Test Rake on TruffleRuby

[eregon]

• See truffleruby is broken with rake test suite oracle/truffleruby#1739
  and f19222f.

cc @hsbt

[eregon]

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

[eregon]

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

[eregon]

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.

[eregon]

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)

[hsbt]

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

[eregon]

@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.

[eregon]

I just merged oracle/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]

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

👍