Raise may call an atom - undefined module

[tomdos]

There is an issue in catching an exit here https://github.com/joaomdmoura/machinery/blob/master/lib/machinery.ex#L95

The raise expect a module or a string. However it may get an atom and Elixir will try to call exception/1 from that atom which obviously fails.

How to reproduce it:

Machinery.transition_to(A, :b_parma, :c_param)

Output:

17:15:41.494 [error] GenServer Machinery.Transitions terminating
** (UndefinedFunctionError) function :b_parma._machinery_initial_state/0 is undefined (module :b_parma is not available)
    :b_parma._machinery_initial_state()
    (machinery) lib/machinery/transitions.ex:24: Machinery.Transitions.handle_call/3
    (stdlib) gen_server.erl:661: :gen_server.try_handle_call/4
    (stdlib) gen_server.erl:690: :gen_server.handle_msg/6
    (stdlib) proc_lib.erl:249: :proc_lib.init_p_do_apply/3
Last message (from #PID<0.1595.0>): {:run, A, :b_parma, :c_param}
** (UndefinedFunctionError) function :undef.exception/1 is undefined (module :undef is not available)
    :undef.exception([])
    (machinery) lib/machinery.ex:113: Machinery.transition_to/3

As you can see I used undefined module and this gets to raise which tries to call :undef.exception/1 which is undefined as well.

Maybe as a quick fix changing raise to throw may work or removing catching at all?

[joaomdmoura]

Good catch @tomdos! I'll look into it next week and try to cut a new minor version with the fix

[dfang]

@joaomdmoura i got a similar error:

** (UndefinedFunctionError) function :calling_self.exception/1 is undefined (module :calling_self is not available)
    (machinery 1.0.0) lib/machinery/transition.ex:142: Machinery.Transition.callbacks_fallback/4
    (machinery 1.0.0) lib/machinery/transitions.ex:52: Machinery.Transitions.handle_call/3
    (stdlib 3.14) gen_server.erl:715: :gen_server.try_handle_call/4
    (stdlib 3.14) gen_server.erl:744: :gen_server.handle_msg/6
    (stdlib 3.14) proc_lib.erl:226: :proc_lib.init_p_do_apply/3
Last message (from #PID<0.4315.0>): {:run, %Tiktok.Orders.OrderDetail{__meta__: #Ecto.Schema.Metadata<:loaded, "order_details">, amount: 9197443, category_id: 2, id: 335, inserted_at: ~U[2022-01-24 04:35:18Z], name: "xxx, order: #Ecto.Association.NotLoaded<association :order is not loaded>, order_id: 34, resolved_at: nil, state: "pending", updated_at: ~U[2022-01-24 04:35:18Z]}, Tiktok.Orders.OrderDetailStateMachine, "resolved"}
13:08:04.940 [info] Application machinery exited: shutdown

and errors from oban

{"{\"at\": \"2022-01-24T05:46:51.250284Z\", \"error\": \"** (UndefinedFunctionError) function :noproc.exception/1 is undefined (module :noproc is not available)\\n    :noproc.exception([])\\n    (machinery 1.0.0) lib/machinery.ex:109: Machinery.transition_to/3\\n    (tiktok 0.1.0) lib/tiktok/workers/simulators/resolve_order_detail_simulator.ex:67: Tiktok.Workers.Simulators.ResolveOrderDetailSimulator.perform/1\\n    (oban 2.9.2) lib/oban/queue/executor.ex:212: Oban.Queue.Executor.perform_inline/2\\n    (oban 2.9.2) lib/oban/queue/executor.ex:200: Oban.Queue.Executor.perform_inline/2\\n    (oban 2.9.2) lib/oban/queue/executor.ex:82: Oban.Queue.Executor.call/1\\n    (elixir 1.12.3) lib/task/supervised.ex:90: Task.Supervised.invoke_mfa/2\\n    (elixir 1.12.3) lib/task/supervised.ex:35: Task.Supervised.reply/5\\n    (stdlib 3.14) proc_lib.erl:226: :proc_lib.init_p_do_apply/3\\n\", \"attempt\": 1}"}