One error on this run: https://github.com/ruby/rake/pull/331/checks?check_run_id=314340711

  1) Error:
TestRakeClean#test_clean:
NoMethodError: undefined method `desc' for #<#<Class:0x5600>:0x33168>
    /home/runner/work/rake/rake/lib/rake/clean.rb:68:in `<top (required)>'
    /home/runner/work/rake/rake/test/test_rake_clean.rb:7:in `load'
    /home/runner/work/rake/rake/test/test_rake_clean.rb:7:in `block in load'
    /home/runner/work/rake/rake/test/test_rake_clean.rb:7:in `each'
    /home/runner/work/rake/rake/test/test_rake_clean.rb:7:in `load'
    /home/runner/work/rake/rake/test/test_rake_clean.rb:7:in `test_clean'

590 runs, 1629 assertions, 0 failures, 1 errors, 0 skips

The issue seems to be that load "rake/clean.rb", true sets the top-level self to main in MRI, but to some other class instance on TruffleRuby:
https://github.com/oracle/truffleruby/blob/c3845389c4f38e51283b48a1ea3ccdac4962adbf/src/main/java/org/truffleruby/core/kernel/TruffleKernelNodes.java#L108
cc @chrisseaton

That's a trivial fix (use the main object in both cases), and then I can run all rake locally successfully.

We'll need a nightly build of TruffleRuby to test in CI though, or skip that load "rake/clean.rb", true test until then.

It's actually not the same main object but some sort of copy of the normal main, including modules in the singleton class of the original main.

In Ruby terms:

wrap_module = Module.new
new_main = main.clone # make a copy of the singleton class and the methods there
new_main.extend(wrap_module)

@eregon Thanks for your work. I'm okay to merge when CI was fixed.

@hsbt The CI now passes, with that test slightly modified when running on TruffleRuby 19.3.0, is that acceptable? (18508c4)
I think it would be useful to test TruffleRuby in Rake's CI from now, and not need to wait for the next release.

I just merged truffleruby/truffleruby@f054b32, which fixes load(path, wrap=true) on TruffleRuby.
But that is not part of the 19.3.0 release of course, it will only be in the 20.0.0 release.

@hsbt The CI now passes, with that test slightly modified when running on TruffleRuby 19.3.0, is that acceptable? (18508c4)

👍