Respond with 422 for non-GET HTML requests with errors

When responding to a non-GET HTML request that had errors on the
resource, responders would not set any status, which means Rails would
default to `200 OK`. This has been long working like this but also a
long discussion in responders to change that behavior, to be more inline
with how other types of requests (like JSON/XML) handle responses by
setting the HTTP status to 422 Unprocessable Entity when responding with
an error.

More recently with the Turbo/Hotwire library, they've added support to
render form responses as errors with 4xx statuses [1], so it makes even
more sense for responders to make the move here.

This change now makes responders use the 422 Unprocessable Entity status
in such cases when the resource has errors, and should work more out of
the box with Turbo/Hotwire.

Please note that this is a possible breaking change if you're relying on
the previous status to trigger any behavior for errors in your app.

[1] hotwired/turbo#39

CHANGELOG.md

@@ -1,8 +1,9 @@
 ## Unreleased
 
-* Add support for Ruby 3.0, drop support for Ruby < 2.5
-* Add support for Rails 6.1, drop support for Rails < 5.2
-* Move CI to GitHub Actions
+* Responding to an `HTML` request that has errors on the resource now sets the status to `422 Unprocessable Entity`. (instead of the default of `200 OK`.) This makes it more consistent with other statuses more commonly used in APIs (JSON/XML for example), and works by default with Turbo/Hotwire. Note that this change may break your application if you're relying on the previous 2xx status to handle error cases.
+* Add support for Ruby 3.0, drop support for Ruby < 2.5.
+* Add support for Rails 6.1, drop support for Rails < 5.2.
+* Move CI to GitHub Actions.
 
 ## 3.0.1
 

lib/action_controller/responder.rb

@@ -202,7 +202,7 @@ def navigation_behavior(error)
       if get?
         raise error
       elsif has_errors? && default_action
-        render rendering_options
+        render error_rendering_options
       else
         redirect_to navigation_location
       end
@@ -300,11 +300,11 @@ def response_overridden?
       @default_response.present?
     end
 
-    def rendering_options
+    def error_rendering_options
       if options[:render]
         options[:render]
       else
-        { action: default_action }
+        { action: default_action, status: :unprocessable_entity }
       end
     end
   end

test/action_controller/respond_with_test.rb

@@ -245,13 +245,13 @@ def test_using_resource_for_post_with_html_redirects_on_success
     end
   end
 
-  def test_using_resource_for_post_with_html_rerender_on_failure
+  def test_using_resource_for_post_with_html_rerender_and_yields_unprocessable_entity_on_failure
     with_test_route_set do
       errors = { name: :invalid }
       Customer.any_instance.stubs(:errors).returns(errors)
       post :using_resource
       assert_equal "text/html", @response.media_type
-      assert_equal 200, @response.status
+      assert_equal 422, @response.status
       assert_equal "New world!\n", @response.body
       assert_nil @response.location
     end
@@ -305,26 +305,26 @@ def test_using_resource_for_patch_with_html_redirects_on_success
     end
   end
 
-  def test_using_resource_for_patch_with_html_rerender_on_failure
+  def test_using_resource_for_patch_with_html_rerender_and_yields_unprocessable_entity_on_failure
     with_test_route_set do
       errors = { name: :invalid }
       Customer.any_instance.stubs(:errors).returns(errors)
       patch :using_resource
       assert_equal "text/html", @response.media_type
-      assert_equal 200, @response.status
+      assert_equal 422, @response.status
       assert_equal "Edit world!\n", @response.body
       assert_nil @response.location
     end
   end
 
-  def test_using_resource_for_patch_with_html_rerender_on_failure_even_on_method_override
+  def test_using_resource_for_patch_with_html_rerender_and_yields_unprocessable_entity_on_failure_even_on_method_override
     with_test_route_set do
       errors = { name: :invalid }
       Customer.any_instance.stubs(:errors).returns(errors)
       @request.env["rack.methodoverride.original_method"] = "POST"
       patch :using_resource
       assert_equal "text/html", @response.media_type
-      assert_equal 200, @response.status
+      assert_equal 422, @response.status
       assert_equal "Edit world!\n", @response.body
       assert_nil @response.location
     end
@@ -340,27 +340,27 @@ def test_using_resource_for_put_with_html_redirects_on_success
     end
   end
 
-  def test_using_resource_for_put_with_html_rerender_on_failure
+  def test_using_resource_for_put_with_html_rerender_and_yields_unprocessable_entity_on_failure
     with_test_route_set do
       errors = { name: :invalid }
       Customer.any_instance.stubs(:errors).returns(errors)
       put :using_resource
 
       assert_equal "text/html", @response.media_type
-      assert_equal 200, @response.status
+      assert_equal 422, @response.status
       assert_equal "Edit world!\n", @response.body
       assert_nil @response.location
     end
   end
 
-  def test_using_resource_for_put_with_html_rerender_on_failure_even_on_method_override
+  def test_using_resource_for_put_with_html_rerender_and_yields_unprocessable_entity_on_failure_even_on_method_override
     with_test_route_set do
       errors = { name: :invalid }
       Customer.any_instance.stubs(:errors).returns(errors)
       @request.env["rack.methodoverride.original_method"] = "POST"
       put :using_resource
       assert_equal "text/html", @response.media_type
-      assert_equal 200, @response.status
+      assert_equal 422, @response.status
       assert_equal "Edit world!\n", @response.body
       assert_nil @response.location
     end