The router crashes when the body is a JSON array

[weppos]

I was able to reproduce the error here.

  1) Error:
Body parsing#test_0002_is successful (JSON) with an array:
TypeError: no implicit conversion of Array into Hash
    /Users/weppos/Mirrors/hanami--router/lib/hanami/routing/parsers.rb:49:in `merge!'
    /Users/weppos/Mirrors/hanami--router/lib/hanami/routing/parsers.rb:49:in `block in _redefine_call'
    /Users/weppos/Mirrors/hanami--router/lib/hanami/routing/http_router.rb:135:in `raw_call'
    /Users/weppos/.rvm/gems/ruby-2.3.0/gems/http_router-0.11.2/lib/http_router.rb:142:in `call'
    /Users/weppos/Mirrors/hanami--router/lib/hanami/router.rb:931:in `call'
    /Users/weppos/.rvm/gems/ruby-2.3.0/gems/rack-1.6.4/lib/rack/lint.rb:49:in `_call'
    /Users/weppos/.rvm/gems/ruby-2.3.0/gems/rack-1.6.4/lib/rack/lint.rb:37:in `call'
    /Users/weppos/.rvm/gems/ruby-2.3.0/gems/rack-1.6.4/lib/rack/mock.rb:74:in `request'
    /Users/weppos/.rvm/gems/ruby-2.3.0/gems/rack-1.6.4/lib/rack/mock.rb:59:in `patch'
    /Users/weppos/Mirrors/hanami--router/test/integration/body_parsing_test.rb:27:in `block (2 levels) in <top (required)>'

  it 'is successful (JSON) with an array' do
    body     = StringIO.new( %(["alpha", "beta"]).encode(Encoding::ASCII_8BIT) )
    response = @app.patch('/books/23', 'CONTENT_TYPE' => 'application/json', 'rack.input' => body, lint: true)

    response.status.must_equal 200
    response.body.must_equal %(["alpha", "beta"])
  end

This is an example of a request

$ curl http://example.com/path -X POST -d '["alpha", "beta"]' -H "Content-Type: application/json"

Of course, the tricky part is how this case should be handled in the params as it implies the params can also be an Array, instead of always a Hash.

It's possible to use a constant key, for example _, which is also the same approach Rails is following.

{"_json"=>["ns1.example.com", "ns2.example.com"], "controller"=>"something", "action"=>"create", "something"=>{"_json"=>["ns1.example.com", "ns2.example.com"]}}

In this case, Rails uses the _json key.

FYI, Lotus crashes at this point, because merge! can't handle an input which is not a Hash.

          env[ROUTER_PARAMS].merge!(
            @parsers[
              media_type(env)
            ].parse(body)
          )