Remove deprecated ability to assign a single value to `config.action_dispatch.trusted_proxies`

actionpack/CHANGELOG.md

@@ -1,3 +1,7 @@
+*   Remove deprecated ability to assign a single value to `config.action_dispatch.trusted_proxies`.
+
+    *Rafael Mendonça França*
+
 *   Deprecate `config.action_dispatch.return_only_request_media_type_on_content_type`.
 
     *Rafael Mendonça França*

actionpack/lib/action_dispatch/middleware/remote_ip.rb

@@ -64,9 +64,9 @@ module ActionDispatch
       elsif custom_proxies.respond_to?(:any?)
         custom_proxies
       else
-        ActionDispatch.deprecator.warn(<<~EOM)
-          Setting config.action_dispatch.trusted_proxies to a single value has
-          been deprecated. Please set this to an enumerable instead. For
+        raise(ArgumentError, <<~EOM)
+          Setting config.action_dispatch.trusted_proxies to a single value isn't
+          supported. Please set this to an enumerable instead. For
           example, instead of:
 
           config.action_dispatch.trusted_proxies = IPAddr.new("10.0.0.0/8")
@@ -75,10 +75,8 @@ module ActionDispatch
 
           config.action_dispatch.trusted_proxies = [IPAddr.new("10.0.0.0/8")]
 
-          Note that unlike passing a single argument, passing an enumerable
-          will *replace* the default set of trusted proxies.
+          Note that passing an enumerable will *replace* the default set of trusted proxies.
         EOM
-        Array(custom_proxies) + TRUSTED_PROXIES
       end
     end
 

guides/source/7_1_release_notes.md

@@ -52,6 +52,8 @@ Please refer to the [Changelog][action-pack] for detailed changes.
 
 *   Remove deprecated behavior on `Request#content_type`
 
+*   Remove deprecated ability to assign a single value to `config.action_dispatch.trusted_proxies`.
+
 ### Deprecations
 
 *   Deprecate `config.action_dispatch.return_only_request_media_type_on_content_type`.

railties/test/application/middleware/remote_ip_test.rb

@@ -84,14 +84,13 @@ module ApplicationTests
     end
 
     test "setting trusted proxies to a single value (deprecated) adds value to default trusted proxies" do
-      make_basic_app do |app|
-        app.config.action_dispatch.trusted_proxies = IPAddr.new("4.2.42.0/24")
+      exception = assert_raises(ArgumentError) do
+        make_basic_app do |app|
+          app.config.action_dispatch.trusted_proxies = IPAddr.new("4.2.42.0/24")
+        end
       end
 
-      assert_deprecated(/Setting config\.action_dispatch\.trusted_proxies to a single value/, ActionDispatch.deprecator) do
-        assert_equal "1.1.1.1",
-                     remote_ip("REMOTE_ADDR" => "1.1.1.1", "HTTP_X_FORWARDED_FOR" => "10.0.0.0,4.2.42.42")
-      end
+      assert_match(/Setting config\.action_dispatch\.trusted_proxies to a single value/, exception.message)
     end
   end
 end