Remove all empty elements but classed spans using HTML Purifier

Question

I'm trying to remove every empty element in an input using HTML Purifier, but I want to keep the spans that meet a list of classes. So, for instance:

<div>&nbsp;</div><span class="color-gray"></span><div></div>

Should become:

<span class="color-gray"></span>

The configuration I'm using is:

'AutoFormat.RemoveEmpty.RemoveNbsp' => true,
'AutoFormat.RemoveEmpty' => true,
'CSS.AllowedProperties' => array(),
'Core.RemoveProcessingInstructions' => true,
'HTML.Allowed' => 'a[href|target],h1,h2,p,strong,em,b,i,ul,ol,li,span[class]'

But, as you may imagine, it is not what I expected, as it removes <span>, too. Do you have any idea on how to solve it?

Answer 1

Mm, you won't be able to do this directly, however, it should be a simple patch to RemoveEmpty; just add an extra check for an attribute at the beginning of handleElement.