [module-info.class] (Unsupported version number [61.0] (maximum 60.65535, Java 16))))

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

It seems proguard should support this at least in Beta (https://github.com/Guardsquare/proguard/issues/132) so it should probably be upgraded to support 17 builds.

Current workaround

I am guessing I can use the 16 JDK but I don’t have time to try that rt now. I will setup a diff JDK shortly to confirm.

Sorry if I did this wrong new to contributing here.

Per @modmuss50 we cannot just upgrade proguard

[modmuss50]

Yes, for now you need to use JDK 16.

The version of PG that supports 17 does not support Java 8 anymore hence why its using the version it is.

I should be able to set it up to use the older build on JDK 8 and the newer build on 17 to keep support for building loader with JDK 8 -> 17

[modmuss50]

I have opened a PR here: https://github.com/FabricMC/fabric-loader/pull/555 that should hopefully fix it.