No diff output when matching strings that differ in trailing newlines

[phiggins]

If I have a spec like this:

$ cat test_spec.rb 
describe "test case" do
  it "diffs its arguments" do
    expect("foo\n").to eq("foo")
  end
end

When I run it I get output like this:

pete@balloon:~/projects/rspec-support$ rspec test_spec.rb 
Run options: include {:focus=>true}

All examples were filtered out; ignoring {:focus=>true}

test case
  diffs its arguments (FAILED - 1)

Failures:

  1) test case diffs its arguments
     Failure/Error: expect("foo\n").to eq("foo")

       expected: "foo"
            got: "foo\n"

       (compared using ==)

       Diff:

     # /home/pete/projects/rspec-expectations/lib/rspec/expectations/fail_with.rb:33:in `fail_with'
     # /home/pete/projects/rspec-expectations/lib/rspec/expectations/handler.rb:36:in `handle_failure'
     # /home/pete/projects/rspec-expectations/lib/rspec/expectations/handler.rb:49:in `handle_matcher'
     # /home/pete/projects/rspec-expectations/lib/rspec/expectations/expectation_target.rb:54:in `to'
     # ./test_spec.rb:3:in `block (2 levels) in <top (required)>'
     # /home/pete/projects/rspec-core/lib/rspec/core/example.rb:148:in `instance_exec'
     # /home/pete/projects/rspec-core/lib/rspec/core/example.rb:148:in `block in run'
     # /home/pete/projects/rspec-core/lib/rspec/core/example.rb:299:in `with_around_example_hooks'
     # /home/pete/projects/rspec-core/lib/rspec/core/example.rb:145:in `run'
     # /home/pete/projects/rspec-core/lib/rspec/core/example_group.rb:494:in `block in run_examples'
     # /home/pete/projects/rspec-core/lib/rspec/core/example_group.rb:490:in `map'
     # /home/pete/projects/rspec-core/lib/rspec/core/example_group.rb:490:in `run_examples'
     # /home/pete/projects/rspec-core/lib/rspec/core/example_group.rb:457:in `run'
     # /home/pete/projects/rspec-core/lib/rspec/core/runner.rb:112:in `block (2 levels) in run_specs'
     # /home/pete/projects/rspec-core/lib/rspec/core/runner.rb:112:in `map'
     # /home/pete/projects/rspec-core/lib/rspec/core/runner.rb:112:in `block in run_specs'
     # /home/pete/projects/rspec-core/lib/rspec/core/reporter.rb:54:in `report'
     # /home/pete/projects/rspec-core/lib/rspec/core/runner.rb:108:in `run_specs'
     # /home/pete/projects/rspec-core/lib/rspec/core/runner.rb:86:in `run'
     # /home/pete/projects/rspec-core/lib/rspec/core/runner.rb:70:in `run'
     # /home/pete/projects/rspec-core/lib/rspec/core/runner.rb:38:in `invoke'
     # /home/pete/projects/rspec-core/exe/rspec:4:in `<top (required)>'
     # /home/pete/.rvm/gems/ruby-2.1.2@rspec-support/bin/rspec:23:in `load'
     # /home/pete/.rvm/gems/ruby-2.1.2@rspec-support/bin/rspec:23:in `<main>'
     # /home/pete/.rvm/gems/ruby-2.1.2@rspec-support/bin/ruby_executable_hooks:15:in `eval'
     # /home/pete/.rvm/gems/ruby-2.1.2@rspec-support/bin/ruby_executable_hooks:15:in `<main>'

Finished in 0.00133 seconds (files took 0.08229 seconds to load)
1 example, 1 failure

Failed examples:

rspec ./test_spec.rb:2 # test case diffs its arguments

Randomized with seed 29283

The output indicates that there should be a diff but no diff is present. See also rspec/rspec-support#70.