json: cannot unmarshal string into Go value of type multiaddr.Multiaddr

[mg98]

I'm having trouble to unmarshal JSONs to structs that include Multiaddr fields.

json: cannot unmarshal string into Go struct field .a of type multiaddr.Multiaddr

var d struct {
	A ma.Multiaddr `json:"a"`
}
if err := json.Unmarshal([]byte(`{"a":"/ip4/64.227.126.216/tcp/4001"}`), &d); err != nil {
	panic(err)
}

Go Playground

I think it can be further minimized to unmarshaling only the string itself:

var a ma.Multiaddr
b := []byte(`"/ip4/64.227.126.216/tcp/4001"`)
if err := json.Unmarshal(b, &a); err != nil {
	panic(err)
}

Here I'm getting json: cannot unmarshal string into Go value of type multiaddr.Multiaddr.

I see implementations of json marshaling in ma.Multiaddr, so I wonder if I'm doing something wrong?

[mg98]

Hmm I see already, it must be because ma.Multiaddr is an interface and the exact type is not known.

[mg98]

Would like to reopen this... I highly advocate getting rid of the interface here and just sticking with a struct.
Also found in relation to this issue: #100

[marten-seemann]

👋 libp2p maintainer here.

I suggest closing this issue, since this seems to be exactly what #100 is about.

The core team won't have any capacity to resolve this issue any time soon, but we're happy to review a proposal and a PR. @mg98, would you mind commenting on #100 how exactly you'd like to solve this, so we can get the discussion going?