encoding/json: behaves incorrectly on nested structs with json.RawMessage

[zombor]

Example here: https://play.golang.org/p/lozTmQr8pR

I'd expect all three outputs to be sane json. There should be no errors here.

[minux]

I think it's a misuse of json.RawMessage. what do you expect the output to be for the first marshal call? {"tasks":[{"creds":null}]} is not the correct answer.

[zombor]

Can you explain why? I'd expect similar output to []byte: https://play.golang.org/p/krJb2ZhRVD

[minux]

The content of RawMessage is the raw json data, so it's impossible for a RawMessage to be nil or []byte{}. Think how you can parse a valid json into a RawMessage so that it's nil or []byte{}.

[zombor]

Then why does the last example run fine? There should be some consistency, at the very least.

json.Marshal(json.RawMessage(nil))

Outputs "null"

[minux]

That's because the MarshalJSON method of json.RawMessage is defined on a pointer receiver, so if you pass a json.RawMessage to Marshal, it will be treated the same as a []byte and not as a RawMessage. https://play.golang.org/p/_253EEfKke