unable to get value of object's fields in RubyMine debugger

[os97673]

Originally filed agains RubyMine (https://youtrack.jetbrains.com/issue/RUBY-15864)
Users basically unable to see value of object's fields.
Here is a simple example which shows how we (ruby-debug-base) try to get value of fields.
It looks like a bug for me, but if it is not please suggest a way to implement similar functionality for jruby.

class Foo
  attr_accessor :test
end

foo = Foo.new
foo.test = 'visible?'
puts foo.test

bindings = ["binding()", "Kernel::binding()", "Object.send(:binding)"].map {|b| foo.instance_eval(b)}
bindings.each do |b|
  puts "--#{eval("@test", b).nil?}--"
end

[os97673]

@headius it would be nice to get your thoughts about the problem

[headius]

Has this ever worked in JRuby? Why aren't you using instance_variable_get?

I suppose it could be a bug, but this is an incredibly weird way to get instance variables out of an object.

[os97673]

Honestly, I do not know I've not seen this working, but I only tested with modern jruby while the code was written long time ago. If you know a better way to get field's value from an object I'm ok to change ruby-debug-base.

[headius]

You should be able to use instance_variables and instance_variable_get on most objects (perhaps not BasicObject) to introspect instance variables. I'm guessing the eval form is done to avoid cases where those methods are unavailable or redefined (e.g. a blank slate object).

I think there's still a bug here, though, since it seems like at least one of these eval forms should have been able to see the @test variable.

[headius]

Ok, a slightly reduced case that should work, but it shows that when we create a binding inside instance_eval it does not get the proper "self".

class Foo
  attr_accessor :test
end

foo = Foo.new
foo.test = 'visible?'
puts foo.test

p eval("self", foo.instance_eval("binding")) # => "main"
p eval("@test", foo.instance_eval("binding")) # => "nil"

[headius]

This is also wrong on master, @enebo @subbuss.

[headius]

I have a likely fix that basically just uses the instance_eval "self" as the frame "self" when pushing a frame in preExecuteUnder. It's a little scary to change, though.

[enebo]

Incidentally I am also posing removing that method altogether on master :) We are pushing 2 scopes in IR one from preExecuteUnder and one by IR interpreter...

[headius]

@enebo that sounds fine too. I'm going to push my change to a test branch and see how Travis test runs handle it before doing something similar for release branches.

[headius]

Pushed my change to branch "test-instance_eval-self-fix-2301" and the travis run is here: https://travis-ci.org/jruby/jruby/builds/44131805. If it passes, this may be an ok fix for both branches, but I will also defer to @enebo since he's working on eval right now on master.

[ninkibah]

I got very excited about this this morning, and upgraded jruby-1.7.17 to jruby-1.7.18.

Sadly, it only fixes part of the problem. Class variables are shown properly, but instance variables are not. :-( I'll raise it again with the rubymine folks.

@headius: Thanks for all your efforts, and have a good Christmas.