How to compact existing XML using Nokogiri - ruby

Question

I'm trying to compact an existing XML file using Nokogiri. I have the following demo code:
#!/usr/bin/env ruby
require 'nokogiri'
doc = Nokogiri.XML <<-XML.strip
<?xml version="1.0" encoding="UTF-8"?>
<root>
<foo>
<bar>test</bar>
</foo>
</root>
XML
doc.write_xml_to($stdout, indent: 0)
I expected to see:
<?xml version="1.0" encoding="UTF-8"?>
<root><foo><bar>test</bar></foo></root>
but instead I saw:
<?xml version="1.0" encoding="UTF-8"?>
<root>
<foo>
<bar>test</bar>
</foo>
</root>
I tried:
doc.write_to($stdout, indent: 0, save_with: Nokogiri::XML::Node::SaveOptions::AS_XML)
but that doesn't work either.
How can I remove the ignorable whitespaces?

Answer 1

You can tell Nokogiri to ignore empty text nodes and then to output without indentation:
require 'nokogiri'
xml = <<EOT
<?xml version="1.0" encoding="UTF-8"?>
<root>
<foo>
<bar>test</bar>
</foo>
</root>
EOT
doc = Nokogiri::XML(xml) { |opts|
opts.noblanks
opts.strict.noblanks
}
doc.to_xml(:indent_text => '', :indent => 0)
# => "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" +
# "<root>\n" +
# "<foo>\n" +
# "<bar>test</bar>\n" +
# "</foo>\n" +
# "</root>\n"

Answer 2

Okay, I answer my own question.
Nokogiri does not remove the white spaces because Nokogiri doesn't know if the white spaces are ignorable or not (no DTD, no schema), so it keeps all the whitespace-only text as text nodes. I should remove them manually before writing the XML doc to the IO device.
#!/usr/bin/env ruby
require 'bundler'
Bundler.require :default
doc = Nokogiri.XML <<-XML.strip
<?xml version="1.0" encoding="UTF-8"?>
<root>
<foo>
<bar>test</bar>
</foo>
</root>
XML
# remove ignorable white spaces
doc.xpath('//text()').each do |node|
node.content = '' if node.text =~ /\A\s+\z/m
end
doc.write_xml_to($stdout, indent: 0)
This is a big progress for me, but I still haven't reached my goal because the XML file I'm working on has inline self-closing tags, and there are whitespace-only text nodes between those tags that should not be compacted. I'm trying to figure out a way to handle this corner case now.