Haskell Servant - is there a way to compose API types?

Question

I know this isn't valid syntax, but is there a way to accomplish something like this in servant?

type StandardAPI = "foo" :> Get '[JSON] Whatever

type CustomAPI = StandardAPI :<|> "customroute" :> Get '[JSON] Blah

in other words, composing APIs. In Spock I could do this with the monadic route construction, but I'm not sure how to do this in servant.

This way I can reuse shared routes across APIs. Another reason to use this is that there are certain types that don't work with client generators, such as Raw.

Answer 1

Yes, referencing Servant documentation you can use

type CombinedAPI = "users" :> UsersAPI
          :<|> "products" :> ProductsAPI

server :: Server CombinedAPI
server = usersServer :<|> productsServer

usersServer :: Server UsersAPI
usersServer = -- implementation

productsServer :: Server ProductsAPI
productsServer = -- implementation