using XML::Builder to build a doc node

[stoivo]

Please describe the bug

I am working with xsd and I need to build a xml with the node "doc". Using the nokogiri builder I was expecting to use xml.doc() { ... } but it don't work. This uses method missing which has a name collision. I have added a demo script below. I couldn't find any solutions to this from the docs so I peeked into the source and make myself a little patch. I changed method missing to call add_node and added new public method add_node

    def method_missing(method, *args, &block) # :nodoc:
        if @context&.respond_to?(method)
          @context.send(method, *args, &block)
        else
          add_node(method.to_s.sub(/[_!]$/, ""), *args, &block)
        end
      end

      def add_node(name, *args, &block)
        node = @doc.create_element(name, *args) do |n|
          # Set up the namespace
          if @ns.is_a?(Nokogiri::XML::Namespace)
            n.namespace = @ns
            @ns = nil
          end
        end

        if @ns.is_a?(Hash)
          node.namespace = node.namespace_definitions.find { |x| x.prefix == @ns[:pending] }
          if node.namespace.nil?
            raise ArgumentError, "Namespace #{@ns[:pending]} has not been defined"
          end

          @ns = nil
        end

        insert(node, &block)
      end

If this is a patch you want included I would very much like to open the PR and contribute to nokogiri.

Help us reproduce what you're seeing

I did't write it as a test but I have a script to demo it.

# frozen_string_literal: true

require "nokogiri"

XSD = <<~XSD
<?xml version="1.0" encoding="UTF-8"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <xsd:element name="theDoc" type="Amount"/>
  <xsd:complexType name="Amount">
    <xsd:sequence>
      <xsd:element name="doc" type="xsd:string"/>
    </xsd:sequence>
  </xsd:complexType>
</xsd:schema>
XSD

class Scribe
  def self.write_xml(root)
    new.write_xml(root)
  end

  def write_xml(root)
    builder = Nokogiri::XML::Builder.new(encoding: "UTF-8") do |xml|
      build_xsd__root(xml, root)
    end
    builder.to_xml(save_with: Nokogiri::XML::Node::SaveOptions::DEFAULT_XML)
  end

  private

  attr_reader(:xml)

  def build_xsd__root(xml, root)
    # avoid passing the xml builder instance
    @xml = xml
    xml.theDoc() {
      build_amount(root[:theDoc])
    }

    @xml = nil
  end

  def build_xsd_string(str)
    xml.text(str)
  end

  def build_amount(value)
    node = xml.doc.create_element("doc")
    xml.add_node("doc") do
      build_xsd_string(value[:doc] + "new_code")
    end
    xml.doc() {
      build_xsd_string(value[:doc] + "old_code")
    }

    xml.add_node("doco") do
      build_xsd_string(value[:doc] + "new_code")
    end
    xml.doco() {
      build_xsd_string(value[:doc] + "old_code")
    }
  end
end

xml = <<~XML
  <?xml version="1.0" encoding="UTF-8"?>
  <theDoc>
    <doc>info</doc>
  </theDoc>
XML
doc = Nokogiri::XML(xml)
xsd = Nokogiri::XML::Schema(XSD)
pp({doc_errors: doc.errors, xsd_errors: xsd.validate(doc)})


root = {theDoc: {doc: "info"}}

scribed = Scribe.write_xml(root)

puts "====== scribed"
puts scribed
puts "====== xml"
puts xml


# > output
# {:doc_errors=>[], :xsd_errors=>[]}
# ====== scribed
# <?xml version="1.0" encoding="UTF-8"?>
# <theDoc>
#   <doc>infonew_code</doc>
#   <doco>infonew_code</doco>
#   <doco>infoold_code</doco>
# </theDoc>
# ====== xml
# <?xml version="1.0" encoding="UTF-8"?>
# <theDoc>
#   <doc>info</doc>
# </theDoc>
# [Finished in 1.4s]

If you haven't included a test, please provide whatever code you can, the inputs (if any), along with the output that you're seeing. We need to reproduce what you're seeing to be able to help!
-->

Expected behavior

Environment

[flavorjones]

Hi! Thanks for asking this question. Because it falls under user help, I've converted it to a discussion (hope that's OK).

The builder allows you to create nodes for names bound to pre-existing methods by appending an underscore (_). Docs explaining this are here.

Here's an example of what happens when you use doc versus doc_:

#!/usr/bin/env ruby

require "bundler/inline"

gemfile do
  source "https://rubygems.org"
  gem "nokogiri"
end

builder = Nokogiri::XML::Builder.new do |xml|
  xml.root {
    xml.doc {
      xml.thing "content"
    }
  }
end
builder.to_xml
# => "<?xml version=\"1.0\"?>\n" + "<root/>\n"

builder = Nokogiri::XML::Builder.new do |xml|
  xml.root {
    xml.doc_ {
      xml.thing "content"
    }
  }
end
builder.to_xml
# => "<?xml version=\"1.0\"?>\n" +
#    "<root>\n" +
#    "  <doc>\n" +
#    "    <thing>content</thing>\n" +
#    "  </doc>\n" +
#    "</root>\n"

I hope this is helpful?

[stoivo]

Thanks, this works.
Are you open for adding a method which taked the name as a string? I am generating this code from the xsds. Another option for me we to append _ to the end of all builder methods but it looks a but weird. I could also make a whitelist

[flavorjones]

@stoivo No, adding a new method to Builder is a breaking change. For example, if we add a method named node then anybody whose code is currently creating a tag named node would break.