Implement nodelist in the Doc tag so it may be visited

test/unit/tags/doc_tag_unit_test.rb

@@ -157,4 +157,28 @@ class DocTagUnitTest < Minitest::Test
     assert_template_result('', "{% doc %}123{% enddoc\nxyz %}")
     assert_template_result('', "{% doc %}123{% enddoc\n   xyz  enddoc %}")
   end
+
+  def test_doc_tag_visitor
+    template_source = '{% doc %}{% enddoc %}'
+
+    assert_equal(
+      [Liquid::Doc],
+      visit(template_source),
+    )
+  end
+
+  private
+
+  def traversal(template)
+    ParseTreeVisitor
+      .for(Template.parse(template).root)
+      .add_callback_for(Liquid::Doc) do |tag|
+        tag_class = tag.class
+        tag_class
+      end
+  end
+
+  def visit(template)
+    traversal(template).visit.flatten.compact
+  end
 end