Decode fails on empty string

[Richard Osafo]

Hi,

I was decoding an http response (body can be blank) and realized that Decode fails on empty string. Gives the error "Given an invalid JSON: Syntax error". Is this by design or a bug?

import Html exposing (text)
import Json.Decode as Decode exposing (..)

main =
  text <| toString test

test =
  [ succeed "cool"
  , fail "oh"
  , null "what?"
  ]
  |> List.map (flip decodeString "")

If it is by design, what is the recommended way of decoding string that can be blank.

For now, I'm using

    let
      x' =
        if x == "" then "\"\"" else x
    in
      case decodeString decoder x' of
        ...

regards,

Richard.

[Janis Voigtländer]

See https://github.com/elm-lang/core/issues/585. Considered a bug.

​

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[Fedor Nezhivoi]

Empty string isn't valid JSON. Try open Chrome DevTools and write JSON.parse("").

--

Best regards,

Fedor Nezhivoi.

[Janis Voigtländer]

Add this as a comment on the GitHub issue, then?

​

[Richard Osafo]

@Janis

Thanks. It is the same issue. Not a show stopper though since a simple `if` fixes it.

@Fedor

Indeed but in that case, don't you think Json.Decode.succeed and Json.Decode.fail must be updated to point that out? When you do `oneOf` with `succeed` in it, you naturally expect it to work as that is what the documentation says.