https://sources.debian.org/patches/asciidoctor/2.0.18-2/0001-Port-tests-to-haml-6.patch/ (backport)
https://github.com/asciidoctor/asciidoctor/pull/4395

From 25ee484dd66cc813eaa421d1c104ae64478e51ff Mon Sep 17 00:00:00 2001
From: Antonio Terceiro <terceiro@debian.org>
Date: Mon, 26 Dec 2022 13:11:36 -0300
Subject: [PATCH] Port tests to haml 6

Forwarded: https://github.com/asciidoctor/asciidoctor/pull/4395
Fixes: #4382
--- a/asciidoctor.gemspec
+++ b/asciidoctor.gemspec
@@ -38,7 +38,7 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'cucumber', '~> 3.1.0'
   # erubi is needed for testing alternate eRuby impls
   s.add_development_dependency 'erubi', '~> 1.10.0'
-  s.add_development_dependency 'haml', '~> 5.2.0'
+  s.add_development_dependency 'haml', '~> 6.1'
   s.add_development_dependency 'minitest', '~> 5.14.0'
   s.add_development_dependency 'nokogiri', '~> 1.10.0'
   s.add_development_dependency 'rake', '~> 12.3.0'
--- a/lib/asciidoctor/converter/template.rb
+++ b/lib/asciidoctor/converter/template.rb
@@ -29,7 +29,7 @@ class Converter::TemplateConverter < Con
     erb: { trim: 0 },
     # TODO line 466 of haml/compiler.rb sorts the attributes; file an issue to make this configurable
     # NOTE AsciiDoc syntax expects HTML/XML output to use double quotes around attribute values
-    haml: { format: :xhtml, attr_wrapper: '"', escape_attrs: false, ugly: true },
+    haml: { format: :xhtml, attr_quote: '"', escape_attrs: false, ugly: true },
     slim: { disable_escape: true, sort_attrs: false, pretty: false },
   }
 
--- a/test/converter_test.rb
+++ b/test/converter_test.rb
@@ -9,7 +9,7 @@ context 'Converter' do
       assert_kind_of Asciidoctor::Converter::CompositeConverter, doc.converter
       selected = doc.converter.find_converter('paragraph')
       assert_kind_of Asciidoctor::Converter::TemplateConverter, selected
-      assert_kind_of Tilt::HamlTemplate, selected.templates['paragraph']
+      assert_kind_of Haml::Template, selected.templates['paragraph']
       assert_equal :html5, selected.templates['paragraph'].options[:format]
     end
 
@@ -18,7 +18,7 @@ context 'Converter' do
       assert_kind_of Asciidoctor::Converter::CompositeConverter, doc.converter
       selected = doc.converter.find_converter('paragraph')
       assert_kind_of Asciidoctor::Converter::TemplateConverter, selected
-      assert_kind_of Tilt::HamlTemplate, selected.templates['paragraph']
+      assert_kind_of Haml::Template, selected.templates['paragraph']
       assert_equal :xhtml, selected.templates['paragraph'].options[:format]
     end
 
@@ -95,7 +95,7 @@ context 'Converter' do
       %w(paragraph sidebar).each do |node_name|
         selected = doc.converter.find_converter node_name
         assert_kind_of Asciidoctor::Converter::TemplateConverter, selected
-        assert_kind_of Tilt::HamlTemplate, selected.templates[node_name]
+        assert_kind_of Haml::Template, selected.templates[node_name]
         assert_equal %(block_#{node_name}.html.haml), File.basename(selected.templates[node_name].file)
       end
     end
@@ -126,7 +126,7 @@ context 'Converter' do
       %w(paragraph).each do |node_name|
         selected = doc.converter.find_converter node_name
         assert_kind_of Asciidoctor::Converter::TemplateConverter, selected
-        assert_kind_of Tilt::HamlTemplate, selected.templates[node_name]
+        assert_kind_of Haml::Template, selected.templates[node_name]
         assert_equal %(block_#{node_name}.xml.haml), File.basename(selected.templates[node_name].file)
       end
     end
@@ -215,7 +215,7 @@ context 'Converter' do
       refute_empty caches[:templates]
       paragraph_template = caches[:templates].values.find {|t| File.basename(t.file) == 'block_paragraph.html.haml' }
       refute_nil paragraph_template
-      assert_kind_of ::Tilt::HamlTemplate, paragraph_template
+      assert_kind_of Haml::Template, paragraph_template
     end
 
     test 'should be able to disable template cache' do
--- a/test/fixtures/custom-backends/haml/docbook5/block_paragraph.xml.haml
+++ b/test/fixtures/custom-backends/haml/docbook5/block_paragraph.xml.haml
@@ -1,6 +1,6 @@
 - if title?
   %formalpara{'xml:id'=>@id, role: (attr :role), xreflabel: (attr :reftext)}
-    %title=title
-    %para=content
+    %title!=title
+    %para!=content
 - else
-  %para{'xml:id'=>@id, role: (attr :role), xreflabel: (attr :reftext)}=content
+  %para{'xml:id'=>@id, role: (attr :role), xreflabel: (attr :reftext)}!=content
--- a/test/fixtures/custom-backends/haml/html5-tweaks/block_paragraph.html.haml
+++ b/test/fixtures/custom-backends/haml/html5-tweaks/block_paragraph.html.haml
@@ -1 +1 @@
-%p=content
+%p!=content
--- a/test/fixtures/custom-backends/haml/html5-tweaks/embedded.html.haml
+++ b/test/fixtures/custom-backends/haml/html5-tweaks/embedded.html.haml
@@ -1 +1 @@
-=content
+!=content
--- a/test/fixtures/custom-backends/haml/html5/block_paragraph.html.haml
+++ b/test/fixtures/custom-backends/haml/html5/block_paragraph.html.haml
@@ -1,3 +1,3 @@
 - if title?
-  .title=title
-%p{id: @id, class: (attr 'role')}=content
+  .title!=title
+%p{id: @id, class: (attr 'role')}!=content
--- a/test/fixtures/custom-backends/haml/html5/block_sidebar.html.haml
+++ b/test/fixtures/custom-backends/haml/html5/block_sidebar.html.haml
@@ -1,5 +1,5 @@
 %aside{id: @id, class: (attr 'role')}
   - if title?
     %header
-      %h1=title
-  =content.chomp
+      %h1!=title
+  !=content.chomp
--- a/test/invoker_test.rb
+++ b/test/invoker_test.rb
@@ -616,7 +616,7 @@ context 'Invoker' do
     assert_kind_of Asciidoctor::Converter::CompositeConverter, doc.converter
     selected = doc.converter.find_converter 'paragraph'
     assert_kind_of Asciidoctor::Converter::TemplateConverter, selected
-    assert_kind_of Tilt::HamlTemplate, selected.templates['paragraph']
+    assert_kind_of Haml::Template, selected.templates['paragraph']
   end
 
   test 'should load custom templates from multiple template directories' do