From 2c5215d3c9444ffa6f3f3656e994dcbcf5bb80d6 Mon Sep 17 00:00:00 2001
From: Gannon McGibbon <gannon.mcgibbon@gmail.com>
Date: Thu, 20 Aug 2026 18:12:21 -0500
Subject: [PATCH] Make default_render failures not set an error cause

A default_render that fails should not set a cause of a subsequent
api_behavior call if it results in an exception in Responder#to_format.
---
 lib/action_controller/responder.rb          | 14 +++++++-------
 test/action_controller/respond_with_test.rb |  8 ++++++++
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/lib/action_controller/responder.rb b/lib/action_controller/responder.rb
index 6937a41..d1462b2 100644
--- a/lib/action_controller/responder.rb
+++ b/lib/action_controller/responder.rb
@@ -192,14 +192,14 @@ def to_js
     # responds to :to_format and display it.
     #
     def to_format
-      if !get? && has_errors? && !response_overridden?
-        display_errors
-      elsif has_view_rendering? || response_overridden?
-        default_render
-      else
-        api_behavior
+      begin
+        if !get? && has_errors? && !response_overridden?
+          return display_errors
+        elsif has_view_rendering? || response_overridden?
+          return default_render
+        end
+      rescue ActionView::MissingTemplate
       end
-    rescue ActionView::MissingTemplate
       api_behavior
     end
 
diff --git a/test/action_controller/respond_with_test.rb b/test/action_controller/respond_with_test.rb
index 655248c..9f4000e 100644
--- a/test/action_controller/respond_with_test.rb
+++ b/test/action_controller/respond_with_test.rb
@@ -732,6 +732,14 @@ def test_raises_missing_renderer_if_an_api_behavior_with_no_renderer
     end
   end
 
+  def test_api_behavior_error_is_not_caused_by_missing_template
+    @controller = CsvRespondWithController.new
+    error = assert_raise ActionController::MissingRenderer do
+      get :index, format: "csv"
+    end
+    assert_nil error.cause
+  end
+
   def test_error_is_raised_if_no_respond_to_is_declared_and_respond_with_is_called
     @controller = EmptyRespondWithController.new
     @request.accept = "*/*"