encoding/xml: support for XML namespace prefixes

[jordan2175]

Marshal-ing data back to XML does not seem to support namespace prefixes.. For example:

https://play.golang.org/p/6CY71H7mb4

The input XML is: <stix:STIX_Package>, but when it writes it back out it does <STIX_Package xmlns="stix">

Also, there does not appear to be any data elements like xml.Name for adding namespaces to a struct.... Something maybe like xml.NS????

[mikioh]

Dup of #6800

[jordan2175]

I think what I am looking for, as I do more research on it, is for xml.Marshal to support prefixes

[jordan2175]

Here is some more details about this issue: If you run this code:

https://play.golang.org/p/EucDh59yiB

package main

import (
    "encoding/xml"
    "fmt"
)

type HouseType struct {
    XMLName   xml.Name `xml:"prefix11 House"`
    MessageId string   `xml:"message_id,attr"`
}

func main() {

    var tm HouseType
    tm.MessageId = "test1234"

    var data1 []byte
    data1, _ = xml.MarshalIndent(tm, "", "    ")

    fmt.Println("Marshal")
    fmt.Println(string(data1))

    rawxml := `<prefix11:House message_id="1466" in_response_to="1"></prefix11:House>`

    var tm2 HouseType
    xml.Unmarshal([]byte(rawxml), &tm2)
    fmt.Println("\nUnmarshal")
    fmt.Println("Message ID", tm2.MessageId)
}

It will print out:

Marshal
<House xmlns="prefix11" message_id="test1234"></House>

Unmarshal
Message ID 1466

You will see that the marshal command does not make use of the prefix correctly. It should be prefix11:House. If I change the struct to look like the following then the marshal command will work but the unmarshal will not. NOTE the ":" in the XMLName field. So I can either marshal or unmarshal, but not both with prefixed XML

https://play.golang.org/p/44CMHXb3YM

type HouseType struct {
    XMLName   xml.Name `xml:"prefix11:House"`
    MessageId string   `xml:"message_id,attr"`
}

Making this change, changes the output to:

Marshal
<prefix11:House message_id="test1234"></prefix11:House>

Unmarshal
Message ID

[rsc]

See #11841.

[gopherbot]

CL https://golang.org/cl/12570 mentions this issue.

[rsc]

Blocked on #13400.

[rothskeller]

Just a note in support of this proposal: with encoding/xml as it stands, it is infeasible to interact with SOAP web services that use digitally signed requests. This is because XML digital signatures require the XML to be in canonical form, which requires a greater degree of control over namespaces than encoding/xml provides. Admittedly, calling a SOAP service from a Go program is kind of like towing a trailer behind your Ferrari, but sometimes interoperability with legacy systems is essential.

[vania-pooh]

Just a workaround while waiting for a fix:

type Data ...

type Root struct {
    XMLName  xml.Name  `xml:"prefix:root"`
    XmlNS    string    `xml:"xmlns:prefix,attr"`
    Data Data `xml:"data"`
}

root := Root {
    XmlNS: "urn:test.example.com",
    Data: ...,
}

b, err := xml.MarshalIndent(root, "", "    ")

This will produce the following:

<prefix:root xmlns:prefix="urn:test.example.com"/>
    <data>...</data>
</prefix:root>

[lordofscripts]

I am in awe that such a documented bug hinders such useful features has survived this long without fixing.

I hope somebody fixes this. For now, I found a replacement to encoding/xml using nbio/xml which handles namespaces properly.