Documentation

The HeaderList combinator provides a list of Network.HTTP.Types.Header.Header values from the WAI request.

Example:

import Control.Monad.IO.Class (liftIO)
import Servant
import ServantExtras.HeaderList

import qualified Network.HTTP.Types.Header as NTH (Header)

type MyAPI = "my-header-endpoint"
           :> HeaderList
           :> Get '[JSON] NoContent

myServer :: Server MyAPI
myServer = headerEndpointHandler
 where
   headerEndpointHandler :: [NTH.Header] -> Handler NoContent
   headerEndpointHandler headers =
      let mCookieValue = lookup "merlinWasHere" headers in
      case mCookieValue of
       Nothing -> do
         liftIO $ print "Merlin was *NOT* here!"
         throwError err400 { errBody = "Clearly you've missed something." }
       Just message -> do
         liftIO $ do
           print "Merlin WAS here, and he left us a message!"
           print message
         pure NoContent