Java toolchain is not respected about rules_java HOT 2 OPEN

To summarise some points from fmeum's reply on the Bazel issue and my follow-up comment:

It just so happens that Bazel 6 uses a JDK 17 and Bazel 7 uses a JDK 21 for the Java toolchains registered by default. These toolchains use a transition on --java_runtime_version to resolve a matching JDK, which is why you see this additional resolution in the debugger.

It seems this also applies to the versions of rules_java: 6.3.2 uses Java 17 by default, whilst 7.0.4 uses Java 21.

We can use this to resolve the immediate issue by downgrading to 6.3.2 until the migration is complete. However, it is still unclear to me if (or how) we would force version 7.0.6 to use the Java 17 toolchain, rather than the Java 21 toolchain.

from rules_java.

Thought I would leave my comment here for the record:
bazelbuild/bazel#19934 (comment)

I believe the real fix is to add

[
    default_java_toolchain(
        name = "toolchain_java%d" % release,
        configuration = DEFAULT_TOOLCHAIN_CONFIGURATION,
        source_version = "%s" % release,
        target_version = "%s" % release,
+     java_runtime = "@bazel_tools//tools/jdk:toolchain_jdk%d" %release,
    )
    for release in RELEASES
]

And supply the toolchain_jdk for versions 8,9,10,11 (or at least a corresponding @bazel_tools//tools/jdk:remote_jdk{8,9,10}).

This will not work out of the box without it because otherwise you will get

java_runtime attribute of java_toolchain rule @rules_java//toolchains:toolchain_java11: '@bazel_tools//tools/jdk:toolchain_java11' does not have mandatory providers: 'JavaRuntimeInfo'

from rules_java.