It works almost like expected. The only problem is that empty tags have indentation whitespaces as content. I think deleting lines 171 and 192 in file lib/xml_builder.ex would fix it.

Also, the readme defines the dependency as {:xml_builder, "~> 3.1"} but it only works if it is defined as {:xml_builder_ex, "~> 3.1"}.

It’s not a problem, it is how it worked by design. There is an ability to provide a format: option to generate/2 and all the formatters would use it. Just gluing empty tags would violate this, so you always had an option to do format: [*: :indent, tag1: :none, tag2: :none].

But since it’s a common expectation to have empty tags glued, I added empty: :squeezed alongside empty: :full which does not respect the format setting and glues empty tags in (example from tests.)