Can't generate scalar JSON in gqlgen - json

Question

I have a GQL scheme:
extend type MyType #key(fields: "id") {
id: ID! #external
properties: JSON #external
myField: String! #requires(fields: "properties")
}
scalar JSON
In graph/model/model.go:
package model
import (
"encoding/json"
"fmt"
"io"
"strconv"
"strings"
)
type JSON map[string]interface{}
// UnmarshalGQL implements the graphql.Unmarshaler interface
func (b *JSON) UnmarshalGQL(v interface{}) error {
*b = make(map[string]interface{})
byteData, err := json.Marshal(v)
if err != nil {
panic("FAIL WHILE MARSHAL SCHEME")
}
tmp := make(map[string]interface{})
err = json.Unmarshal(byteData, &tmp)
if err != nil {
panic("FAIL WHILE UNMARSHAL SCHEME")
//return fmt.Errorf("%v", err)
}
*b = tmp
return nil
}
// MarshalGQL implements the graphql.Marshaler interface
func (b JSON) MarshalGQL(w io.Writer) {
byteData, err := json.Marshal(b)
if err != nil {
panic("FAIL WHILE MARSHAL SCHEME")
}
_, _ = w.Write(byteData)
}
But when I run go run github.com/99designs/gqlgen generate
error:
generating core failed: type.gotpl: template: type.gotpl:52:28: executing "type.gotpl" at <$type.Elem.GO>: nil pointer evaluating *config.TypeReference.
GOexit status 1
I just need to get map[string]interface{} which called JSON. I knew there's scalar Map, but for apollo federation that field must be called JSON.

Answer 1

it's should to replace MarshalGQL to MarshalJSON like:
type JSON map[string]interface{}
func MarshalJSON(b JSON) graphql.Marshaler {
return graphql.WriterFunc(func(w io.Writer) {
byteData, err := json.Marshal(b)
if err != nil {
log.Printf("FAIL WHILE MARSHAL JSON %v\n", string(byteData))
}
_, err = w.Write(byteData)
if err != nil {
log.Printf("FAIL WHILE WRITE DATA %v\n", string(byteData))
}
})
}
func UnmarshalJSON(v interface{}) (JSON, error) {
byteData, err := json.Marshal(v)
if err != nil {
return JSON{}, fmt.Errorf("FAIL WHILE MARSHAL SCHEME")
}
tmp := make(map[string]interface{})
err = json.Unmarshal(byteData, &tmp)
if err != nil {
return JSON{}, fmt.Errorf("FAIL WHILE UNMARSHAL SCHEME")
}
return tmp, nil
}