example_component.rb

# frozen_string_literal: true

class ExampleComponent < MiniView
  def template
    button type: "button", class: [
      "inline-flex items-center gap-x-1.5 rounded-md bg-indigo-600 px-3 py-2 text-sm font-semibold text-white shadow-sm",
      "hover:bg-indigo-500 focus-visible:outline focus-visible:outline-2 focus-visible:outline-offset-2 focus-visible:outline-indigo-600"
    ] do
      plain "This works"

      em do
        span "nesting"
        strong do
          plain "also works"
        end
      end
    end
  end
end

mini_view.rb

# frozen_string_literal: true

class MiniView
  undef :p

  def self.tag_elements
    @tag_elements ||= ActionView::Helpers::TagHelper::TagBuilder.instance_methods(false)
  end

  def template
    raise NotImplementedError
  end

  def render_in(view_context)
    raise ArgumentError, "#{self.class} does not support passing a block" if block_given?
    @view_context = view_context
    @view_context.with_output_buffer { template }
  end

  def plain(string)
    @view_context.concat(string)
  end

  def method_missing(method, ...)
    if self.class.tag_elements.include?(method)
      @view_context.concat @view_context.tag.__send__(method, ...)
    elsif @view_context.respond_to?(method, false)
      @view_context.__send__(method, ...)
    else
      super
    end
  end

  def respond_to_missing?(method, include_all = false)
    return true if super
    return true if self.class.tag_elements.include?(method)
    @view_context.respond_to?(method, false)
  end
end