Invoked maven should be executed in same java environment as rascal itself

[DavyLandman]

We call maven from within rascal, this assumes first that maven is installed, and that java is installed.

But if a user installed maven, and has a JAVA_HOME pointing to java 8, but starting rascal with a different JDK (either via java_home, or via path, an explicit path, or vscode auto install) the invoked mvn is running in a different version of java.

In some setups (like for example the vscode auto install) this can cause problems.

We should, when invoking mvn, copy our own java.home property onto the environement of the mvn call. Note #1661 also solves this issue, since it doesn't fork to maven anymore.

thanks @djswagerman for taking the time to test it out and report the issue.

[jurgenvinju]

will mvn always use JAVA_HOME or will we use the mvn in the PATH with a given JAVA_HOME?

[jurgenvinju]

is this the issue where clair would not work with a difference JRE?

[DavyLandman]

will mvn always use JAVA_HOME or will we use the mvn in the PATH with a given JAVA_HOME?

• when rascal starts mvn it should be on it's path (this is a limitation of the vscode auto installer of java, it's not bringing along a maven install), again Rework maven code for faster calculation of path config #1661 fixes that, and otherwise we would need to do some changes on how the maven executable is found.
• maven's command line util says:

# -----------------------------------------------------------------------------
# Apache Maven Startup Script
#
# Environment Variable Prerequisites
#
#   JAVA_HOME       Must point at your Java Development Kit installation.

and looking at the code, java on your path is not enough, it should have a valid JAVA_HOME. This PR just makes sure that JAVA_HOME is correctly setup, and points to the same jdk as rascal is running under. Since rascal can be started by a JVM that is not defined in the JAVA_HOME env.

is this the issue where clair would not work with a difference JRE?

I don't know that specific issue. But I think @djswagerman could tell you if this was the same problem.