Liquid tag to render `app/view/` erb partials in `cdk/product_templates/*/*/templates/` liquid templates

render_erb.rb

module CDK
  class RenderERB < Liquid::Tag
    SYNTAX = /(?<path>#{Liquid::QuotedFragment})(?<locals>\s+.*)?/
    private_constant :SYNTAX

    def initialize(tag_name, markup, tokens)
      super

      @data = SYNTAX.match(markup).named_captures
    end

    def render(context)
      ERBRenderer.new(context, @data).render
    end

    class ERBRenderer
      ASSIGNMENT = /(\w+):(#{Liquid::QuotedFragment})/
      private_constant :ASSIGNMENT

      def initialize(context, data)
        @context = context
        @data = data
      end

      def render
        partial_renderer.render(partial: partial_path, locals: locals)
      end

    private

      def partial_renderer
        @partial_renderer ||= @context.registers[:action_view]
      end

      def partial_path
        path = @data["path"] || ""
        path.delete("\"")
      end

      def locals
        @data["locals"].scan(ASSIGNMENT).each_with_object({}) do |(key, value), previous|
          previous[key.to_sym] = get_variable_from_context_or_view(value)
        end
      end

      def get_variable_from_context_or_view(lookup_key)
        @context[lookup_key]
      rescue NoMethodError
        get_variable_from_view(lookup_key)
      end

      def get_variable_from_view(name)
        return unless partial_renderer.instance_variable_defined?(:"@#{name}")

        partial_renderer.instance_variable_get(:"@#{name}")
      end
    end
  end
end