Anonymous embedded struct field inserted/encoded as empty object in DB

[ereyes01]

I'm hitting an issue where structs with an anonymous time.Time field lose their value when encoded and inserted in the DB. Here is an example illustrating the problem. The code below assumes the following:

• There is a DB called test
• The test DB has an empty table called time_test

package main

import (
    "log"
    "time"

    r "github.com/dancannon/gorethink"
)

type TimeHolder struct {
    time.Time
}

type Post struct {
    Title string
    When  TimeHolder
}

func main() {
    p := Post{
        Title: "A test",
        When:  TimeHolder{time.Now()},
    }

    log.Printf("%+v\n", p)

    session, err := r.Connect(r.ConnectOpts{
        Address:  "localhost:28015",
        Database: "test",
    })
    if err != nil {
        log.Fatal(err)
    }

    response, err := r.DB("test").Table("time_test").Insert(p).RunWrite(session)
    if err != nil {
        log.Fatal(err)
    }

    log.Printf("%+v\n", response)

    cursor, err := r.DB("test").Table("time_test").Run(session)
    if err != nil {
        log.Fatal(err)
    }

    if err := cursor.One(&p); err != nil {
        log.Fatal(err)
    }

    log.Printf("%+v\n", p)
}

The output of this program is:

2016/04/11 04:03:11 {Title:A test When:2016-04-11 04:03:11.156167866 -0500 CDT}
2016/04/11 04:03:11 {Errors:0 Inserted:1 Updated:0 Unchanged:0 Replaced:0 Renamed:0 Skipped:0 Deleted:0 Created:0 DBsCreated:0 TablesCreated:0 Dropped:0 DBsDropped:0 TablesDropped:0 GeneratedKeys:[e766b90f-46fc-4f97-9dbf-84c214fddd5e] FirstError: ConfigChanges:[] Changes:[]}
2016/04/11 04:03:11 {Title:A test When:0001-01-01 00:00:00 +0000 UTC}

As you can see, p.Post.When (a TimeHolder type that just holds an anonymous time.Time field) is retrieved with the zero time value despite having been initialized with the current time. In the DB's web UI, or via the Python driver, the Post.When field can be seen with an empty object:

{
"Title":  "A test" ,
"When": { } ,
"id":  "2e0c7937-db70-40ae-8547-4bd9d5bc6cb5"
}

I haven't tested whether anonymous struct fields in general are an issue, or whether the problem is just limited to time.Time values (which I presume may be a bit special). It's getting late (or early) over here :-) ...maybe I can explore further later.

Let me know if I'm doing something wrong, or if this is a real issue.

Thanks, Eddy

[ereyes01]

I also tried just straight up aliasing the time.Time type instead of nesting it as an anonymous struct field. However, the result was similar:

package main

import (
    "log"
    "time"

    r "github.com/dancannon/gorethink"
)

type TimeHolder time.Time

type Post struct {
    Title string
    When  TimeHolder
}

func main() {
    p := Post{
        Title: "A test",
        When:  TimeHolder(time.Now()),
    }

    log.Printf("%+v\n", p)

    session, err := r.Connect(r.ConnectOpts{
        Address:  "localhost:28015",
        Database: "test",
    })
    if err != nil {
        log.Fatal(err)
    }

    response, err := r.DB("test").Table("time_test").Insert(p).RunWrite(session)
    if err != nil {
        log.Fatal(err)
    }

    log.Printf("%+v\n", response)

    cursor, err := r.DB("test").Table("time_test").Run(session)
    if err != nil {
        log.Fatal(err)
    }

    if err := cursor.One(&p); err != nil {
        log.Fatal(err)
    }

    log.Printf("%+v\n", p)
}

Output:

2016/04/11 04:07:27 {Title:A test When:{sec:63595962447 nsec:738681696 loc:0x8e6b80}}
2016/04/11 04:07:27 {Errors:0 Inserted:1 Updated:0 Unchanged:0 Replaced:0 Renamed:0 Skipped:0 Deleted:0 Created:0 DBsCreated:0 TablesCreated:0 Dropped:0 DBsDropped:0 TablesDropped:0 GeneratedKeys:[cbc5d603-3a96-47a4-8404-cb67dd47c2f6] FirstError: ConfigChanges:[] Changes:[]}
2016/04/11 04:07:27 {Title:A test When:{sec:0 nsec:0 loc:<nil>}}

Object in the RethinkDB web UI:

{
"Title":  "A test" ,
"When": { } ,
"id":  "82f22868-5472-4f00-9ce6-5e1ff70be2c3"
}

Thanks again, Eddy

[dancannon]

Hey, thanks for the bug report. I had a quick look at the issue and was able to replicate it myself. However I am not sure if this will be easy to fix without causing performance issues.

In a related note I tried encoding the same struct with encoding/json and got the same result which makes me think that if the stdlib doesnt support this structure maybe GoRethink shouldnt either. What do you think? I will have a more indepth look into this issue later today.

Here is the code I ran:

package main

import (
    "log"
    "time"
    "encoding/json"
)

type TimeHolder time.Time

type Post struct {
    Title string
    When  TimeHolder
}

func main() {
    p := Post{
        Title: "A test",
        When:  TimeHolder(time.Now()),
    }

    log.Printf("%+v\n", p)

    b, err := json.Marshal(p)
    if err != nil {
        log.Fatalln(err)
    }

    log.Printf("%+v\n", string(b))
}

[ereyes01]

Thanks for the quick reply!

You are correct that when time.Time is aliased as another type, it JSON Marshals to the zero value due to this new type not implementing the json.Marshaler interface.

However, when it is an anonymous struct field, it does get JSON-Marshalled as its original value.

package main

import (
    "encoding/json"
    "log"
    "time"
)

type TimeHolder struct {
    time.Time
}

type Post struct {
    Title string
    When  TimeHolder
}

func main() {
    p := Post{
        Title: "A test",
        When:  TimeHolder{time.Now()},
    }

    log.Printf("%+v\n", p)

    b, err := json.Marshal(p)
    if err != nil {
        log.Fatalln(err)
    }

    log.Printf("%+v\n", string(b))
}

Output:

2016/04/11 04:33:32 {Title:A test When:2016-04-11 04:33:32.088240358 -0500 CDT}
2016/04/11 04:33:32 {"Title":"A test","When":"2016-04-11T04:33:32.088240358-05:00"}

So maybe my case where TimeHolder is defined as type TimeHolder timeTime is not really a problem. The behavior as an anonymous struct field, however, doesn't line up with Go's JSON encoding.

Thanks, Eddy

[ereyes01]

You may wonder why I'm playing with such strange corner cases :-) I was trying to get this to work with gorethink: https://github.com/ereyes01/servertime

I may rethink my approach to this if the fix isn't easy (no pun intended).

Thanks, Eddy

[dancannon]

Before you start rethinking everything (pun intended :D) let me have a look at the code this evening to see if I can figure out solution.

[ereyes01]

I think this problem applies more generally to all embedded anonymous struct fields, not just those of type time.Time. Observe the following extended example:

package main

import (
    "log"
    "time"

    r "github.com/dancannon/gorethink"
)

type TimeHolder struct {
    time.Time
}

type ANumber struct {
    int
}

type Post struct {
    Title string
    When  TimeHolder
    Value ANumber
}

func main() {
    p := Post{
        Title: "A test",
        When:  TimeHolder{time.Now()},
        Value: ANumber{100},
    }

    log.Printf("%+v\n", p)

    session, err := r.Connect(r.ConnectOpts{
        Address:  "localhost:28015",
        Database: "test",
    })
    if err != nil {
        log.Fatal(err)
    }

    if _, err := r.DB("test").Table("time_test").Delete().RunWrite(session); err != nil {
        log.Fatal(err)
    }

    response, err := r.DB("test").Table("time_test").Insert(p).RunWrite(session)
    if err != nil {
        log.Fatal(err)
    }

    log.Printf("%+v\n", response)

    cursor, err := r.DB("test").Table("time_test").Run(session)
    if err != nil {
        log.Fatal(err)
    }

    if err := cursor.One(&p); err != nil {
        log.Fatal(err)
    }

    log.Printf("%+v\n", p)
}

Output:

2016/04/11 14:15:47 {Title:A test When:2016-04-11 14:15:47.178705733 -0500 CDT Value:{int:100}}
2016/04/11 14:15:47 {Errors:0 Inserted:1 Updated:0 Unchanged:0 Replaced:0 Renamed:0 Skipped:0 Deleted:0 Created:0 DBsCreated:0 TablesCreated:0 Dropped:0 DBsDropped:0 TablesDropped:0 GeneratedKeys:[67afca66-f146-4f44-bca2-ef4011965676] FirstError: ConfigChanges:[] Changes:[]}
2016/04/11 14:15:47 {Title:A test When:0001-01-01 00:00:00 +0000 UTC Value:{int:0}}

In this case, Post.Value was initialized to ANumber{100} but was inserted into the DB as a zero value. I tried adding other named fields to the ANumber struct, and the named fields get written into the DB correctly. However, the anonymous embedded struct field is always zeroed out.

thanks, Eddy

[dancannon]

Unfortunately I dont have the time to look at this issue right now (sorry!) Would it be possible if you could investigate the issue?