Build of Kotlin examples fails with Nix on Linux

[msgilligan]

build gradle is failing for me on NixOS, both in my home-manager shell and in a nix develop shell.

The error is:

> Task :secp-examples-kotlin:compileKotlin FAILED
e: No class roots are found in the JDK path: /nix/store/j4miw9k22ivwmga8hibwh3cph601z2nc-openjdk-22.0.2-ga

I can work around it by installing a Gradle wrapper and using the Gradle wrapper to launch Gradle or by commenting out the Kotlin module in settings.gradle.

It seems to be related to these commented out lines in flake.nix:

(mkIf stdenv.isLinux [
       {
              name = "JAVA_HOME";
              eval = "$DEVSHELL_DIR/lib/openjdk";
       }
   ])

I think "jdk home" or "JAVA_HOME" is not being set correctly in the Kotlin plugin when a Nix-installed Gradle is being used and the correct JDK path should be (in the case of the error message above):

/nix/store/j4miw9k22ivwmga8hibwh3cph601z2nc-openjdk-22.0.2-ga/lib/openjdk

[msgilligan]

It's also worth noting that the Kotlin plugin version 2.0.20 says it is not compatible with Gradle 8.10 (it says 8.6 for best results, but 8.7-8.8 should also work) I haven't found Gradle 8.10 to cause problems in any other case on either macOS or Linux.

[msgilligan]

You can build the Kotlin examples on NixOS with the master branch (as of today) but only by using ./gradlew. To build using a Gradle provided by Nixpkgs, you'll have to wait until Gradle 8.11 is available there. See: NixOS/nixpkgs#355951

[msgilligan]

Update. This problem may also occur when using nixpkgs on Linux, but does not occur on macOS.

I have opened an issue on the Nixpkgs repo: NixOS/nixpkgs#360954

The workaround of replacing the jdk23 package with the the temurin-bin-23 package seems to be the best short-term solution. I will make a PR to do that, but we will leave this issue open until we get a fix that lets us use a jdk23 (or later) that is build from source.