DEV: Run system tests for official themes (#24378)

Why this change?

As the number of themes which the Discourse team supports officially
grows, we want to ensure that changes made to Discourse core do not
break the plugins. As such, we are adding a step to our Github actions
test job to run the system tests for all official themes.

What does this change do?

This change adds a step to our Github actions test job to run the system
tests for all official plugins. This is achieved by the introduction of
the `themes:install_all_official` Rake task which installs all the
themes that are officially supported by the Discourse team.

.github/workflows/tests.yml

@@ -41,11 +41,17 @@ jobs:
 
       matrix:
         build_type: [backend, frontend, system, annotations]
-        target: [core, plugins]
+        target: [core, plugins, themes]
         ruby: ["3.2"]
         exclude:
           - build_type: annotations
             target: plugins
+          - build_type: annotations
+            target: themes
+          - build_type: frontend
+            target: themes
+          - build_type: backend
+            target: themes
           - build_type: frontend
             target: core # Handled by core_frontend_tests job (below)
         include:
@@ -113,6 +119,10 @@ jobs:
         if: matrix.target == 'plugins'
         run: bin/rake plugin:pull_compatible_all
 
+      - name: Checkout official themes
+        if: matrix.target == 'themes'
+        run: bin/rake themes:clone_all_official
+
       - name: Add hosts to /etc/hosts, otherwise Chrome cannot reach minio
         run: |
           echo "127.0.0.1 minio.local" | sudo tee -a /etc/hosts
@@ -243,6 +253,13 @@ jobs:
         run: LOAD_PLUGINS=1 RAILS_ENABLE_TEST_LOG=1 RAILS_TEST_LOG_LEVEL=error PARALLEL_TEST_PROCESSORS=4 bin/turbo_rspec --use-runtime-info --profile=50 --verbose --format documentation plugins/chat/spec/system
         timeout-minutes: 30
 
+      - name: Theme System Tests
+        if: matrix.build_type == 'system' && matrix.target == 'themes'
+        run: |
+          RAILS_ENABLE_TEST_LOG=1 RAILS_TEST_LOG_LEVEL=error PARALLEL_TEST_PROCESSORS=4 bin/turbo_rspec --profile=50 --verbose --format documentation tmp/themes/*/spec/system
+        shell: bash
+        timeout-minutes: 30
+
       - name: Upload failed system test screenshots
         uses: actions/upload-artifact@v3
         if: matrix.build_type == 'system' && failure()

lib/tasks/themes.rake

@@ -194,3 +194,26 @@ ensure
   db&.remove
   redis&.remove
 end
+
+desc "Clones all official themes."
+task "themes:clone_all_official" do |task, args|
+  require "theme_metadata"
+  FileUtils.rm_rf("tmp/themes")
+
+  official_themes =
+    ThemeMetadata::OFFICIAL_THEMES.each do |theme_name|
+      repo = "https://github.com/discourse/#{theme_name}"
+      path = File.expand_path("tmp/themes/#{theme_name}")
+
+      attempts = 0
+
+      begin
+        attempts += 1
+        system("git clone #{repo} #{path}", exception: true)
+      rescue StandardError
+        abort("Failed to clone #{repo}") if attempts >= 3
+        STDERR.puts "Failed to clone #{repo}... trying again..."
+        retry
+      end
+    end
+end

lib/theme_metadata.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+class ThemeMetadata
+  OFFICIAL_THEMES =
+    Set.new(
+      %w[
+        discourse-brand-header
+        discourse-category-banners
+        discourse-clickable-topic
+        discourse-color-scheme-toggle
+        discourse-custom-header-links
+        Discourse-easy-footer
+        discourse-gifs
+        discourse-topic-thumbnails
+        discourse-search-banner
+        discourse-unanswered-filter
+        discourse-versatile-banner
+        DiscoTOC
+        unformatted-code-detector
+      ],
+    ).to_a
+end