Handle deleted workflows and snapshot failures in API

CHANGELOG.md

@@ -58,6 +58,9 @@ and this project adheres to
   project is opt-in. [#4919](https://github.com/OpenFn/lightning/issues/4919)
 - Fixed an issue where LOCAL_ADAPTORS is not respected by install_schemas task
   [#4943](https://github.com/OpenFn/lightning/issues/4943)
+- Return clean API errors when a workflow is deleted during save or its snapshot
+  cannot be saved, instead of allowing the workflows controller to crash.
+  [#4960](https://github.com/OpenFn/lightning/issues/4960)
 - Prevent AI Assistant channel joins from crashing when a chat references a
   deleted workflow or project. Missing records now fail authorization cleanly.
   [#4914](https://github.com/OpenFn/lightning/issues/4914)

lib/lightning_web/controllers/api/workflows_controller.ex

@@ -562,6 +562,19 @@ defmodule LightningWeb.API.WorkflowsController do
     |> json(%{id: workflow_id, errors: ["Not Found"]})
   end
 
+  defp maybe_handle_error(conn, {:error, :workflow_deleted}, workflow_id),
+    do: maybe_handle_error(conn, {:error, :not_found}, workflow_id)
+
+  defp maybe_handle_error(conn, {:error, reason}, workflow_id)
+       when reason in [:snapshot_failed, false] do
+    conn
+    |> put_status(:internal_server_error)
+    |> json(%{
+      id: workflow_id,
+      errors: ["Could not save the workflow snapshot."]
+    })
+  end
+
   defp maybe_handle_error(_conn, result, _workflow_id) when is_map(result),
     do: result
 

test/lightning_web/controllers/api/workflows_controller_test.exs

@@ -998,6 +998,55 @@ defmodule LightningWeb.API.WorkflowsControllerTest do
                |> json_response(404)
     end
 
+    test "returns 404 when the workflow is deleted before update", %{
+      conn: conn,
+      project: project
+    } do
+      workflow = insert(:simple_workflow, project: project)
+
+      workflow =
+        workflow
+        |> Ecto.Changeset.change(
+          deleted_at: DateTime.utc_now() |> DateTime.truncate(:second)
+        )
+        |> Repo.update!()
+
+      assert %{"id" => workflow_id, "errors" => ["Not Found"]} =
+               conn
+               |> patch(
+                 ~p"/api/projects/#{project.id}/workflows/#{workflow.id}",
+                 Jason.encode!(%{name: "work1.1"})
+               )
+               |> json_response(404)
+
+      assert workflow_id == workflow.id
+    end
+
+    test "returns 500 when the workflow snapshot cannot be saved", %{
+      conn: conn,
+      project: project
+    } do
+      workflow = insert(:simple_workflow, project: project)
+
+      insert(:snapshot,
+        workflow: workflow,
+        lock_version: workflow.lock_version + 1
+      )
+
+      assert %{
+               "id" => workflow_id,
+               "errors" => ["Could not save the workflow snapshot."]
+             } =
+               conn
+               |> patch(
+                 ~p"/api/projects/#{project.id}/workflows/#{workflow.id}",
+                 Jason.encode!(%{name: "work1.1"})
+               )
+               |> json_response(500)
+
+      assert workflow_id == workflow.id
+    end
+
     test "returns 409 when the workflow is being edited on the UI" do
       %{conn: conn, user: user} =
         register_and_log_in_user(%{conn: Phoenix.ConnTest.build_conn()})