Eliom_parameter.sum is broken on Eliom 4.1

[darioteixeira]

It seems that Eliom_parameter.sum does not work with Eliom 4.1 (the server returns a 500 error and always complains about wrong parameters). I don't know exactly when this regression was introduced, but IIRC this feature worked fine on Eliom 3. Here is a minimal example that illustrates the problem:

open Eliom_content.Html5.F
open Eliom_parameter

let coucou_handler sum () =
    let msg = match sum with Inj1 s -> s | Inj2 i -> string_of_int i in
    Lwt.return
        (html
            (head (title (pcdata "Coucou")) [])
            (body [p [pcdata "You sent: "; pcdata msg]]))

let coucou_service =
    Eliom_registration.Html5.register_service
        ~path:["coucou"]
        ~get_params:Eliom_parameter.(sum (string "s") (int "i"))
        coucou_handler

let main_handler () () =
    Lwt.return
        (html
            (head (title (pcdata "Main")) [])
            (body
                [
                h1 [pcdata "Links for coucou:"];
                p [a coucou_service [pcdata "Inj1 (string)"] (Inj1 "testing")];
                p [a coucou_service [pcdata "Inj2 (int)"] (Inj2 123)];
                ]))

let main_service =
    Eliom_registration.Html5.register_service
        ~path:[]
        ~get_params:Eliom_parameter.unit
        main_handler

[Drup]

I can reproduce, but I really don't know what's going on.

[darioteixeira]

PR #114 seems to be the most recent modification to the code that parses sum parameters. Perhaps @hhugo or @balat know what's going on?

[hhugo]

looking quickly at the code, I wonder if

eliom/src/lib/eliom_parameter.server.ml

Line 263 in 930fdbc

let v,l = (List.assoc_remove (pref^name^suff) params) in

should go inside the try-with

[vasilisp]

I tested @hhugo's hypothesis, and it seems to fix the issue. List.assoc_remove throws Not_found for one of the two cases, and we do not produce Errors_ (as should be the case), but rather the exception bubbles up.

[vbmithr]

@Drup @balat Once this is fixed, we will release a new eliom version.

[balat]

@hhugo Do you remember why you did this? 930fdbc

[balat]

Ok I found. It's related to #45