MarkdownTemplateHandler fixed for Rails 7.1

markdown_template_handler.rb

# config/initializers/markdown_template_handler.rb
module MarkdownTemplateHandler

  def self.call( template, source=nil )
    source ||= template.source
    
    # This worked prior to Rails 7.1:    
    # compiled_source = erb.call( template, source )
    
    # But with Rails 7.1 it threw "ActionView::Template::Error: wrong argument type ActionView::OutputBuffer (expected String)"
    # Because the '.to_s' had been removed in Rails 7.1 by this commit: https://github.com/rails/rails/commit/ee68644c284aa7512d06b4b5514b1236c1b63f55
    # So now you need to add it back to make it work with Redcarpet 3.6:
    compiled_source = ActionView::OutputBuffer.new( erb.call( template, source ) )
    compiled_source << '.to_s'
    
    "Redcarpet::Markdown.new(Redcarpet::Render::HTML.new).render(begin;#{compiled_source};end).html_safe"                   
  end
end