Grape API w/ Versioning Fallback

A Grape API mounted on Rack with two versions where v2 builds incrementally on top of v1. In this example the ping method is only implemented on version v1, while the root method is implemented on both versions.

Run

$ bundle install
$ rackup

Try

# without a version

curl http://localhost:9292/
{"version":"v2"}

curl http://localhost:9292/ping
{"ping":"pong"}

# version v2 (current)

curl http://localhost:9292 -H "Accept:application/vnd.acme-v2+json"
{"version":"v2"}

curl http://localhost:9292/ping -H "Accept:application/vnd.acme-v2+json"
{"ping":"pong"}

# version v1 (old)

curl http://localhost:9292 -H "Accept:application/vnd.acme-v1+json"
{"version":"v1"}

curl http://localhost:9292/ping -H "Accept:application/vnd.acme-v1+json"
{"ping":"pong"}