resolves #59 track header attributes in source document

CHANGELOG.adoc

@@ -4,6 +4,12 @@
 This document provides a curated view of the changes to Asciidoctor Reducer in each release.
 For a detailed view of what has changed, refer to the {url-repo}/commits/main[commit history] on GitHub.
 
+== Unreleased
+
+=== Added
+
+* Track header attributes in source document and assign to `source_header_attributes` attr reader on Document instance (#59)
+
 == 1.0.6 (2024-02-12) - @mojavelinux
 
 === Fixed

lib/asciidoctor/reducer/extensions.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require 'asciidoctor' unless defined? Asciidoctor.load
+require_relative 'header_attribute_tracker'
 require_relative 'preprocessor'
 require_relative 'tree_processor'
 
@@ -10,6 +11,7 @@ module Extensions
 
     def group
       proc do
+        document.extend HeaderAttributeTracker
         next if document.options[:reduced] # group invoked again if includes are found and sourcemap option is true
         preprocessor Preprocessor
         tree_processor TreeProcessor

lib/asciidoctor/reducer/header_attribute_tracker.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+module Asciidoctor::Reducer
+  module HeaderAttributeTracker
+    def self.extended instance
+      instance.singleton_class.send :attr_reader, :source_header_attributes
+    end
+
+    def finalize_header(*) # rubocop:disable Style/MethodDefParentheses
+      @source_header_attributes = @attributes_modified.each_with_object({}) do |name, accum|
+        accum[name] = @attributes[name]
+      end
+      super
+    end
+  end
+end

spec/extensions_spec.rb

@@ -7,6 +7,7 @@
       (expect group).to be_a Proc
       doc = Asciidoctor.load []
       reg = (Asciidoctor::Extensions.create described_class.key, &group).activate doc
+      (expect doc.singleton_class.ancestors.map(&:name)).to include 'Asciidoctor::Reducer::HeaderAttributeTracker'
       (expect reg.preprocessors).to have_size 1
       (expect reg.tree_processors).to have_size 1
     end

spec/reducer_spec.rb

@@ -1,6 +1,10 @@
 # frozen_string_literal: true
 
 describe Asciidoctor::Reducer do
+  let :empty_hash do
+    {}
+  end
+
   it 'should be able to require library from Ruby process' do
     # NOTE asciidoctor/reducer/version will already be required by Bundler
     script_file = fixture_file 'print_version.rb'
@@ -43,6 +47,7 @@
         (expect doc.attr 'docname').to eql (input_file_basename '.adoc')
         (expect doc.attr 'docfile').to eql input_file
         (expect doc.attr 'docdir').to eql (File.dirname input_file)
+        (expect doc.source_header_attributes).to eql empty_hash
       end)
     end
   end
@@ -61,6 +66,7 @@
         (expect doc.options[:reduced]).to be_falsy
         (expect doc.sourcemap).to be_falsy
         (expect doc.blocks[0].source_location).to be_nil
+        (expect doc.source_header_attributes).to eql empty_hash
       end)
     end
   end
@@ -1704,6 +1710,7 @@
         (expect (doc.attr? 'sectnums')).to be true
         (expect (doc.attr? 'icons', 'font')).to be true
         (expect (doc.attr? 'toc')).to be true
+        (expect doc.source_header_attributes).to eql 'sectnums' => '', 'icons' => 'font', 'toc' => ''
       end)
     end
   end
@@ -1811,13 +1818,15 @@
     run_scenario do
       input_source <<~'END'
       = Book Title
+      :chaptersdir: ignored
 
       include::{chaptersdir}/ch1.adoc[]
       END
 
       reduce_options attributes: 'chaptersdir=chapters', sourcemap: true
       expected_source <<~'END'
       = Book Title
+      :chaptersdir: ignored
 
       == Chapter One
 
@@ -1828,7 +1837,9 @@
         delegate.call doc
         blocks = doc.find_by {|it| it.context != :document }
         (expect blocks).to have_size 3
-        (expect (blocks.map {|it| it.lineno })).to eql [1, 3, 5]
+        (expect (blocks.map {|it| it.lineno })).to eql [1, 4, 6]
+        # the hash is empty since the attribute is hard set by the API
+        (expect doc.source_header_attributes).to eql empty_hash
       end)
     end
   end