MarshalYAML doesn't call MarshalYAML on returned value

[rogpeppe]

From reading the docs, I'd expect the following example to print "something",
but it prints "y": 99 instead.

package main

import (
    "fmt"
    "log"
    "gopkg.in/yaml.v2"
)

func main() {
    t := T{99}
    data, err := yaml.Marshal(t)
    if err != nil {
        log.Fatal(err)
    }
    fmt.Printf("%s\n", data)
}

type T struct {
    X int
}

func (t T) MarshalYAML() (interface{}, error) {
    return S{t.X}, nil
}

type S struct {
    Y int
}

func (s S) MarshalYAML() (interface{}, error) {
    return "something", nil
}

[niemeyer]

Interested in offering a patch for this?

[sigmonsays]

I am interested in getting this fixed too. +1

[rogpeppe]

I'd love to do a patch but there are at least 10 things that I need to do more than this that I know no-one else is ever going to do... Perhaps on a flight sometime, unless I find this bug blocking some other task.

[josephbuchma]

Why MarshalYAML method of Marshaler interface returns interface{} rather than []byte like in encoding/json ?

[ghost]

We ran into this. Is this something you'd consider a bug or just inaccurate documentation?

[niemeyer]

The expectation sounds reasonable, so tastes more like a bug than desired behavior.

I'm about to release v3 publicly, which is a good chance to get this fixed as it might break compatibility otherwise. I'll look into this.

[niemeyer]

This is fixed in v3. Will close the issue once v3 is announced.

[metux]

According to the source, this should be solved at least in v3.
Shall the issue be marked resolved ?

[arykalin]

I'm using v3 and MarshalYAML is still no called.
UPD: sorry. MarshalYAML is not working only if use pointer receiver. Without pointer it's working