nokogiri Jruby does not let you move nodes from one document to another, MRI does

[jrochkind]

MRI nokogiri version

$ nokogiri -v
# Nokogiri (1.8.3)
    ---
    warnings: []
    nokogiri: 1.8.3
    ruby:
      version: 2.5.1
      platform: x86_64-darwin16
      description: ruby 2.5.1p57 (2018-03-29 revision 63029) [x86_64-darwin16]
      engine: ruby
    libxml:
      binding: extension
      source: packaged
      libxml2_path: "/Users/jrochkind/.gem/ruby/2.5.1/gems/nokogiri-1.8.3/ports/x86_64-apple-darwin16.7.0/libxml2/2.9.8"
      libxslt_path: "/Users/jrochkind/.gem/ruby/2.5.1/gems/nokogiri-1.8.3/ports/x86_64-apple-darwin16.7.0/libxslt/1.1.32"
      libxml2_patches:
      - 0001-Revert-Do-not-URI-escape-in-server-side-includes.patch
      libxslt_patches: []
      compiled: 2.9.8
      loaded: 2.9.8

Jruby nokogiri version

$ nokogiri -v
Ignoring jruby-launcher-1.1.5-java because its extensions are not built. Try: gem pristine jruby-launcher --version 1.1.5
# Nokogiri (1.8.3)
    ---
    warnings: []
    nokogiri: 1.8.3
    ruby:
      version: 2.5.0
      platform: java
      description: jruby 9.2.0.0 (2.5.0) 2018-05-24 81156a8 Java HotSpot(TM) 64-Bit Server
        VM 25.121-b13 on 1.8.0_121-b13 +jit [darwin-x86_64]
      engine: jruby
      jruby: 9.2.0.0
    xerces: Xerces-J 2.11.0
    nekohtml: NekoHTML 1.9.21

Reproduction:

require 'nokogiri'

xml_src = "<record><field><value>3</value></field></record>"

doc1 = Nokogiri::XML.parse(xml_src)

doc2 = Nokogiri::XML::Document.new

node = doc1.at_xpath("//field")
node.remove

doc2.add_child(node)

puts "===="
puts doc2.to_xml

In MRI nokogiri, this works fine, and prints what you'd expect:

<?xml version="1.0"?>
<field>
  <value>3</value>
</field>

In JRuby nokogiri, it raises:

RuntimeError: org.w3c.dom.DOMException: WRONG_DOCUMENT_ERR: A node is used in a different document than the one that created it.
                     add_child_node at nokogiri/XmlNode.java:1701
  add_child_node_and_reparent_attrs at /Users/jrochkind/.gem/jruby/2.5.0/gems/nokogiri-1.8.3-java/lib/nokogiri/xml/node.rb:882
                          add_child at /Users/jrochkind/.gem/jruby/2.5.0/gems/nokogiri-1.8.3-java/lib/nokogiri/xml/node.rb:142
                          add_child at /Users/jrochkind/.gem/jruby/2.5.0/gems/nokogiri-1.8.3-java/lib/nokogiri/xml/document.rb:249
                             <main> at test_ns.rb:12

Surprisingly, doc2.root = node does seem to work without raising, JRuby nokogiri can move a node from one doc to another using root=, at least.

[jrochkind]

(oops, doc2.root = node does sort of work, but if there are namespaces involved it doesn't do the same thing with them as in MRI nokogiri, where I consider MRI's behavior correct. But namespace stuff has a variety of other inconsistencies between MRI and JRuby nokogiri, and is so confusing, that other than mentioning it's a thing, I won't go into details in this issue).

[flavorjones]

I'll take a look -- we've got pretty thorough tests for reparenting nodes, but it's totally possible we've missed an edge case that affects JRuby.

[jrochkind]

Cool, thanks, the repro is above which you can make into a test if you like. If somehow you can't repro with that script that raises for me... that'd be odd.

[jvshahid]

pushed a fix in #1777. @flavorjones can you take a look at the PR.