Error in mapping_rule.rb when running .to_xml with an element with same name in attribute and element

[kwkwan]

Refer to https://github.com/lutaml/xmi/blob/main/spec/fixtures/ISO%206709%20Edition%202.xml, some node like ownedComment may have annotatedElement as an attribute or as an element.

i.e.

test1 = <<~TEST1
<ownedComment>
  <annotatedElement xmi:idref="ABC"/>
</ownedComment>
TEST1

or

test2 = <<~TEST2
<ownedComment annotatedElement="test2">
</ownedComment>
TEST2

Suppose we have class definitions like:

require "nokogiri"
require "lutaml/model"
require "lutaml/model/xml_adapter/nokogiri_adapter"

Lutaml::Model::Config.configure do |config|
  config.xml_adapter = Lutaml::Model::XmlAdapter::NokogiriAdapter
end

class AnnotatedElement < Lutaml::Model::Serializable
  attribute :idref, :string

  xml do
    root "annotatedElement"
    map_attribute "idref", to: :idref, namespace: "http://www.omg.org/spec/XMI/20131001", prefix: "xmi"
  end
end

class OwnedComment < Lutaml::Model::Serializable
  attribute :annotated_attribute, :string
  attribute :annotated_element, AnnotatedElement

  xml do
    root "ownedComment"
    map_attribute "annotatedElement", to: :annotated_attribute
    map_element "annotatedElement", to: :annotated_element, prefix: nil, namespace: nil
  end
end

When we run OwnedComment.from_xml like:

t2 = OwnedComment.from_xml(test2)
t2.to_xml

Error will occur like the following output:

~/src/lutaml/lutaml-model/lib/lutaml/model/mapping_rule.rb:45:in `public_send': undefined method `idref' for "test2":String (NoMethodError)
                                     
          model.public_send(to)      
               ^^^^^^^^^^^^
	from ~/src/lutaml/lutaml-model/lib/lutaml/model/mapping_rule.rb:45:in `to_value_for'
	from ~/src/lutaml/lutaml-model/lib/lutaml/model/xml_adapter/xml_document.rb:347:in `block in build_attributes'
	from ~/src/lutaml/lutaml-model/lib/lutaml/model/xml_adapter/xml_document.rb:339:in `each'
	from ~/src/lutaml/lutaml-model/lib/lutaml/model/xml_adapter/xml_document.rb:339:in `each_with_object'
	from ~/src/lutaml/lutaml-model/lib/lutaml/model/xml_adapter/xml_document.rb:339:in `build_attributes'
	from ~/src/lutaml/lutaml-model/lib/lutaml/model/xml_adapter/xml_document.rb:189:in `build_unordered_element'
	from ~/src/lutaml/lutaml-model/lib/lutaml/model/xml_adapter/xml_document.rb:124:in `build_element'
	from ~/src/lutaml/lutaml-model/lib/lutaml/model/xml_adapter/xml_document.rb:53:in `handle_nested_elements'
	from ~/src/lutaml/lutaml-model/lib/lutaml/model/xml_adapter/xml_document.rb:149:in `add_to_xml'
	from ~/src/lutaml/lutaml-model/lib/lutaml/model/xml_adapter/xml_document.rb:225:in `block (2 levels) in build_unordered_element'
	from ~/src/lutaml/lutaml-model/lib/lutaml/model/xml_adapter/xml_document.rb:213:in `each'
	from ~/src/lutaml/lutaml-model/lib/lutaml/model/xml_adapter/xml_document.rb:213:in `block in build_unordered_element'
	from ~/src/lutaml/lutaml-model/lib/lutaml/model/xml_adapter/builder/nokogiri.rb:47:in `block in create_and_add_element'
	from ~/.rbenv/versions/3.1.5/lib/ruby/gems/3.1.0/gems/nokogiri-1.17.2-arm64-darwin/lib/nokogiri/xml/builder.rb:433:in `insert'
	from ~/.rbenv/versions/3.1.5/lib/ruby/gems/3.1.0/gems/nokogiri-1.17.2-arm64-darwin/lib/nokogiri/xml/builder.rb:415:in `method_missing'
	from ~/src/lutaml/lutaml-model/lib/lutaml/model/xml_adapter/builder/nokogiri.rb:87:in `public_send'
	... 32 levels...

It seems that the mapping_rule cannot distinguish annotatedElement whether it is an attribute or element and it try to output XML in wrong way.

[HassanAkbar]

@ronaldtse Currently, we are processing the input data into a hash. If an element and attribute have the same name, the element gets overridden.

Consider the following case:

<ownedComment xmlns:xmi="http://www.omg.org/spec/XMI/20131001" annotatedElement="test2">
  <annotatedElement xmi:idref="ABC"/>
</ownedComment>

Mapping Hash will be:

{ "annotatedElement"=>"test2" }

So, I am considering separating the elements and attributes in a nesting structure within the hash.

{
  "elements" => {
    "annotatedElement" => {
      "elements" => {}, "attributes" => {
        "http://www.omg.org/spec/XMI/20131001:idref" => "ABC"
      }
    },
  },
  "attributes" => {
    "annotatedElement" => "test2"
  }
}

NOTE: This approach might break existing custom methods.

Should we go with this approach? What do you suggest?

[kwkwan]

@ronaldtse Currently, we are processing the input data into a hash. If an element and attribute have the same name, the element gets overridden.

Consider the following case:

<ownedComment xmlns:xmi="http://www.omg.org/spec/XMI/20131001" annotatedElement="test2">
  <annotatedElement xmi:idref="ABC"/>
</ownedComment>

Mapping Hash will be:

{ "annotatedElement"=>"test2" }

So, I am considering separating the elements and attributes in a nesting structure within the hash.

{
  "elements" => {
    "annotatedElement" => {
      "elements" => {}, "attributes" => {
        "http://www.omg.org/spec/XMI/20131001:idref" => "ABC"
      }
    },
  },
  "attributes" => {
    "annotatedElement" => "test2"
  }
}

NOTE: This approach might break existing custom methods.

Should we go with this approach? What do you suggest?

Hi @ronaldtse, do you think we solve this issue by the quoted approach?

[ronaldtse]

@HassanAkbar I think XML attributes and XML elements should definitely be handled separately, so the proposed approach seems reasonable.

Re: this approach may break custom methods

• I don't think custom methods should touch the internal structures of the XML mappings.

We do have to remember that other key-value pair serialization methods do not distinguish "attribute" and "element" though.

P.S. This is a blocker for this task:

• Migrate this gem to use lutaml-model xmi#45

[ronaldtse]

Ping @kwkwan this issue is now fixed.