[BUG] Gradle fails to find a Java compiler on Raspberry Pi 4/CM4

[megatog615]

Describe the bug
Trying to compile PCGen git on my CM4-based device on Raspberry Pi OS/testing(which is basically Debian aarch64), gradlew build fails trying to find a Java installation despite having openjdk-21-jdk(-headless) installed locally.

To Reproduce
Steps to reproduce the behavior:

1. Install Raspberry Pi OS on a Raspberry Pi (or virtual machine)
2. Switch to testing (change 'bookworm' to 'testing' in /etc/apt/sources)
3. apt update
4. apt install openjdk-21-jdk-headless
5. get the pcgen git sources
6. ./gradlew

Expected behavior
I expected gradle to use openjdk 21 to compile fine, or download the appropriate toolchain if it needed to as I am used to it doing in the past.

Log

FAILURE: Build failed with an exception.

* Where:
Build file '/home/***/src/git/pcgen/build.gradle' line: 306

* What went wrong:
A problem occurred evaluating root project 'pcgen'.
> Could not resolve all dependencies for configuration ':runtimeClasspath'.
   > Failed to calculate the value of task ':compileJava' property 'javaCompiler'.
      > Cannot find a Java installation on your machine matching this tasks requirements: {languageVersion=21, vendor=any vendor, implementation=vendor-specific} for LINUX on aarch64.
         > No locally installed toolchains match and toolchain download repositories have not been configured.

* Try:
> Learn more about toolchain auto-detection at https://docs.gradle.org/8.10.2/userguide/toolchains.html#sec:auto_detection.
> Learn more about toolchain repositories at https://docs.gradle.org/8.10.2/userguide/toolchains.html#sub:download_repositories.
> 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.

BUILD FAILED in 3s
[2:28 PM]

Desktop:

• OS: Raspberry Pi OS testing
• Raspberry Pi Compute Module 4

Additional context
./gradlew downloadJRE also fails with the same error.

[karianna]

That seems like a core Gradle env detection bug, have you reported this to them?

[megatog615]

No. By the way, I noticed that inside of /usr/lib/jvm there is java-21-openjdk-arm64 but not java-21-openjdk-aarch64. AFAIK aarch64 and arm64 are the same thing so I made a symbolic link changing arm64 to aarch64 and gradlew actually makes it past. So this is definitely a bug. Not sure if a workaround can be used in the PCGen gradle config files.

Didn't finish compiling though but still, that's progress.

[megatog615]

There is indeed an issue for this for Gradle.