DEV: Filter topics by tag for categories (#17953)

* DEV: Filter topics by tag for categories and children

app/controllers/categories_controller.rb

@@ -30,7 +30,8 @@ class CategoriesController < ApplicationController
       is_homepage: current_homepage == "categories",
       parent_category_id: params[:parent_category_id],
       include_topics: include_topics(parent_category),
-      include_subcategories: include_subcategories
+      include_subcategories: include_subcategories,
+      tag: params[:tag]
     }
 
     @category_list = CategoryList.new(guardian, category_options)

app/models/category_list.rb

@@ -64,17 +64,18 @@ class CategoryList
 
     @all_topics = Topic.where(id: category_featured_topics.map(&:topic_id)).includes(:shared_draft, :category)
 
+    @all_topics = @all_topics.joins(:tags).where(tags: { name: @options[:tag] }) if @options[:tag].present?
+
     if @guardian.authenticated?
       @all_topics = @all_topics
         .joins("LEFT JOIN topic_users tu ON topics.id = tu.topic_id AND tu.user_id = #{@guardian.user.id.to_i}")
         .where('COALESCE(tu.notification_level,1) > :muted', muted: TopicUser.notification_levels[:muted])
     end
 
-    @all_topics = TopicQuery.remove_muted_tags(@all_topics, @guardian.user)
-    @all_topics = @all_topics.includes(:last_poster) if @options[:include_topics]
+    @all_topics = TopicQuery.remove_muted_tags(@all_topics, @guardian.user).includes(:last_poster)
     @all_topics.each do |t|
       # hint for the serializer
-      t.include_last_poster = true if @options[:include_topics]
+      t.include_last_poster = true
       t.dismissed = dismissed_topic?(t)
       @topics_by_id[t.id] = t
     end

spec/requests/categories_controller_spec.rb

@@ -139,6 +139,71 @@ RSpec.describe CategoriesController do
       expect(subsubcategory_response["topics"].map { |c| c['id'] }).to contain_exactly(topic3.id)
     end
 
+    describe 'topics filtered by tag for categories when requested' do
+      fab!(:tag) { Fabricate(:tag, name: "test-tag") }
+      fab!(:tag_2) { Fabricate(:tag, name: "second-test-tag") }
+      let(:topics_with_filter_tag) { [] }
+
+      before do
+        SiteSetting.max_category_nesting = 3
+      end
+
+      it 'includes filtered topics for categories' do
+        2.times do |i|
+          topics_with_filter_tag << Fabricate(:topic, category: category, tags: [tag])
+          Fabricate(:topic, category: category, tags: [tag_2])
+        end
+        CategoryFeaturedTopic.feature_topics
+
+        get "/categories.json?tag=#{tag.name}&include_topics=true"
+        expect(response.status).to eq(200)
+
+        category_list = response.parsed_body["category_list"]
+        category_response = category_list["categories"].find { |c| c["id"] == category.id }
+
+        expect(category_response["topics"].map { |c| c['id'] }).to contain_exactly(*topics_with_filter_tag.map(&:id))
+      end
+
+      it 'includes filtered topics for subcategories' do
+        subcategory = Fabricate(:category, user: admin, parent_category: category)
+
+        2.times do |i|
+          topics_with_filter_tag << Fabricate(:topic, category: subcategory, tags: [tag])
+          Fabricate(:topic, category: subcategory, tags: [tag_2])
+        end
+        CategoryFeaturedTopic.feature_topics
+
+        get "/categories.json?tag=#{tag.name}&include_subcategories=true&include_topics=true"
+        expect(response.status).to eq(200)
+
+        category_list = response.parsed_body["category_list"]
+        category_response = category_list["categories"].find { |c| c["id"] == category.id }
+        subcategory_response = category_response["subcategory_list"][0]
+
+        expect(subcategory_response["topics"].map { |c| c['id'] }).to contain_exactly(*topics_with_filter_tag.map(&:id))
+      end
+
+      it 'includes filtered topics for subsubcategories' do
+        subcategory = Fabricate(:category, user: admin, parent_category: category)
+        subsubcategory = Fabricate(:category, user: admin, parent_category: subcategory)
+
+        2.times do |i|
+          topics_with_filter_tag << Fabricate(:topic, category: subsubcategory, tags: [tag])
+          Fabricate(:topic, category: subsubcategory, tags: [tag_2])
+        end
+        CategoryFeaturedTopic.feature_topics
+
+        get "/categories.json?tag=#{tag.name}&include_subcategories=true&include_topics=true"
+        expect(response.status).to eq(200)
+
+        category_list = response.parsed_body["category_list"]
+        category_response = category_list["categories"].find { |c| c["id"] == category.id }
+        subsubcategory_response = category_response["subcategory_list"][0]["subcategory_list"][0]
+
+        expect(subsubcategory_response["topics"].map { |c| c['id'] }).to contain_exactly(*topics_with_filter_tag.map(&:id))
+      end
+    end
+
     describe 'categories and latest topics - ordered by created date' do
       fab!(:category) { Fabricate(:category) }
       fab!(:topic1) { Fabricate(:topic, category: category, created_at: 5.days.ago, updated_at: Time.now, bumped_at: Time.now) }