I'm using macOS Mojave, go 1.12.4
Example: https://play.golang.org/p/uluBecqL6QF
I would expect the key and value in the example to be the same.
If you implement TextMarshaler on a custom string type, the encoder does
not use the marshaler when encoding map keys of that type. I ran into this
trying to use bson.ObjectId from the globalsign mgo repo as a key in a map
and trying to serialize it to JSON. The JSON encoder uses reflection to
check that the 'kind' of the value is a string, which is true. But it does
not check if it is a custom string type that has TextMarshaler implemented.
The JSON encoder code:
encoding/json/encode.go 865-884
func (w *reflectWithString) resolve() error {
if w.v.Kind() == reflect.String {
w.s = w.v.String()
return nil
}
if tm, ok := w.v.Interface().(encoding.TextMarshaler); ok {
buf, err := tm.MarshalText()
w.s = string(buf)
return err
}
switch w.v.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
w.s = strconv.FormatInt(w.v.Int(), 10)
return nil
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32,
reflect.Uint64, reflect.Uintptr:
w.s = strconv.FormatUint(w.v.Uint(), 10)
return nil
}
panic("unexpected map key type")
}
Is this intentional?
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