gradle: Decouple from JDK 8 and support Java Toolchains

[lorenzleutgeb]

This sets a default Java installation per Gradle version, and allows to specify Java Toolchains.

Gradle Version	Attribute	Default Java Version	defaultJava
7.3	gradle_7	17	jdk8
6.9.1	gradle_6	11	jdk11
5.6.4	gradle_5	11	jdk11
4.10.3	gradle_4	8	jdk8

(see also Gradle's Compatibility Matrix)

E.g. with gradle_7.override { javaToolchains = [ jdk8 jdk11 ]; } I get

$ gradle -q javaToolchains

 + Options
     | Auto-detection:     Enabled
     | Auto-download:      Enabled

 + N/A JDK 17.0.1+12-nixos
     | Location:           /nix/store/1vi5p9gliab13jc3v56kz7z78x5bq0da-openjdk-17.0.1+12/lib/openjdk
     | Language Version:   17
     | Vendor:             N/A
     | Is JDK:             true
     | Detected by:        Current JVM

 + OpenJDK 1.8.0_272-b10
     | Location:           /nix/store/4f0d8c9lmj174hz3qvn1qhc70n22bai4-openjdk-8u272-b10
     | Language Version:   8
     | Vendor:             Oracle
     | Is JDK:             true
     | Detected by:        environment variable 'JAVA_TOOLCHAIN_NIX_0'

 + OpenJDK 11.0.12+0-adhoc..source
     | Location:           /nix/store/7r5b2r4kjsbflgxs8sy7i86c1wy773is-openjdk-11.0.12+7
     | Language Version:   11
     | Vendor:             Oracle
     | Is JDK:             true
     | Detected by:        environment variable 'JAVA_TOOLCHAIN_NIX_1'

[SuperSandro2000]

Hey, @SuperSandro2000 I hope you don't mind me pinging you after ~2weeks.

You can ping me if you have a question but it can take me a few days to answer if you are unlucky.

I'd still like to get this PR merged and would appreciate your advice on how we can get it done 🚀 😃 Any other changes to make?

ofborg is red because something does not eval correct. I don't really know why from ofborgs log. Maybe nix-env -f . -qaP --show-trace gives something more useful?

[SuperSandro2000]

expect it to eval now.

ofborg has a different opinion on that. I am not sure why it fails now but I assume the variable is not a derivation but I can't really help your with that.

[stale]

I marked this as stale due to inactivity. → More info

[lorenzleutgeb]

Pinging @tadfisher to review with respect to gradle2nix compatibility. I tried to keep everything compatible:

• gradleGen will default to defaultJava = jdk8 if it's not given (but it would be a good idea to pass something better).
• gradleGen is still exposed (even though I originally wanted to remove it).

[lorenzleutgeb]

Deleting this override is okay, because gradle_6 now uses jdk11 by default.

[lorenzleutgeb]

Deleting this override is okay, because gradle (which is the latest Gradle) currently uses jdk17, which is currently equal to jdk, by default.

[marvin-mk2]

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[kevincox]

It looks like all concerns have been addressed. If any remain they can be fixed in post.

[Profpatsch]

This PR completely broke the gradleGen interface, breaking gradle2nix tadfisher/gradle2nix#53

[lorenzleutgeb]

@Profpatsch yes. I did not understand that this PR would break gradle2nix. My apologies. I tried to reach @tadfisher, as evidenced in #119444 (comment) but never received a response. Overall I think that this PR still provided some convenient features. Thanks to @Mic92 for cleaning up.

[coderfromhere]

@lorenzleutgeb What's the proper way to use gradleGen with jdk overrides in the new interface? I.e. what would be the new solution for something like this:

{ jdk }:
{
  packageOverrides = p: {
    gradle = (p.gradleGen.override {
      java = p.${jdk};
    }).gradle_latest;
  };
}

[lorenzleutgeb]

@coderfromhere Very sorry to take so long to reply.

Instead of using packageOverrides, I'd suggest using overlays. An overlay to use the latest version of Gradle with a given JDK would look like this:

(self: super: {
  gradle = super.gradle.override { inherit java; };
})

The above example requires a variable java to reference the JDK. An overlay without such a parameter could look like this:

(self: super: {
  gradle = super.gradle.override { java = super.jdk8; };
})

See also the arguments here.

[nixos-discourse]

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/auto-detecting-java-installations/4677/9