Missing fields when marshaling a struct with an inlined structs and Custom BSON Marshaling

[alco...@gmail.com]

When marshaling a struct with an inline struct that has custom BSON marshaling, some of the fields in the "parent" struct don't get marshaled.

Here is the minimal code to reproduce the problem:

package main

import (
    "fmt"
    "log"
    "reflect"

    "gopkg.in/mgo.v2/bson"
)

type Person struct {
    Name string
}

func (p *Person) GetBSON() (interface{}, error) {
    return struct {
        Name string
    }{
        Name: p.Name,
    }, nil
}

type Student struct {
    Person `bson:",inline"`
    Course string
}

func main() {
    s := &Student{
        Person: Person{Name: "Alberto"},
        Course: "math",
    }

    bytes, err := bson.Marshal(s)
    if err != nil {
        log.Fatal("marshaling: ", err)
    }

    ss := &Student{}
    if err := bson.Unmarshal(bytes, ss); err != nil {
        log.Fatal("unmarshaling: ", err)
    }

    if !reflect.DeepEqual(s, ss) {
        fmt.Println("ERROR: students differ!")
        fmt.Println(s)
        fmt.Println(ss)
    } else {
        fmt.Println("OK: students are the same!")
    }
}

The code above compares and student before and after marshal/unmarshal.  The student after the marshaling is missing the specific fields of the Student struct (i.e. "courses") and only has the fields in the inlined struct ("Person.Name").

If I comment out the "Person.GetBSON" method, the code works just fine, and the student is equal before and after the marshal/unmarshal.

Wha I'm doing wrong?

[alco...@gmail.com]

A few more comments:

- When I execute the code from the previous post, I get:

ERROR: students differ!
&{{Alberto} math}
&{{Alberto} }

- If I comment out the "Person.GetBSON" method and execute, I get the expected, correct, behaviour:

OK: students are the same!

- I'm using "gopkg.in/mgo.v2/bson" commit 3f83fa5005286a7fe593b055f0d7771a7dce4655 (Aug 17, 2016)

- i get the same results using "github.com/globalsign/mgo/bson" commit 896bbb89d21253a28cd5a7f8b81fe091410cb94d (Jan 15, 2018)