Hello,

I attached a new patch that also avoid printing attributes without a
value (value is nil in the DOM).

I also refreshed the list of HTML boolean attributes from the current
standard, and put checking for a boolean attribute in a separate
inline function for clarity.

The patch also slightly improve the code by computing the indentation
column outside of loop and delegating indentation to `indent-line-to'.

Here is a change log:

2025-02-05  David Ponce  <da_vid@orange.fr>

	Fix DOM printing when an attribute value is not a string,
	which is often the case in SVG DOM.  Don't print attributes
	without a value.  Refresh the list of HTML boolean attributes.

	* dom.el (dom--html-boolean-attribute-p): New function.
	(dom-print): Use it.  Convert attribute value to string before
	to call `url-insert-entities-in-string'.  Don't print
	attribute without a value.  Compute indentation column outside
	of loop and call `indent-line-to' to indent line.

This new version passes the `dom-tests-print'.

Thanks!