int64 aren't properly decoded

[jney]

Isn't int64 supposed to be properly decoded ?

code:

package main

import (
    "bytes"
    "encoding/json"

    "github.com/vmihailenco/msgpack/v5"
)

type Test struct {
    ID int64 `json:"id"`
}

func main() {
    s := `{"id":10}`
    var obj map[string]interface{}
    err := json.Unmarshal([]byte(s), &obj)
    if err != nil {
        panic(err)
    }
    res, err := msgpack.Marshal(&obj)
    if err != nil {
        panic(err)
    }
    var publisher Test
    var buf bytes.Buffer
    buf.Write(res)
    dec := msgpack.NewDecoder(&buf)
    dec.SetCustomStructTag("json")
    err = dec.Decode(&publisher)
    if err != nil {
        panic(err)
    }
}

output:

panic: msgpack: invalid code=cb decoding int64

goroutine 1 [running]:
main.main()
    /wherever/main.go:32 +0x108
exit status 2

version:

require github.com/vmihailenco/msgpack/v5 v5.4.1

[son-masanaka]

Hi jney,
I think the panic happens because encoding/json turns numbers into float64, link:
https://pkg.go.dev/encoding/json#Unmarshal:~:text=for%20JSON%20booleans-,float64%2C%20for%20JSON%20numbers,-string%2C%20for%20JSON
then the decoder won’t accept it for an int64 field. It’s much better to encode and decode using the same schema