Trailing slashes in CaptureAll router behave unpredictably

[isovector]

Consider the following program:

{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE TypeApplications  #-}

module Repo where

import Control.Monad.Except (throwError)
import Data.List (isSuffixOf)
import Data.Proxy (Proxy(..))
import Data.Text (Text)
import GHC.Generics (Generic)
import Network.HTTP.Types.Header (hLocation)
import Network.Wai.Handler.Warp (run)
import Servant.API
import Servant.Links
import Servant.Server


data API mode = API
  { myroute :: mode :- "test" :> CaptureAll "segs" Text :> Get '[JSON] [Text]
  }
  deriving Generic

server :: [Text] -> Handler [Text]
server ts =
  case isSuffixOf [""] ts of
    False ->
      throwError err303
        { errHeaders = pure
            ( hLocation
            , mappend "/" $ toHeader $ fieldLink myroute $ ts <> [""]
            )
        }
    True -> pure ts

main :: IO ()
main = run 8081 $ serve (Proxy @(NamedRoutes API)) $ API server

which 303 redirects test/:stuff to test/:stuff/. This works when :stuff is nonempty, eg test/abc correctly gets redirected to test/abc/ (and returns ["abc", ""]).

However, when :stuff is empty, this server loops, redirecting the page back to itself:

Request

GET /test/ HTTP/1.1
Host: localhost:8081
Pragma: no-cache

---

Response

HTTP/1.1 303 See Other
Location: /test/