Deprecation warning instead of raising error

CHANGELOG.md

@@ -2,7 +2,7 @@ Unreleased
 ----------
 * Fixes a bug with `EnsureAuthenticatedLinks` causing deep links to not work [#1549](https://github.com/Shopify/shopify_app/pull/1549)
 * Ensure online token is properly used when using `current_shopify_session` [#1566](https://github.com/Shopify/shopify_app/pull/1566)
-* Detect the use of incompatible controller concerns [#1560](https://github.com/Shopify/shopify_app/pull/1560). Depending on how your app is structured, this may result in an error on startup even though the app was working correctly. However, it is helping exposing an existing flaw that may have caused issues in future.
+* Log a deprecation warning for the use of incompatible controller concerns [#1560](https://github.com/Shopify/shopify_app/pull/1560). Depending on how your app is structured, this may result in an error on startup even though the app was working correctly. However, it is helping exposing an existing flaw that may have caused issues in future.
 
 21.2.0 (Oct 25, 2022)
 ----------

app/controllers/concerns/shopify_app/require_known_shop.rb

@@ -7,9 +7,11 @@ module RequireKnownShop
 
     included do
       if ancestors.include?(ShopifyApp::LoginProtection)
-        raise ConfigurationError,
-          "You are attempting to use both RequireKnownShop and LoginProtection in the same controller. "\
-            "These are not compatible."
+        ActiveSupport::Deprecation.warn(<<~EOS)
+          We detected the use of incompatible concerns (RequireKnownShop and LoginProtection) in #{name},
+          which may lead to unpredictable behavior. In a future release of this library this will raise an error.
+        EOS
+
       end
 
       before_action :check_shop_domain

lib/shopify_app/controller_concerns/login_protection.rb

@@ -10,9 +10,10 @@ module LoginProtection
 
     included do
       if ancestors.include?(ShopifyApp::RequireKnownShop)
-        raise ConfigurationError,
-          "You are attempting to use both RequireKnownShop and LoginProtection in the same controller. "\
-            "These are not compatible."
+        ActiveSupport::Deprecation.warn(<<~EOS)
+          We detected the use of incompatible concerns (RequireKnownShop and LoginProtection) in #{name},
+          which may lead to unpredictable behavior. In a future release of this library this will raise an error.
+        EOS
       end
 
       after_action :set_test_cookie

test/controllers/concerns/require_known_shop_test.rb

@@ -62,18 +62,28 @@ def index
   end
 
   test "detects incompatible controller concerns" do
-    assert_raises ShopifyApp::ConfigurationError do
+    assert_deprecated(/incompatible concerns/) do
       Class.new(ApplicationController) do
         include ShopifyApp::RequireKnownShop
         include ShopifyApp::LoginProtection
       end
     end
 
-    assert_raises ShopifyApp::ConfigurationError do
+    assert_deprecated(/incompatible concerns/) do
       Class.new(ApplicationController) do
         include ShopifyApp::RequireKnownShop
         include ShopifyApp::Authenticated # since this indirectly includes LoginProtection
       end
     end
+
+    assert_deprecated(/incompatible concerns/) do
+      authenticated_controller = Class.new(ApplicationController) do
+        include ShopifyApp::Authenticated
+      end
+
+      Class.new(authenticated_controller) do
+        include ShopifyApp::RequireKnownShop
+      end
+    end
   end
 end

test/shopify_app/controller_concerns/login_protection_test.rb

@@ -467,7 +467,7 @@ class LoginProtectionControllerTest < ActionController::TestCase
   end
 
   test "detects incompatible controller concerns" do
-    assert_raises ShopifyApp::ConfigurationError do
+    assert_deprecated(/incompatible concerns/) do
       Class.new(ApplicationController) do
         include ShopifyApp::LoginProtection
         include ShopifyApp::RequireKnownShop