Ensure that has_<n> matcher works silently with keyword arguments

[JonRowe]

Alternative to #1184 that doesn't use rspec-support meta magic.

[pirj]

👍 Nice!

[JonRowe]

@pirj @benoittgt how do we feel about this? Realistically the only repetition we could avoid with this approach is the final send with / without keywords, it means a lot more string evals but should be as performant as the original which I know my support branch is not.

Whats interesting is that *args, **kwargs is not the equivalent of *args, as an empty hash is sent if you are not expecting keyword args... hence the if check surrounding empty kwargs.

[pirj]

On 2.7.1 I'm getting this:

  1) expect(...).to be_predicate handles keyword arguments to the predicate
     Failure/Error: raise "Warnings were generated: #{output}" if has_output?

     RuntimeError:
       Warnings were generated: /Users/pirj/source/rspec-dev/repos/rspec-core/lib/rspec/core/example_group.rb:764: warning: Using the last argument as keyword parameters is deprecated; maybe ** should be added to the call
       /Users/pirj/source/rspec-dev/repos/rspec-expectations/lib/rspec/matchers.rb:959: warning: The called method `method_missing' is defined here
...
rspec ./spec/rspec/matchers/built_in/be_spec.rb:84 # expect(...).to be_predicate handles keyword arguments to the predicate

[pirj]

What fails if we remove this?

k={}
def a(x)
end
def b(y, z: 1)
end
a(1, **k)
b(2, **k)

neither of those calls results in a warning 😕

[pirj]

I see the failures, but I'm having hard times understanding it, especially that the ArgumentError isn't raised where it should.

[JonRowe]

It doesn't cause a warning, it sends an extra parameter to some places not expecting it.

[JonRowe]

e.g. splatting keyword arguments, creates keyword arguments, and nil is not {}

[pirj]

you need the master branch of rspec-core to avoid that warning

👍 that recent change slipped my mind.

Got it. So I've played around with it, and it seems that be_predicate() is sending __send__(:predicate, *[], **{}) and **{} goes for a regular parameter as {} 🤦

def m(p)
  puts p
end

__send__(:m, *[], **{})

warning: Passing the keyword argument as the last hash parameter is deprecated
{}

I don't have enough words to express my grief.

[JonRowe]

@pirj you need the master branch of rspec-core to avoid that warning

[benoittgt]

Lot's of binding.eval but the result is clear. LGTM!