Parse query string comma-separated values as list

[cmeeren]

I'd like to deserialize the query string ?flags=favorite,hidden to the type Query as defined below:

type Flag = Favorite | Hidden
type Query = {Flags: Flag list}

Is this possible using Giraffe? I've only managed to use lists in query strings by repeating the parameter: ?flags=favorite&flags=hidden.

(Please disregard the actual DU related stuff; I've fixed that by using FSharpLu.Json.)

[dustinmoris]

Hi @cmeeren, the way list items are passed through a query string is by specifying the parameter multiple times like in your second example. See #121 (comment)

In this case ASP.NET Core has already decomposed the query string into a list and Giraffe is simply deserializing the string values into the correct type.

Your client application has to send list items in the correct format I am afraid.

EDIT: You could do your own hack by having a type like this:

type Flag =
    | Favorite
    | Hidden

type Query =
    {
        Flags : string
    }
    member this.FlagList =
        this.Flags.Split ','
        |> Array.map (fun s ->
            match s with
            | "hidden"   -> Hidden
            | "favorite" -> Favorite
            | _ -> failwithf "Could not deserialize string '%s'." s)
        |> Array.toList

[cmeeren]

Thanks for the tip. I too was under the impression that specifying the parameter multiple times was the correct way, but our front-end developer suggested using comma-separated values, so I just wanted to check if this was something Giraffe supported. It seems we should indeed stick to the standard way of doing things.

[cmeeren]

On the other hand, the JSON API spec specifies that comma-separated values is mandatory behavior (link to first mention). Do you think it would be possible and desirable for Giraffe to add support for this?

[narve]

On the other hand, the JSON API spec specifies that comma-separated values is mandatory behavior (link to first mention). Do you think it would be possible and desirable for Giraffe to add support for this?

Good point - although I don't like JSON APIs specification, it should be easy to follow it.
Has this been resolved, or an easier workaround found?

[cmeeren]

I am splitting manually.

As a side note, I have also created FSharp.JsonApi, which makes JSON:API much more pleasant to use with F# (and optionally Giraffe). It has (among many other things) built-in helpers for parsing comma-separated query strings. (Don't use the package just for that feature, though.)

[narve]

All right, thanks for the info!