Preserve attribute line breaks

[xorye]

Signed-off-by: David Kwon [email protected]

[xorye]

This PR is ready for review.

Instead of introducing a formatting setting that keeps all newlines from non-empty lines, this PR introduces a new formatting setting, (ie, in VS Code: xml.format.preserveAttributeLineBreaks) that selectively keeps newlines from non-empty lines that come before and after element attributes.

For example:

<a \nattribute=\n"value"\n/>
    ^           ^        ^
    1           2        3

The formatter will keep 1 because it comes before an attribute.
The formatter will lose 2 because it exists inside an attribute.
The formatter will keep 3 because it comes after an attribute. (Note: formatting will only keep 3 if the element a has a self-closing tag. In this case, a it is a self-closing tag.)

These characteristics are useful in these cases:

End tag closing bracket is in a new line

<a attr="value"></a
>

formats to

<a attr="value"></a>

Attribute name/delimiter/value on separate lines

<a attr
=
"value"></a>

formats to

<a attr="value"></a>

As a plus, this setting will not will not keep newlines inside of the XML declaration (<?xml version="1.0" encoding="UTF-8"?>).

To review this PR with VS Code, please also check out redhat-developer/vscode-xml#271, which adds the xml.format.preserveAttributeLineBreaks setting:

Demo:

<?xml version="1.0" encoding="UTF-8"?>
<a>
    <li attribute="123456789" attribute="123456789" attribute="123456789"
        attribute="123456789" attribute="123456789" attribute="123456789"
        attribute="123456789" attribute="123456789" attribute="123456789"
        attribute="123456789" attribute="123456789" attribute="123456789"
    />
</a>

[xorye]

The gif is a bit misleading since the attribute names are all aligned since the tab size is 4 spaces.

This PR will indent the attribute names depending on the element's indentation and will not align attribute names for the moment. I created a new issue for attribute aligning here: #272

[fbricon]

The closing bracket is moved to the previous line, it wasn't supposed to happen

[datho7561]

The process looks pretty similar for one attribute and many attributes. Is it possible to avoid checking if there is one attribute, and use a general process that works for any number?

[xorye]

fixed