Format XML split attributes with closing tag on new line

[ecool]

When working in vscode, I like to use the Alt+Up and Alt+Down keybinding for moving stuff around, and allowing for the ending of the tag to be on a new line if the attributes are aligned would be very helpful.

current:

<tag
    attr1=""
    attr2="" />

<tag
    attr1=""
    attr2="" >

proposed:

<tag
    attr1=""
    attr2=""
/>

<tag
    attr1=""
    attr2=""
>

proposed setting:
xml.format.splitAttributesCloseNewLine = true - only use if xml.format.splitAttributes = true.

[angelozerr]

@fbricon what do you think about this format settings?

@datho7561 do you think it can be easy to implement it?

[datho7561]

Its not trivial to implement, since you need to take into account > and />, but it looks fairly straightforward.

[datho7561]

Also, we would need to decide how formatting with just one attribute is handled

[ecool]

@datho7561 it looks like the current setting for splitAttributes keeps a single attribute on the line with the tag.

<tag attr1="" />

So, current behavior seems to be only split when more than 1 attribute. Not sure if there should be another setting for a single attribute decision but it does counteract the main reason I was looking into having the ending of the tag be on a new line. (The easy movement/duplication of attribute lines with vscode shortcuts)

If following the understanding of making it easier to manage attributes with the shortcuts (including all line operations), I believe there should be a way to have a single attribute being split to a separate line as well.

[thet]

Format suggestion: Indent the closing part the same level the attributes are indented:

<tag
    attr1=""
    attr2=""
    />

<tag
    attr1=""
    attr2=""
    >

This follows the Zope's toolkit ZCML style guide: https://zopetoolkit.readthedocs.io/en/latest/codingstyle/zcml-style.html#opening-tags
And it looks a bit nicer, IMO.

[AlexXuChen]

I'm interested in taking this issue.

[angelozerr]

Before working on this issue, perhaps we should rewrite the XML formatter (see PR eclipse-lemminx/lemminx#1044)

@datho7561 what do you think about that?

[datho7561]

I think the formatter rewrite will take a while. In the mean time, it would be neat to support this feature. It shouldn't require many changes to the existing formatter to implement this feature.