Ash.Flow Error handling

Ash Forum Ash Questions / Help
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1

I want to be able to do something like this, but Flow just errors out when my step that Flow “returns” outputs {:error, reason} rather than returning :ok or :error tuples. Is there a way to make this work?

   MyFlow.run() 
     |> case do
       {:ok, _} -> "success"
       {:error, reason} -> reason
     end

The documentation states this, so it doesn’t sound like it returns an error tuple. (I will be happy to be wrong)

Currently, any error anywhere in the flow will fail the flow and will return an error. Over time, error handling behavior will be added,

Error stacktrace

[error] GenServer #PID<0.12304.0> terminating
** (Ash.Error.Unknown) Unknown Error

* Oops, there was an error.
    at update_task_instance_status_transaction, create_instance_approval
  (ash 2.17.7) lib/ash/error/error.ex:391: Ash.Error.to_ash_error/3
  (ash 2.17.7) lib/ash/engine/request.ex:228: Ash.Engine.Request.next/1
  (ash 2.17.7) lib/ash/engine/engine.ex:712: Ash.Engine.advance_request/2
  (ash 2.17.7) lib/ash/engine/engine.ex:637: Ash.Engine.fully_advance_request/2
  (ash 2.17.7) lib/ash/engine/engine.ex:578: Ash.Engine.do_run_iteration/2
  (elixir 1.15.5) lib/enum.ex:2510: Enum."-reduce/3-lists^foldl/2-0-"/3
  (ash 2.17.7) lib/ash/engine/engine.ex:307: Ash.Engine.run_to_completion/1
  (ash 2.17.7) lib/ash/engine/engine.ex:252: Ash.Engine.do_run/2
  (ash 2.17.7) lib/ash/engine/engine.ex:114: anonymous fn/3 in Ash.Engine.run/2
  (ash 2.17.7) lib/ash/data_layer/data_layer.ex:337: Ash.DataLayer.transaction/4
  (ash 2.17.7) lib/ash/data_layer/data_layer.ex:322: anonymous fn/5 in Ash.DataLayer.transaction/4
  (ash 2.17.7) lib/ash/data_layer/data_layer.ex:337: Ash.DataLayer.transaction/4
  (ash 2.17.7) lib/ash/data_layer/data_layer.ex:322: anonymous fn/5 in Ash.DataLayer.transaction/4
  (ash 2.17.7) lib/ash/data_layer/data_layer.ex:337: Ash.DataLayer.transaction/4
  (ash 2.17.7) lib/ash/data_layer/data_layer.ex:322: anonymous fn/5 in Ash.DataLayer.transaction/4
  (ecto_sql 3.11.0) lib/ecto/adapters/sql.ex:1358: anonymous fn/3 in Ecto.Adapters.SQL.checkout_or_transaction/4
  (db_connection 2.6.0) lib/db_connection.ex:1710: DBConnection.run_transaction/4
    (ash 2.17.7) lib/ash/flow/flow.ex:26: Ash.Flow.run!/3
2

:thinking: It should return an error. This is likely a bug. Can you report as much detail as you can and I’ll take a look this week?

3

Opened an issue here. Flow.run crashing without returning an error tuple · Issue #797 · ash-project/ash · GitHub

Will do some more testing and try to add more details. Thank you.

1 Like
4

It was a user error. Should have used Flow.run not run!.