instance_spy breaks when using accessors in JRuby

[doozr]

When using JRuby 1.7.19 it is impossible to assign attributes when using instance_spy. The attributes work fine when using an instance_double as a null object. The test case is:

class SingleAccessor

  attr_accessor :should_be_assignable

end

describe SingleAccessor do

  it "allows an instance_spy accessor to be assigned" do
    instance_spy("SingleAccessor").should_be_assignable = "value"
  end

  it "allows a double as null object accessor to be assigned" do
    double("SingleAccessor").as_null_object.should_be_assignable = "value"
  end

end

With this result:

Failures:

  1) SingleAccessor allows an instance_spy accessor to be assigned
   Failure/Error: instance_spy("SingleAccessor").should_be_assignable = "value"
   ArgumentError:
     Wrong number of arguments. Expected 0, got 1.
   # ./spec/assign_to_mock_accessor_spec.rb:10:in `(root)'
   # ./spec/spec_helper.rb:96:in `(root)'
   # ./spec/spec_helper.rb:96:in `(root)'

Finished in 0.023 seconds (files took 1.62 seconds to load)
2 examples, 1 failure

Failed examples:

rspec ./spec/assign_to_mock_accessor_spec.rb:9 # SingleAccessor allows an instance_spy accessor to be assigned

The following versions are used:

jruby 1.7.19 (1.9.3p551) 2015-01-29 20786bd on Java HotSpot(TM) 64-Bit Server VM 1.6.0_31-b04 +jit [linux-amd64]
rspec 3.2.3
rspec-mocks 3.2.1

It worked fine with rspec 3.1.7 and rspec-mocks 3.1.3

[myronmarston]

This is due to a bug in JRuby -- see the issue linked above. It worked fine on rspec-mocks 3.1 because on 3.0 and 3.1 we weren't verifying arguments for calls to null-object doubles. #829 fixed that but has the side effect of not working in this case on JRuby due to the JRuby bug.

The attributes work fine when using an instance_double as a null object.

Actually, it fails for instance_double(...).as_null_object, too (which is a relief: that's all instance_spy is so it was confusing me that it would fail for one but not the other!). Your spec above uses double(...).as_null_object, which is not a verifying double.

I'm not sure what to do about this yet...if the runtime lies to us and tells us a method takes no parameters, how are we supposed to know it's lied to us?

[myronmarston]

Hmm, looks like the arity is still correct on JRuby...maybe we can use that.

[doozr]

Ah, my mistake. Yes, you are correct, it doesn't work with instance_double either. My apologies. I'll keep an eye on the JRuby bug.

[myronmarston]

It appears that JRuby does not have this bug when you manually define the writer method (e.g. def should_be_assignable=(value); @should_be_assignable = value; end), so you might switch to that while we keep thinking about if we're going to do anything to work around this.

[myronmarston]

Looks like jruby/jruby#2816 has already been fixed! They've added it to the JRuby 1.7.20 milestone which suggests a fix will come in the next JRuby 1.7 release.

Given that it's being addressed in JRuby so promptly, I don't think we should expend effort to work around it. Closing.

[doozr]

Good to know! For the time being I'll leave my 1 unchecked double (it's not critical to the test anyway) but will let the team know about the manual definition workaround. Cheers.

[betesh]

I'm running a jruby-1.7.22 Rails app with the following rspec versions:

$ git grep rspec --  Gemfile.lock  | grep "(3\.5"
Gemfile.lock:    rspec (3.5.0)
Gemfile.lock:    rspec-core (3.5.1)
Gemfile.lock:    rspec-expectations (3.5.0)
Gemfile.lock:    rspec-mocks (3.5.0)
Gemfile.lock:    rspec-rails (3.5.1)
Gemfile.lock:    rspec-support (3.5.0)

When I add this line:

mocks.verify_partial_doubles = true

I start getting errors such as this on numerous tests:

   Failure/Error: allow(MyJavaClass).to receive(:some_method).with("One Arg").and_return(some_object)
     Wrong number of arguments. Expected 0, got 1.
   # rspec-support-3.5.0/lib/rspec/support.rb:87:in `Support'
   # org/jruby/RubyProc.java:271:in `call'
   # rspec-support-3.5.0/lib/rspec/support.rb:96:in `notify_failure'
   # rspec-mocks-3.5.0/lib/rspec/mocks/error_generator.rb:327:in `notify'
   # rspec-mocks-3.5.0/lib/rspec/mocks/error_generator.rb:311:in `__raise'
   # rspec-mocks-3.5.0/lib/rspec/mocks/error_generator.rb:119:in `raise_invalid_arguments_error'
   # rspec-mocks-3.5.0/lib/rspec/mocks/verifying_message_expectation.rb:48:in `validate_expected_arguments!'
   # rspec-mocks-3.5.0/lib/rspec/mocks/verifying_proxy.rb:186:in `with_signature'
   # rspec-mocks-3.5.0/lib/rspec/mocks/verifying_message_expectation.rb:40:in `validate_expected_arguments!'
   # rspec-mocks-3.5.0/lib/rspec/mocks/verifying_message_expectation.rb:27:in `with'

My workaround is to add this to spec/spec_helper.rb, above RSpec.configure do |config|:

RSpec::Support.require_rspec_support 'ruby_features'
module RSpec::Support::RubyFeatures
  module_function
  def optional_and_splat_args_supported?
    false
  end
end

This fixed all the tests except the ones that use allow/expect_any_instance_of (at least on my dev machine--it did not fix it on my CI server, probably because we're running rspec slightly differently there and may have already loaded rspec-mocks before this method is redefined).