Safe Decode?

[glennsl]

Safe Decode?

[glennsl]

Hi. What do you mean you can't catch the exception? Have you tried adding a branch for DecodeError to the try block?

      try (decodeState(Json.parseOrRaise(stateStr))) {
        | Json.ParseError(e) => ...
        | Json.Decode.DecodeError(e) => ...
      };

should work fine.

[raqystyle]

@glennsl Json.Decode.DecodeError is what I was missing. Thank you! But I didn't know I had to add this branch as well. The compiler didn't argue back that my check is not exhaustive enough. I'm I missing something?

[raqystyle]

@glennsl Actually, I was mislead (maybe, this word is too strong) by the documentation for the Json.parseOrRaise which states: parse s returns a Js.Json.t if s is a valid json string, raises ParseError otherwise. Anyway, thank you for the help!

[glennsl]

There's unfortunately no exhaustiveness checking for exceptions. Parsing and decoding are different processes, and you need to check for errors from both. It can be a valid json string and still not fit the shape you need, in which case it will raise a DecodeError.

There are libraries that do provide exhaustiveness checking of errors, like JsonR and JsonCodec, but it comes at a cost.

[raqystyle]

@glennsl Oh, I see. Thank you for explanation!