Add 'show' page for topic

Changelog: added

app/controllers/explore/projects_controller.rb

@@ -68,6 +68,15 @@ class Explore::ProjectsController < Explore::ApplicationController
   end
   # rubocop: enable CodeReuse/ActiveRecord
 
+  def topic
+    load_topic
+
+    return render_404 unless @topic
+
+    params[:topic] = @topic.name
+    @projects = load_projects
+  end
+
   private
 
   def load_project_counts
@@ -86,6 +95,10 @@ class Explore::ProjectsController < Explore::ApplicationController
     prepare_projects_for_rendering(projects)
   end
 
+  def load_topic
+    @topic = Projects::Topic.find_by_name(params[:topic_name])
+  end
+
   # rubocop: disable CodeReuse/ActiveRecord
   def preload_associations(projects)
     projects.includes(:route, :creator, :group, :project_feature, :topics, namespace: [:route, :owner])

app/views/explore/projects/topic.html.haml

+- @hide_top_links = false
+- @no_container = true
+- page_title    @topic.name, _("Topics")
+- max_topic_name_length = 50
+
+= render_dashboard_ultimate_trial(current_user)
+
+.gl-text-center.gl-bg-gray-10.gl-pb-2.gl-pt-6
+  .gl-pb-5.gl-align-items-center.gl-justify-content-center.gl-display-flex
+    .avatar-container.s60.gl-flex-shrink-0
+      = topic_icon(@topic, alt: _('Topic avatar'), class: 'avatar topic-avatar s60')
+    - if @topic.name.length > max_topic_name_length
+      %h1.gl-mt-3.str-truncated.has-tooltip{ title: @topic.name }
+        = truncate(@topic.name, length: max_topic_name_length)
+    - else
+      %h1.gl-mt-3
+        = @topic.name
+  - if @topic.description.present?
+    .topic-description.gl-ml-4.gl-mr-4
+      = markdown(@topic.description)
+
+%div{ class: container_class }
+  .gl-py-5.gl-border-gray-100.gl-border-b-solid.gl-border-b-1
+    %h3.gl-m-0= _('Projects with this topic')
+  .top-area.gl-pt-2.gl-pb-2
+    .nav-controls
+      = render 'shared/projects/search_form'
+      = render 'shared/projects/dropdown'
+      = render 'filter'
+
+  = render 'projects', projects: @projects

app/views/shared/projects/_topics.html.haml

@@ -8,7 +8,7 @@
       = sprite_icon('tag', css_class: 'icon gl-relative gl-mr-2')
 
       - project.topics_to_show.each do |topic|
-        - explore_project_topic_path = explore_projects_path(topic: topic)
+        - explore_project_topic_path = topic_explore_projects_path(topic_name: topic)
         - if topic.length > max_project_topic_length
           %a{ class: "#{ project_topics_classes } str-truncated-30 has-tooltip", data: { container: "body" }, title: topic, href: explore_project_topic_path, itemprop: 'keywords' }
             = truncate(topic, length: max_project_topic_length)
@@ -21,7 +21,7 @@
         - content = capture do
           %span.gl-display-inline-flex.gl-flex-wrap
             - project.topics_not_shown.each do |topic|
-              - explore_project_topic_path = explore_projects_path(topic: topic)
+              - explore_project_topic_path = topic_explore_projects_path(topic_name: topic)
               - if topic.length > max_project_topic_length
                 %a{ class: "#{ project_topics_classes } gl-mb-3 str-truncated has-tooltip", data: { container: "body" }, title: topic, href: explore_project_topic_path, itemprop: 'keywords' }
                   = truncate(topic, length: max_project_topic_length)

config/routes/explore.rb

@@ -5,6 +5,7 @@ namespace :explore do
     collection do
       get :trending
       get :starred
+      get 'topics/:topic_name', action: :topic, as: :topic, constraints: { topic_name: /.+/ }
     end
   end
 

locale/gitlab.pot

@@ -27391,6 +27391,9 @@ msgstr ""
 msgid "Projects with no vulnerabilities and security scanning enabled"
 msgstr ""
 
+msgid "Projects with this topic"
+msgstr ""
+
 msgid "Projects with write access"
 msgstr ""
 

spec/controllers/explore/projects_controller_spec.rb

@@ -74,6 +74,28 @@ RSpec.describe Explore::ProjectsController do
         end
       end
     end
+
+    describe 'GET #topic' do
+      context 'when topic does not exist' do
+        it 'renders a 404 error' do
+          get :topic, params: { topic_name: 'topic1' }
+
+          expect(response).to have_gitlab_http_status(:not_found)
+        end
+      end
+      context 'when topic exists' do
+        before do
+          create(:topic, name: 'topic1')
+        end
+
+        it 'renders the template' do
+          get :topic, params: { topic_name: 'topic1' }
+
+          expect(response).to have_gitlab_http_status(:ok)
+          expect(response).to render_template('topic')
+        end
+      end
+    end
   end
 
   shared_examples "blocks high page numbers" do

spec/features/dashboard/projects_spec.rb

@@ -204,7 +204,7 @@ RSpec.describe 'Dashboard Projects' do
         visit dashboard_projects_path
 
         expect(page).to have_selector('[data-testid="project_topic_list"]')
-        expect(page).to have_link('topic1', href: explore_projects_path(topic: 'topic1'))
+        expect(page).to have_link('topic1', href: topic_explore_projects_path(topic_name: 'topic1'))
       end
     end
 

spec/features/projects_spec.rb

@@ -133,7 +133,7 @@ RSpec.describe 'Project' do
       visit path
 
       expect(page).to have_selector('[data-testid="project_topic_list"]')
-      expect(page).to have_link('topic1', href: explore_projects_path(topic: 'topic1'))
+      expect(page).to have_link('topic1', href: topic_explore_projects_path(topic_name: 'topic1'))
     end
 
     it 'shows up to 3 project topics' do
@@ -142,9 +142,9 @@ RSpec.describe 'Project' do
       visit path
 
       expect(page).to have_selector('[data-testid="project_topic_list"]')
-      expect(page).to have_link('topic1', href: explore_projects_path(topic: 'topic1'))
-      expect(page).to have_link('topic2', href: explore_projects_path(topic: 'topic2'))
-      expect(page).to have_link('topic3', href: explore_projects_path(topic: 'topic3'))
+      expect(page).to have_link('topic1', href: topic_explore_projects_path(topic_name: 'topic1'))
+      expect(page).to have_link('topic2', href: topic_explore_projects_path(topic_name: 'topic2'))
+      expect(page).to have_link('topic3', href: topic_explore_projects_path(topic_name: 'topic3'))
       expect(page).to have_content('+ 1 more')
     end
   end

spec/features/topic_show_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe 'Topic show page' do
+  let_it_be(:topic) { create(:topic, name: 'my-topic', description: 'This is **my** topic https://google.com/ :poop: ```\ncode\n```', avatar: fixture_file_upload("spec/fixtures/dk.png", "image/png")) }
+
+  context 'when topic does not exist' do
+    let(:path) { topic_explore_projects_path(topic_name: 'non-existing') }
+
+    it 'renders 404' do
+      visit path
+
+      expect(status_code).to eq(404)
+    end
+  end
+
+  context 'when topic exists' do
+    before do
+      visit topic_explore_projects_path(topic_name: topic.name)
+    end
+
+    it 'shows name, avatar and description as markdown' do
+      expect(page).to have_content(topic.name)
+      expect(page).to have_selector('.avatar-container > img.topic-avatar')
+      expect(find('.topic-description')).to have_selector('p > strong')
+      expect(find('.topic-description')).to have_selector('p > a[rel]')
+      expect(find('.topic-description')).to have_selector('p > gl-emoji')
+      expect(find('.topic-description')).to have_selector('p > code')
+    end
+
+    context 'with associated projects' do
+      let!(:project) { create(:project, :public, topic_list: topic.name) }
+
+      it 'shows project list' do
+        visit topic_explore_projects_path(topic_name: topic.name)
+
+        expect(find('.projects-list .project-name')).to have_content(project.name)
+      end
+    end
+
+    context 'without associated projects' do
+      it 'shows correct empty state message' do
+        expect(page).to have_content('Explore public groups to find projects to contribute to.')
+      end
+    end
+  end
+end