unmarshal json fails when set is part of struct

[hujun-open]

it seems json umarshal fails when Set is part of struct, following code produces following error. not sure what did I miss here

I am using github.com/deckarep/golang-set/v2 v2.6.0 and go v1.22.1

{"MapSet":["init"],"Name":"test"}
panic: json: cannot unmarshal array into Go struct field TSet.MapSet of type mapset.Set[string]

code:

package main

import (
    "encoding/json"
    "fmt"

    mapset "github.com/deckarep/golang-set/v2"
)

type TSet struct {
    MapSet mapset.Set[string]
    Name   string
}

func main() {
    s1 := TSet{
        MapSet: mapset.NewSet("init"),
        Name:   "test",
    }
    buf, err := json.Marshal(s1)
    if err != nil {
        panic(err)
    }
    fmt.Println(string(buf))
    s2 := new(TSet)
    err = json.Unmarshal(buf, s2)
    if err != nil {
        panic(err)
    }
    fmt.Printf("%+v\n", *s2)
}

[clarkedb]

This is a duplicate of #122 . See @deckarep's comment https://github.com/deckarep/golang-set/issues/122#issuecomment-1872382278 for a full explanation of why this is currently happening, but the short story is that the UnmarshalJSON function is not defined on the set with a pointer receiver.

As a workaround for now you can add s2.MapSet = mapset.NewSet[string]() after you declare s2 and it seems to work as you can see here: https://go.dev/play/p/NQcs2bSLCR2.

That's not ideal, but it will work for now until the open questions in #122 are resolved.

[hujun-open]

ok, thanks, the workaround works; though it would be nicer to fix this