Fix: Detect and warn when schedules generate multiple CRONs

app/models/solid_queue/recurring_task.rb

@@ -103,7 +103,10 @@ def attributes_for_upsert
 
     private
       def supported_schedule
-        unless parsed_schedule.instance_of?(Fugit::Cron)
+        if parsed_schedule == :multiple_crons_detected
+          errors.add :schedule, :multiple_crons,
+            message: "generates multiple cron schedules. Please use separate recurring tasks for each schedule, or use explicit cron syntax (e.g., '40 0,15 * * *' for multiple times with the same minutes)"
+        elsif !parsed_schedule.instance_of?(Fugit::Cron)
           errors.add :schedule, :unsupported, message: "is not a supported recurring schedule"
         end
       end
@@ -152,7 +155,15 @@ def arguments_with_kwargs
 
 
       def parsed_schedule
-        @parsed_schedule ||= Fugit.parse(schedule)
+        @parsed_schedule ||= begin
+          Fugit::Nat.parse(schedule, multi: :fail) || Fugit.parse(schedule)
+        rescue ArgumentError => e
+          if e.message.include?("multiple crons")
+            :multiple_crons_detected
+          else
+            raise
+          end
+        end
       end
 
       def job_class

test/models/solid_queue/recurring_task_test.rb

@@ -144,6 +144,25 @@ def perform
     assert_not SolidQueue::RecurringTask.new(key: "task-id", class_name: "SolidQueue::RecurringTaskTest::JobWithoutArguments").valid?
   end
 
+  test "schedules with multiple cron detection" do
+    task = recurring_task_with(class_name: "JobWithoutArguments", schedule: "every day at 00:40")
+    assert task.valid?
+    assert task.to_s.ends_with? "[ 40 0 * * * ]"
+
+    task = recurring_task_with(class_name: "JobWithoutArguments", schedule: "every day at 00:40 and 15:40")
+    assert task.valid?
+    assert task.to_s.ends_with? "[ 40 0,15 * * * ]"
+
+    task = recurring_task_with(class_name: "JobWithoutArguments", schedule: "every day at 00:40 and 15:20")
+    assert_not task.valid?
+    error_message = task.errors[:schedule].first
+    assert_includes error_message, "generates multiple cron schedules"
+    assert_includes error_message, "Please use separate recurring tasks"
+
+    task = recurring_task_with(class_name: "JobWithoutArguments", schedule: "40 0 * * *")
+    assert task.valid?
+  end
+
   test "valid and invalid job class and command" do
     # Command
     assert recurring_task_with(command: "puts '¡hola!'").valid?