Objects loaded via Marshal don't get Java class applied corrected unless passed through fn taking exact type

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When a Ruby object is returned from a Java interface method, it is casted to the return type, even though in this case the Ruby class is made to implement the interface. So when the return type is Object JRuby essentially does nothing.

This might be a bug, but it's hard to tell. The Ruby object hasn't been converted to a Java object before so the JRuby internals aren't noticing that it can or should be converted to a Java object/interface implementation.

The class has been declared to implement that interface, so I would have expected the instance to implement it, regardless of the signature of the method which was called.

It's a problem for my application because it has a method which returns 'anything', which could be stuff like java.lang.Number or classes implemented in Ruby. The Java side then makes sense of it and does the right thing.

Different Java classes are returned depending on what code has run before, which made it amusing to track down.

I have worked around this by calling a Java function which expects an object of the right type just after the base class is defined, and this has resolved the issue.

Also, if you don't run the object through Marshal, it works as I would expect.

There's different behaviour when you create the object through Klass.new and via Marshal.load(), which can't be right?

Checked it in master, still fails.

$ jruby -v
jruby 1.6.0.dev (ruby 1.8.7 patchlevel 330) (2011-01-06 16aa9c5) (Java HotSpot(TM) Client VM 1.6.0_22) [SunOS-x86-java]
$ ./run.sh
classViaCreating, class = org.jruby.RubyObject
functionTakingObject, class = ImplementingClass_277712892
functionTakingObject, class = ImplementingClass_277712892

I think this is a simple matter of forcing unmarshaling to trigger any delayed JI class setup. I'll poke around.

I'm only fixing this in 1.7, since it's somewhat old and the change is more invasive than I'd like for 1.6.x.

Here's the commit. I need a JI spec, and more testing would be most welcome.

commit 284ab7dc07b09623e63acdaaa2b1b397c1a86b15
Author: Charles Oliver Nutter <headius@headius.com>
Date:   Mon Jan 9 13:35:13 2012 -0600

    Fix JRUBY-5317.
    
    Objects loaded via Marshal don't get Java class applied corrected unless passed through fn taking exact type
    
    The problem here was that Marshal uses allocate to create objects
    coming in, but all our logic for initializing JI-related subclasses
    lived in "new". By moving that logic to allocate we clean up both
    the "new" stuff (no need for custom method anymore) and also ensure
    the logic runs regardless of whether you "new" or "allocate" the
    object.
    
    I have run our tests, but it would be helpful to get more cases
    surrounding Marshal and have user codebases run with this patch
    in place.