Run tests with Java 8 without rebuilding all dependencies with Java 8

[Christopher Kilian]

Hello!

We currently build our codebase with a Java 11 toolchain but use the Jaebel plugin to make the byte code compatible with Java 8. We have a few test classes that need to run with Java 8 due to incompatibilities with Java 11.

I am aware that we can set a config setting in bazelrc to build with Java 8, but this will cause all dependencies of the target to be rebuilt with Java 8 as well. We want to build everything with Java 11 but just have the test run Java 8 at runtime.

scala_rules made this very easy by providing the runtime_jdk (https://github.com/bazelbuild/rules_scala/blob/94fdc8183caf8f6ae49e33bf06a0bc13fef181e3/scala/private/rules/scala_junit_test.bzl#L76) field as an input to the scala_junit_test rule. There doesn't seem to be an equivalent in the java_test rule, but I'm hoping it might be possible to recreate something similar.

java_test has the launcher field which seems like it may be applicable, but I am having trouble finding any documentation or examples on how to create a launcher. This would also not be an optimal way for us to do this, as the launcher must be a cc_binary and we have no other C++ code in our codebase. If this is the only option, could someone point me in the direction of how to create one?

Thank you!

Chris

[Christopher Kilian]

Bumping this

[Christopher Kilian]

Another bump. We're exploring the idea of extending the BazelTestRunner class and passing it as the "main_class" parameter. Interested in other ideas.

[Xudong Yang]

cc Ivo & Hemanshu

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