Unable to use local java version different from system-wide default for Metals

[matteobilardi]

Describe the bug

In an environment with no access to the internet, where I have both VSCode, the metals extension, java 11 and java 17 already installed, and java 11 is the default system-wide java version, it is not possible to run metals with a Scala project that requires exactly java 11 both for running and building.

To Reproduce
On ubuntu jammy

sudo apt install openjdk-17-jdk openjdk-11-jdk 
sudo update-alternatives --config java // Pick java-11-openjdk as the default java

Install vscode and the metals extension and open a scala project that requires java 11.
Disconnect from the internet.

Expected behavior

Currently, it is possible to set distinct java versions for metals and the project, e.g. via

metals.javaVersion: 17,
metals.javaHome: "/usr/lib/jvm/java-11-openjdk-amd64"

However, this only works if either java 17 is the system-wide java binary available in PATH or if there is an internet connection for coursier to use to download java. I would like to be able to tell metals to use the java version at /usr/lib/jvm/java-17-openjdk-amd64/bin/java to run itself, and the java home at /usr/lib/jvm/java-11-openjdk-amd64 to run the project, while at the same time not having java 17 being the default version of java available in PATH, and without having a connection to the internet. That is, I think that something like the following should be possible

metals.javaPath: "/usr/lib/jvm/java-17-openjdk-amd64/bin/java", // use this for metals
metals.javaHome: "/usr/lib/jvm/java-11-openjdk-amd64" // use this for the scala project

Installation:

• Operating system: Linux
• VSCode version: 1.94
• VSCode extension version: 1.43.0
• Metals version: 1.4.1

Additional context

Search terms

JAVA_HOME, javaVersion, javaHome, coursier, offline

[tgodzik]

Thanks for reporting! We should allow javaPath to be modified by the user. I will take a look at it. As a workaround you can set JAVA_HOME globally or just before starting VS Code from comman line via code .