Ruby and SnakeYAML

Recently I have seen a post yaml in Java and Ruby where SnakeYAML was not chosen as the YAML parser.
The message is:
Because snakeyaml seems to have a syntactical problem with this YAML document we did no further investigations on snakeyaml.

But the real problem is that the document contains tags and the parser must be instructed how to process them.
Let us see what we can do.
The document:

--- !ruby/object:Test::Module::Object
sub1: !ruby/object:Test::Module::Sub1
  att1: []
  att2: 0
  att3: []
sub2: !ruby/object:Test::Module::Sub2
  att1: MyString
  att2:
  - entry1
  att3: 12345

We do not need a lot of code to parse the document:

Constructor con = new Constructor(TestObject.class);
con.addTypeDescription(new TypeDescription(TestObject.class, "!ruby/object:Test::Module::Object"));
con.addTypeDescription(new TypeDescription(Sub1.class, "!ruby/object:Test::Module::Sub1"));
con.addTypeDescription(new TypeDescription(Sub2.class, "!ruby/object:Test::Module::Sub2"));
Yaml yaml = new Yaml(new Loader(con));
return (TestObject) yaml.load(input);

Let's create a YAML document:

DumperOptions options = new DumperOptions();
options.setExplicitStart(true);
options.setExplicitRoot(Tags.MAP);
Yaml yaml2 = new Yaml(options);
String output = yaml2.dump(result);

This is the result:

---
sub1:
  att1: []
  att2: 0
  att3: []
sub2:
  att1: MyString
  att2: [entry1]
  att3: 12345

As you can see no tags are used. Normally SnakeYAML tries to avoid emitting tags as much as possible to simplify inter-language communication. But it seems that dynamically typed languages do not have any other means to define a class of an instance as to use a tag.
Let's emit the tags:

DumperOptions options = new DumperOptions();
options.setExplicitStart(true);
Representer repr = new Representer();
repr.addClassTag(TestObject.class, "!ruby/object:Test::Module::Object");
repr.addClassTag(Sub1.class, "!ruby/object:Test::Module::Sub1");
repr.addClassTag(Sub2.class, "!ruby/object:Test::Module::Sub2");
Yaml yaml2 = new Yaml(new Dumper(repr, options));
String output = yaml2.dump(result);

The document with tags:

--- !ruby/object:Test::Module::Object
sub1: !ruby/object:Test::Module::Sub1
  att1: []
  att2: 0
  att3: []
sub2: !ruby/object:Test::Module::Sub2
  att1: MyString
  att2: [entry1]
  att3: 12345

This document should be properly consumed by the Ruby parser. Unfortunately it requires to use the latest source from Mercurial. Current version (1.5) does not emit the tag for JavaBean properties even when the tag is explicitly defined. Either wait for the release after 1.5 or take the source !
SnakeYAML can work with YAML documents coming from Ruby parser.

Mission Accomplished.