Json.Decode.decodeString never succeeds when input is empty string

[jinjor]

For SSCCE:

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

main : Html
main = text <| toString <| Json.decodeString decoder ""

decoder : Decoder String
decoder =
  Json.succeed "Succeed!"

This shows:

Err ("Unexpected end of input")

I ran into this problem when I used Http.post and tried to decode response (which is empty string). This issue may be related to this issue.

[jvoigtlaender]

It was noted on the mailing list that this is not a bug, but instead the expected behavior, since the emtpy string is not valid JSON.

[jvoigtlaender]

It was noted on the mailing list that this is not a bug, but instead the expected behavior, since the emtpy string is not valid JSON.

[jinjor]

Ah, now I understand. Thank you.
The real problem here was "I assumed Json.Decode.succeed always succeeds even if given JSON is invalid", but it was wrong.

[jinjor]

Ah, now I understand. Thank you.
The real problem here was "I assumed Json.Decode.succeed always succeeds even if given JSON is invalid", but it was wrong.

[jvoigtlaender]

I think the documentation could be more helpful, to prevent such misunderstandings. I opened https://github.com/elm-lang/core/issues/613.

[jvoigtlaender]

I think the documentation could be more helpful, to prevent such misunderstandings. I opened https://github.com/elm-lang/core/issues/613.

[jinjor]

Seems good :)

[jinjor]

Seems good :)