Change XmlNodeSet#to_a return type to RubyArray

[headius]

The existing signature conflicts with one added to JRuby 9.2.9.
Specifically, the new signature in JRuby returns RubyArray, which
causes a compilation error on this line in Nokogiri because it
attempts to use a more general return type.

We would prefer to keep the specific return type in JRuby.

• If we patch JRuby, then 9.2.9 will never be able to compile any
  version of Nokogiri.
• If we patch Nokogiri, all versions of JRuby can compile current
  and future Nokogiri. Versions prior to 9.2.9 will be able to
  compile all existing releases of Nokogiri.

I do not believe the change in 9.2.9 breaks anything at runtime,
since the JVM does not care about this particular return type
mismatch unless someone actually returns a non-RubyArray object.

Fixes #1968

[jvshahid]

The changes look good to me. I don't think the failures are related to the change. The failure was in the MRI valgrind tests. I am waiting to see the tests pass before I merge the PR.

[flavorjones]

Yeah, looks like some optimizations were backported to ruby 2.5, so I just added a valgrind suppression and will kick off again.

[flavorjones]

@headius I see you based this commit on the v1.10.x branch. For future reference, we ask that people send PRs against master, and then we can cherry-pick onto the v1.10.x branch if we need to cut a release.

I'm not totally familiar with the JRuby 9.2.9 change that is driving this commit, but am I to understand that you're requesting a bug fix release in the v1.10.x series?

[flavorjones]

Remaining CI failure is due to #1971, looking into it. We could merge this PR, but I'd like to leave it open for a bit so I can ensure the CI job is stable.

[headius]

@flavorjones In JRuby 9.2.8, the only to_a defined on our RubyBasicObject class was RubyArray to_a(). In JRuby 9.2.9, we added RubyArray to_a(ThreadContext). Nokogiri's XmlNodeSet previously defined a IRubyObject to_a(ThreadContext) signature. Since XmlNodeSet descends from RubyBasicObject, method signatures it overrides need to be compatible. In this case, because IRubyObject is a the more generic interface type than RubyArray, it fails to compile.

So the addition of the new to_a in JRuby broke compilation of Nokogiri because Java. At runtime it probably doesn't matter since the XmlNodeSet#to_a still returns a RubyArray, but the compiler doesn't like the signatures not matching.

This fix should go into any active Nokogiri branches going forward. I did not do the PR against master because it appear to be behind the branch.

[flavorjones]

@headius Going forward please submit PRs based on master, thanks.

[flavorjones]

Merged manually onto master. Will be in v1.11.0. Thank so much, @headius!

[flavorjones]

Side note: this actually went out in v1.10.9, see https://my.diffend.io/gems/nokogiri/1.10.8-java/1.10.9-java

[headius]

@headius Going forward please submit PRs based on master, thanks.

A suggestion: put this in the project PR template, perhaps?

Thanks for merge and release!

[flavorjones]

@headius Great minds think alike: 787fed8 🤣

Thanks again.