package main

import (
        "fmt"
        "io"
        "log/slog"
)

type Name struct {
        First, Last string
}

// LogValue implements slog.LogValuer.
// It returns a group containing the fields of
// the Name, so that they appear together in the log output.
func (n Name) LogValue() slog.Value {
        return slog.GroupValue(
                slog.String("first", n.First),
                slog.String("last", n.Last))
}

func main() {

        l := slog.New(slog.NewTextHandler(io.Discard, &slog.HandlerOptions{
                ReplaceAttr: func(groups []string, a slog.Attr) slog.Attr {
                        fmt.Println(a.Key, a.Value.Kind())
                        return a
                },
        }))

        n := Name{"Perry", "Platypus"}
        l.Info("mission accomplished", "agent", n)
}

time Time
level Any
msg String
first String
last String

time Time
level Any
msg String
agent Group // <-- this call should not happen
first String
last String