Include exception causes into log messages

Author: fatkodima

actionpack/lib/action_dispatch/middleware/debug_exceptions.rb

@@ -141,6 +141,12 @@ def log_error(request, wrapper)
         message = []
         message << "  "
         message << "#{wrapper.exception_class_name} (#{wrapper.message}):"
+        if wrapper.has_cause?
+          message << "\nCauses:"
+          wrapper.wrapped_causes.each do |wrapped_cause|
+            message << "#{wrapped_cause.exception_class_name} (#{wrapped_cause.message})"
+          end
+        end
         message.concat(wrapper.annotated_source_code)
         message << "  "
         message.concat(trace)

actionpack/test/dispatch/debug_exceptions_test.rb

@@ -615,6 +615,25 @@ def self.build_app(app, *args)
     assert_not_empty (output.rewind && output.read).lines
   end
 
+  test "logs exception causes" do
+    @app = DevelopmentApp
+
+    output = StringIO.new
+
+    env = { "action_dispatch.show_exceptions"       => :all,
+            "action_dispatch.logger"                => Logger.new(output),
+            "action_dispatch.log_rescued_responses" => true }
+
+    get "/nested_exceptions", headers: env
+    assert_response 500
+    log = output.rewind && output.read
+    assert_includes log, <<~MSG
+      Causes:
+      RuntimeError (Second error)
+      RuntimeError (First error)
+    MSG
+  end
+
   test "display backtrace when error type is SyntaxError" do
     @app = DevelopmentApp