require 'core/interactors/article_reader'

class ArticlesController < ApplicationController
  decorates_assigned :article, with: ContentItemDecorator

  def show
    @article = Core::ArticleReader.new(params[:id]).call do
      not_found
    end

    @breadcrumbs = BreadcrumbTrail.build(@article, category_tree)
  end
end

require 'core/interactors/article_reader'

class ArticlesController < ApplicationController
  decorates_assigned :article, with: ContentItemDecorator

  include Navigation

  def show
    @article = Core::ArticleReader.new(params[:id]).call do
      not_found
    end

    @breadcrumbs = BreadcrumbTrail.build(@article, category_tree)

    (@article.categories.map(&:id) + @article.parent_category_ids).each do |category|
      active_category category
    end
  end
end

Use Navigation concern to specify currently active categories
Use Navigation concern to specify currently active categories

The partial doesn't need to know about the current article now
