remote_coverage_tools requires JDK 11

[nacl]

Description of the bug:

Our build uses JDK 8 to run tools and build binaries. Bazel itself and a sizeable amount of the precompiled tools are compiled using JDK 11, however, the Bazel java_tools are compiled with JDK 8 and work fine in our setup.

The remote_coverage_tools binaries, however, are precompiled using JDK 11, resulting in the following stacktrace in our setup:

Error: A JNI error has occurred, please check your installation and try again
Exception in thread "main" java.lang.UnsupportedClassVersionError: com/google/devtools/coverageoutputgenerator/Main has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:757)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:468)
        at java.net.URLClassLoader.access$100(URLClassLoader.java:74)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:369)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:363)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:362)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:419)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:365)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:352)
        at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:601)

To maintain JDK 8 compatibility (if desired), it would seem that the remote_coverage_tools should be built targeting JDK 8, or the sources made available as a part of the Bazel binary distribution

What's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

In Bazel itself:

bazel coverage --java_language_version=8 --tool_java_language_version=8 --java_runtime_version=8 --tool_java_runtime_version=8 //src/tools/singlejar:output_jar_simple_test

Will have this stack trace in the logs.

The build fails with JDK 8 in recent 7.0.0-pre builds due to (apparently) incompatible changes. A different example may needed for that purpose.

Which operating system are you running Bazel on?

Linux, Alma 9 (RHEL-like), arm64

What is the output of bazel info release?

release 6.1.0rc1 (also reproduces with 6.0.0)

If bazel info release returns development version or (@non-git), tell us how you built Bazel.

No response

What's the output of git remote get-url origin; git rev-parse master; git rev-parse HEAD ?

No response

Have you found anything relevant by searching the web?

• Bazel 6.0.0 Java 8 Coverage Broken #17165 refers to use of the java 11 runner to build against java 8 targets. We are using Java 8 everywhere.
• Running coverage on a py_test fails when --java_runtime_version is Java 8 #17568 is python-specific
• @bazel_tools//tools/java/runfiles:auto_bazel_repository_processor does not compile with JDK 8 #17458 is specific to the runfiles library

Any other information, logs, or outputs that you want to share?

No response

[nacl]

This issue seems to be the direct result of the upgrade to coverage_output_generator 2.6 in a70d84b. 2.5 seems to have been compiled targeting JDK 8.

[thirtyseven]

@nacl Bazel uses a separate JRE to run java tools like remote_coverage_tools, this is what --tool_java_language_version and --tool_java_runtime_version control. Is there any reason you also need them to be set to Java 8? In our Java 8 project, we have them set to the default of 11 with no issues.

[nacl]

@thirtyseven I am aware of those flags, but unfortunately we have numerous other java tools that are untested with Java 11. I agree that it will probably be fine, but if anything does come up it may become difficult to address the problems in a timely manner, as the people who might need to be involved have their own priorities/timetables/etc.

FWIW, I was able to compile these tools targeting Java 8 in our private build of Bazel with no issue, and coverage reports were generated as expected.