dom.SetNamespace creates `xmlns:` in child elements

[guitarpawat]

Describe the bug

In godoc of function dom.SetNamespace says that the XML namespace declaration will not be created if the namespace is already declared in a previous tree hierarchy. But currently, this function will create duplicate xmlns: in child elements

Please attach the output of go version

go version go1.22.4 linux/amd64

To Reproduce / Expected behavior Please attach a standalone Go test code that shows the problem, and what you expected to happen. The code:

package main

import (
    "fmt"
    "github.com/lestrrat-go/libxml2/dom"
)

func main() {
    root := dom.CreateDocument()
    doc, _ := root.CreateElement("Document")
    _ = doc.SetNamespace("https://example.com", "ex")
    _ = root.SetDocumentElement(doc)
    test, _ := root.CreateElement("Test")
    _ = test.SetNamespace("https://example.com", "ex")
    _ = doc.AddChild(test)
    test.SetNodeValue("test")
    fmt.Println(root.Dump(true))
}

Expected result:

<?xml version="1.0" encoding="utf-8"?>
<ex:Document xmlns:ex="https://example.com">
  <ex:Test>test</ex:Test>
</ex:Document>

Actual result:

<?xml version="1.0" encoding="utf-8"?>
<ex:Document xmlns:ex="https://example.com">
  <ex:Test xmlns:ex="https://example.com">test</ex:Test>
</ex:Document>

[lestrrat]

@guitarpawat Can you please check #103?

[guitarpawat]

@lestrrat Thanks for a quick response, it seems like your commit doesn't set parent element to the namespace

<?xml version="1.0" encoding="utf-8"?>
<Document>
  <ex:Test xmlns:ex="https://example.com">test</ex:Test>
</Document>

And it still have duplicate xmlns if we set the namespace for parent after child

func main() {
    root := dom.CreateDocument()
    doc, _ := root.CreateElement("Document")
    //_ = doc.SetNamespace("https://example.com", "ex") // delete
    _ = root.SetDocumentElement(doc)
    test, _ := root.CreateElement("Test")
    _ = test.SetNamespace("https://example.com", "ex")
    _ = doc.SetNamespace("https://example.com", "ex") // move to here
    _ = doc.AddChild(test)
    test.SetNodeValue("test")
    fmt.Println(root.Dump(true))
}

<ex:Document xmlns:ex="https://example.com">
  <ex:Test xmlns:ex="https://example.com">test</ex:Test>
</ex:Document>

[lestrrat]

@guitarpawat Oh, I found your problem. xmlSearchNs can only find duplicate namespaces if the node in question is already part of a document. You are setting the namespace and then adding the node, that's why it failed to find your namespace.

    t.Run("child ns after parent ns", func(t *testing.T) {
        root := CreateDocument()
        doc, _ := root.CreateElement("Document")
        _ = doc.SetNamespace("https://example.com", "ex")
        test, _ := root.CreateElement("Test")
        _ = doc.AddChild(test) // <---- THIS needs to go BEFORE SetNamespace
        _ = root.SetDocumentElement(doc)
        _ = test.SetNamespace("https://example.com", "ex")
        test.SetNodeValue("test")

        // root.Dump(true) should only contain one namespace declaration
        // for the 'ex' prefix
        dump := root.Dump(true)
        count := strings.Count(dump, `xmlns:ex="https://example.com"`)
        t.Logf("%s", dump)
        require.Equal(t, 1, count, "expected only one namespace declaration for 'ex' prefix")
    })

Also, it is NOT possible to find duplicates on children. So if you add a namespace on your child node and then add to a parent, that's not going to be fixed.

I added a minor fix to #103 including fixes to the test, and I believe it's working as intended now.

[guitarpawat]

Hi @lestrrat, I pulled your latest version from #103 (commit b1f63e9) and it is still not working for me

The xmlns is gone in child nodes but it also doesn't have a namespace prefix

package main

import (
    "fmt"
    "github.com/lestrrat-go/libxml2/dom"
)

func main() {
    root := dom.CreateDocument()
    doc, _ := root.CreateElement("Document")
    _ = root.SetDocumentElement(doc)
    _ = doc.SetNamespace("https://example.com", "ex")
    test, _ := root.CreateElement("Test")
    _ = doc.AddChild(test)
    _ = test.SetNamespace("https://example.com", "ex")
    test2, _ := root.CreateElement("Test2")
    _ = test.AddChild(test2)
    _ = test2.SetNamespace("https://example.com", "ex")

    fmt.Println(root.Dump(true))
}

<?xml version="1.0" encoding="utf-8"?>
<ex:Document xmlns:ex="https://example.com">
  <Test>
    <Test2/>
  </Test>
</ex: Document>

For clarification, I expect my message to look like this spec.

<ex:Document xmlns:ex="https://example.com">
  <ex:Test>
    <ex:Test2/>
  </ex:Test>
</ex:Document>

I managed to find a workaround by using CreateElementNS instead but it still has another issue with default namespace (will open another issue):

    root := dom.CreateDocument()
    doc, _ := root.CreateElementNS("https://example.com", "ex:Document")
    _ = root.SetDocumentElement(doc)
    test, _ := root.CreateElementNS("https://example.com", "ex:Test")
    _ = doc.AddChild(test)
    test2, _ := root.CreateElementNS("https://example.com", "ex:Test2")
    _ = test.AddChild(test2)

    fmt.Println(root.Dump(true))

[lestrrat]

Oh, oops?

~/dev/src/github.com/lestrrat-go/libxml2$ git push origin gh-102
To github.com:lestrrat-go/libxml2.git
 ! [rejected]        gh-102 -> gh-102 (fetch first)
error: failed to push some refs to 'github.com:lestrrat-go/libxml2.git'
hint: Updates were rejected because the remote contains work that you do
hint: not have locally. This is usually caused by another repository pushing
hint: to the same ref. You may want to first integrate the remote changes
hint: (e.g., 'git pull ...') before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.

How about now?

[guitarpawat]

@lestrrat I pulled commit 38fc65c32878 Child nodes still don't have prefix.

package main

import (
    "fmt"
    "github.com/lestrrat-go/libxml2/dom"
)

func main() {
    root := dom.CreateDocument()
    doc, _ := root.CreateElement("Document")
    _ = doc.SetNamespace("https://example.com", "ex")
    test, _ := root.CreateElement("Test")
    _ = doc.AddChild(test) // <---- THIS needs to go BEFORE SetNamespace
    _ = root.SetDocumentElement(doc)
    _ = test.SetNamespace("https://example.com", "ex")
    test.SetNodeValue("test")
    fmt.Println(root.Dump(true))
}

<?xml version="1.0" encoding="utf-8"?>
<ex:Document xmlns:ex="https://example.com">
  <Test>test</Test>                            <- this should be ex:Test
</ex:Document>

[lestrrat]

meh. Okay, I will be offline for a few days, so I'll work on it when I come back.

[guitarpawat]

Got it, thank you!

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