Elm, JSON decoder: How to decode an empty string?

Question

What's the best way to handle an empty (no string at all) response?

Although the response code is 200, Elm returns an error because an empty response is not a valid JSON.

Here is my current code:

decodeAlwaysTrue : Json.Decode.Decoder Bool
decodeAlwaysTrue =
  Json.Decode.succeed True

Http.send Http.defaultSettings httpConfig
  |> Http.fromJson decodeAlwaysTrue
  |> Task.perform FetchFail DeleteUserSuccess

EDIT1:

This a POST action so I can't use getString.

Answer 1

You could use the getString function from the Http module. That will give you back whatever string is returned from the HTTP request without attempting to convert is to a Json value.

If you instead need to use Http.send then you could do something like this:

Http.send Http.defaultSettings httpConfig
  |> Task.perform FetchFail (always DeleteUserSuccess)

This assumes that DeleteUserSuccess is changed to be defined with no type parameter:

type Msg =
  ...
  DeleteUserSuccess