When doing handler composition, there seems to be a regression in Falco 4 which causes

I just rolled out a fix for this. Huge shoutout to <a class="user-mention notranslate"

<a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/us

Falco 4 handler not responding correctly. about falco HOT 3 CLOSED

pimbrouwers commented on July 4, 2024

Falco 4 handler not responding correctly.

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Comments (3)

pimbrouwers commented on July 4, 2024 5

I just rolled out a fix for this. Huge shoutout to @mlaily for the discovery.

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seangwright commented on July 4, 2024 1

@sheridanchris I noticed this same behavior when doing async/Task work with Request.mapForm in v4.0.

You can see in this discussion how I had to adopt a different approach (lower-level) to compose my async work with the APIs Falco provides.

Here's two approaches I ended up trying that both work.

Approach 1 - `Request.mapFormAsync`

  let post: HttpHandler =
    Services.inject<ShopContext> (fun db ->

      let mapAsync = fun (form: FormCollectionReader) ->
        form.TryGetGuid "id"
        |> BasketDomain.updateBasket db 1
        |> Async.StartAsTask

      Request.mapFormAsync mapAsync (fun quantity ->
        match quantity with
        | None -> Response.redirectPermanently "/basket?error=notfound"
        | Some q -> Response.redirectPermanently $"/basket?added={q}"))

where Request.mapFormAsync was something I added:

module Request =
  open System.Threading.Tasks
  open Microsoft.AspNetCore.Http
  open Falco

  let mapFormAsync
    (mapAsync : FormCollectionReader -> Task<'T>)
    (next : 'T -> HttpHandler) =
    fun (ctx: HttpContext) -> (task {
      let! form = Request.getForm ctx
      let! res = mapAsync form
      return! next res ctx
    }:> Task)

Approach 2 - `Request.getForm`

  let postAlternate: HttpHandler =
    Services.inject<ShopContext> (fun db -> fun ctx ->
      task {
        let! form = Request.getForm ctx

        let productId = form.TryGetGuid "id"

        let! quantity = BasketDomain.updateBasket db 1 productId |> Async.StartAsTask

        return!
          match quantity with
          | Some q -> Response.redirectPermanently $"/basket?added={q}" ctx
          | None -> Response.redirectPermanently "/basket?error=notfound" ctx
      })