Dear community,
Goal and problem
I’ve tried to set up a developer environment for a project where I need Java (zulu8) and SBT. If I don’t override any settings, SBT will use its default JRE. As we use zulu8, I tried overriding the JRE setting in SBT, but this was unsuccessful.
Trials
I tried setting this:
sbt.override { jre = pkgs.zulu8; }
and the whole flake then looks like this:
{
description = "A flake for getting started with Scala (Zulu8 JDK) & scala-cli.";
inputs.nixpkgs.url = "github:nixos/nixpkgs";
inputs.flake-utils.url = "github:numtide/flake-utils";
outputs = { nixpkgs, flake-utils, ... }:
let
supportedSystems = [
"aarch64-darwin"
"aarch64-linux"
"x86_64-linux"
"x86_64-darwin"
];
in
flake-utils.lib.eachSystem supportedSystems (
system: let
pkgs = import nixpkgs { inherit system; };
sbt8 = pkgs.sbt.override { jre = pkgs.zulu8; };
in
{
devShells.default = pkgs.mkShell {
packages = with pkgs; [ scalafmt zulu8 scala-cli ];
};
formatter = pkgs.default.alejandra;
}
);
}
If I use this, and run sbt , then I get the output
[info] welcome to sbt 1.7.1 (Azul Systems, Inc. Java 11.0.18)
which is the same as when I set the override to (note the removed ‘8’ from behind ‘zulu’):
sbt8 = pkgs.sbt.override { jre = pkgs.zulu; };
So I think something’s going wrong there between the zulu versions or with SBT not accepting older Java versions as override, but I can’t solve it. Could anyone provide some insights? 
Current workaround
FYI, I currently work around this issue by explicitly passing the Java directory that I want to SBT: sbt -java-home $JAVA_HOME, which shows that this does work and now successfully uses zulu8:
[info] welcome to sbt 1.7.1 (Azul Systems, Inc. Java 1.8.0_362)
Thanks in advance for any help!