Custom route, but keep some routes as the automatic ones

Question

I've added a few Actions on top of the CRUD ones, and I want to have custom routes to the new actions. But still, keep the CRUD actions with the same route (e.g. /ShowPost?postId=[uuid]

instance HasPath PostsController where
    -- ...
    pathTo ShowPostAction { postId } = "/ShowPost?postId=" ++ tshow postId


instance CanRoute PostsController where
   parseRoute' = do
       let posts = do
           string "/Posts"
           optional "/"
           endOfInput
           pure PostsAction

       let showPost = do
           string "/ShowPost?postId="
           postId <- parseId
           optional "/"
           endOfInput
           pure ShowPostAction { postId }


       posts <|> showPosts -- ...

I assume the CanRoute part isn't parsing correctly, as I end up with a 404 page when navigating to /ShowPost?postId=...

Answer 1

The problem here is that the ?postId= is not part of the request path directly as it's part of the query string of the request.

Given a request like /ShowPost?postId=abc, then the parser input is actually just /ShowPost. The ?postId=abc is available through the ?context variable only.

You could try something like this (not tested):

instance HasPath PostsController where
    -- ...
    pathTo ShowPostAction { postId } = "/ShowPost?postId=" ++ tshow postId

-- Define the auto route instance
instance AutoRoute PostsController

instance CanRoute PostsController where
   parseRoute' = do
       let customRoutes = ...
       customRoutes <|> (autoRoute @PostsController)

Basically this would use your customRoutes parser first and then try to fallback to the parser by AutoRoute.