Make EnsureAuthenticatedLinks compatible with AppBridge 2

app/controllers/concerns/shopify_app/ensure_authenticated_links.rb

@@ -10,9 +10,26 @@ module EnsureAuthenticatedLinks
 
     private
 
+    def splash_page
+      splash_page_with_params(shop: current_shopify_domain, host: params[:host])
+    end
+
+    def base_splash_page
+      root_path(return_to: request.fullpath)
+    end
+
+    def splash_page_with_params(params)
+      uri = URI(base_splash_page)
+      uri.query = CGI.parse(uri.query.to_s)
+        .symbolize_keys
+        .transform_values { |v| v.one? ? v.first : v }
+        .merge(params)
+        .to_query
+      uri.to_s
+    end
+
     def redirect_to_splash_page
-      splash_page_path = root_path(return_to: request.fullpath, shop: current_shopify_domain)
-      redirect_to(splash_page_path)
+      redirect_to(splash_page)
     rescue ShopifyApp::LoginProtection::ShopifyDomainNotFound => error
       Rails.logger.warn("[ShopifyApp::EnsureAuthenticatedLinks] Redirecting to login: [#{error.class}] "\
                          "Could not determine current shop domain")

test/controllers/concerns/ensure_authenticated_links_test.rb

@@ -36,10 +36,10 @@ def current_shopify_domain
     end
   end
 
-  test 'redirects to splash page with a return_to and shop param if no session token is present' do
-    get :some_link, params: { shop: @shop_domain }
+  test 'redirects to splash page with a return_to, shop and host params if no session token is present' do
+    get :some_link, params: { shop: @shop_domain, host: 'test-host' }
 
-    expected_path = root_path(return_to: request.fullpath, shop: @shop_domain)
+    expected_path = "/?host=test-host&return_to=#{CGI.escape(request.fullpath)}&shop=#{@shop_domain}"
 
     assert_redirected_to expected_path
   end