allow None as an attribute value, for HTML boolean attributes #201
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
I was writing a script to convert some tags in Angular templates to a new API, and noticed that curiously lxml could parse and re-serialize boolean tags that have no value, but could not create new ones. It turns out libxml2 supports this by accepting NULL as the value for xmlSetNsProp(), creating an attribute node with NULL children instead of a text node.
This change allows None as a value for Element.set() so that those who value attributes with no value can create the same.
Note that lxml.etree.tostring() serializes these as
<form novalidate=''></form>
while lxml.html.tostring() produces the value in the test.