Select a default jdk implementation in a nix-shell derivation

1

Hi,

I would like to experiment with clojure and its build tool leiningen with a modern jdk; the default jdk implementation is currently java 8 and I’m not able to switch to another jdk implementation inside a nix-shell.
I’m using the following default.nix

let
   pkgs = import <nixpkgs> {};
   newPkgs = pkgs // {jdk = pkgs.adoptopenjdk-jre-openj9-bin-11;};
in 
with newPkgs;
stdenv.mkDerivation {
  name = "clojure";
  nativeBuildInputs = [
    jdk
    lumo     
    leiningen
    clojure
  ];
  buildInputs = [
    openssl
    
  ];  
}

when I’m running nix-shell it is using the selected jdk

$ java -version
openjdk version "11.0.3" 2019-04-16
OpenJDK Runtime Environment AdoptOpenJDK (build 11.0.3+7)
Eclipse OpenJ9 VM AdoptOpenJDK (build openj9-0.14.0, JRE 11 Linux amd64-64-Bit Compressed References 20190417_202 (JIT enabled, AOT enabled)
OpenJ9   - bad1d4d06
OMR      - 4a4278e6
JCL      - 5cc996a803 based on jdk-11.0.3+7)

but leiningen is still running with java 8

$ lein -version
Leiningen 2.9.1 on Java 1.8.0_212 OpenJDK 64-Bit Server VM

as it is set inside the wrapper script

$ cat `which lein`
#! /nix/store/cinw572b38aln37glr0zb8lxwrgaffl4-bash-4.4-p23/bin/bash -e
export PATH='/nix/store/lhnmfhvw0zlhrd56gp13h2ajbmg51cjh-rlwrap-0.43/bin:/nix/store/d9s1kq1bnwqgxwcvv4zrc36ysnxg8gv7-coreutils-8.30/bin'${PATH:+':'}$PATH
export LEIN_GPG='/nix/store/mqynspckwdp0ymalay32wb7pa7x3hpax-gnupg1compat-2.2.13/bin/gpg'
export JAVA_CMD='/nix/store/gp1avksany5bilwm4vj6nz0vv8cc7wx5-openjdk-8u212-ga/bin/java'
exec -a "$0" "/nix/store/20rpcd8pc7krpfn9ca7p5rgmiwbmgn7r-leiningen-2.9.1/bin/.lein-wrapped"  "${extraFlagsArray[@]}" "$@"

How can I change the default jdk to a different version and have all build tools use the new version?

Thanks

2

This is where overlays are useful. For instance, this would use the same jdk everywhere:

let
  pkgs = import <nixpkgs> { overlays = [ (self: super: {
    jdk = super.adoptopenjdk-jre-openj9-bin-11;
  }) ]; };
in
with pkgs;
stdenv.mkDerivation {
  name = "clojure";
  nativeBuildInputs = [
    jdk
    lumo
    leiningen
    clojure
  ];
  buildInputs = [
    openssl
  ];
}

You have to be careful that this approach isn’t a mass rebuild (for instance, overriding something like stdenv will mean you must rebuild everything). But for jdk, it works well (the example above rebuilds clojure, leiningen, and lumo).

2 Likes
3

Perfect, exactly what I was expecting from my configuration.

Thanks!

4

how would you achive this in a configuration.nix file? I’m always confused by the fact that the syntax differs between nix-shell and .nix files…

Being a complete noob at nix, i came up with this:

newPkgs = with pkgs; { overlays = [ (self: super: {
    jdk = super.adoptopenjdk-jre-openj9-bin-11;
  }) ]; };
   environment.systemPackages = with newPkgs; [
    jdk
  ];

but that gives me the error “undefined variable newPkgs at line such and such”

all my other attempts end up installing java 8 when I need 11 or later

1 Like
5

I too wonder where one would go to clarify this. Especially with overlays, it seems like the syntax is different…

6

The syntax of the language does not change.

Only the way how you apply an overlay changes, as you are in a different context.

In home.nix or configuration.nix you need to use nixpkgs.overlays option rather than to overwrite or create a new pkgs variable, which wouldn’t be used in that context anyway.