Dasel don't preserve initial XML content.

[olblak]

Discussion?
While trying to use Dasel as a Go package in a personal project updatecli, I noticed that it drops XML comments, directives, and processes.

Describe the bug
Dasel don't preserve initial XML content.

To Reproduce
The command dasel -f example.xml -p xml

.example.xml

<?xml version="1.0" encoding="UTF-8"?>
<!-- This a commment -->
<name>
    <firstname tag="xx">John</firstname>
    <lastname>Doe</lastname>
</name>

.output

<name>
    <firstname tag="xx">John</firstname>
    <lastname>Doe</lastname>
</name>

.expectedOutput

<?xml version="1.0" encoding="UTF-8"?>
<!-- This a commment -->
<name>
    <firstname tag="xx">John</firstname>
    <lastname>Doe</lastname>
</name>

Another example is the command dasel put string -p xml -f example.xml .name.firstname Tom on the same example file, generated the following file:

<name>
  <firstname>Tom</firstname>
  <lastname>Doe</lastname>
</name>

Instead of:

.expectedOutput

<?xml version="1.0" encoding="UTF-8"?>
<!-- This a commment -->
<name>
    <firstname tag="xx">John</firstname>
    <lastname>Doe</lastname>
</name>

Expected behavior
I would expect Dasel to preserve all original XML instructions

Screenshots
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Desktop (please complete the following information):

• OS: Linux
• Version [1.21.2]

Additional context
After looking at Dasel and mxj code base, It appears that Dasel is manipulating a mxj.Map and could instead use the mxj.MapSeq which seems to preserve everything. I am still new to the two projects so I may need some guidance to contribute to this issue. It appears that some work is needed here but I may be missing something else.

[TomWright]

That file is indeed the one that needs editing.

I have done a quick test and found that simply using mxj.NewMapXmlSeq instead of mxj.NewMapXml doesn't work.

I'll have to do a bit more reading to find out how to correctly use mxj to solve this issue. Please bear with me!

[TomWright]

It seems that when using NewMapXmlSeq the XML version and comment information are added as map nodes at the root level causing confusion.

[olblak]

@TomWright Thanks for looking at this, I started looking at this comment clbanning/mxj#17 (comment) but unfortunately, I run out of time so I can't help as much as I would like to.