Handle all kinds of errors in the workflow (#10)

* Handle all kinds of errors in the workflow

Handles all kinds of errors in the workflow, including "stop loop" (throw, exit)
errors from Erlang that could be sent from Finch lower in the stack.

Co-authored-by: Eric Iacutone <iacutone@protonmail.com>

* Addd tests to ensure we catch all kinds of errors

---------

Co-authored-by: Eric Iacutone <iacutone@protonmail.com>

lib/workflow.ex

@@ -1018,8 +1018,8 @@ defmodule Pacer.Workflow do
           :telemetry.span([:pacer, :execute_vertex], metadata, fn ->
             {Map.put(workflow, field, resolver.(workflow)), metadata}
           end)
-        rescue
-          _error ->
+        catch
+          _kind, _error ->
             workflow
         end
 
@@ -1040,7 +1040,7 @@ defmodule Pacer.Workflow do
     |> Enum.map(fn {field, resolver} ->
       dependencies = module.__graph__(:batched_field_dependencies, field)
       # We want to also pass the current value (which is the default) of the field itself,
-      # so that we can use it in the rescue/fallback clause
+      # so that we can use it in the fallback clause
       partial_workflow = Map.take(workflow, [field | dependencies])
       {field, partial_workflow, resolver}
     end)
@@ -1063,8 +1063,8 @@ defmodule Pacer.Workflow do
                Map.merge(%{parent_pid: parent_pid}, user_provided_metadata)}
             end
           )
-        rescue
-          _error ->
+        catch
+          _kind, _error ->
             {field, Map.get(partial_workflow, field)}
         end
       end,

test/workflow_test.exs

@@ -24,10 +24,39 @@ defmodule Pacer.WorkflowTest do
           dependencies: [:custom_field, :field_a],
           default: "this is a default value for request2"
         )
+
+        field(:elixir_raise,
+          resolver: &__MODULE__.elixir_raise/1,
+          dependencies: [:custom_field],
+          default: :elixir_raise
+        )
+
+        field(:erlang_throw,
+          resolver: &__MODULE__.erlang_throw/1,
+          dependencies: [:custom_field],
+          default: :erlang_throw
+        )
+
+        field(:erlang_exit,
+          resolver: &__MODULE__.erlang_exit/1,
+          dependencies: [:custom_field],
+          default: :erlang_exit
+        )
+
+        field(:erlang_error,
+          resolver: &__MODULE__.erlang_error/1,
+          dependencies: [:custom_field],
+          default: :erlang_error
+        )
       end
     end
 
     def do_work(_), do: :ok
+
+    def elixir_raise(_), do: raise("boom baby!")
+    def erlang_throw(_), do: :erlang.throw(:oops)
+    def erlang_exit(_), do: :erlang.exit(:no_reason)
+    def erlang_error(_), do: :erlang.error(:boom)
   end
 
   defmodule Resolvers do
@@ -160,7 +189,11 @@ defmodule Pacer.WorkflowTest do
              :field_a,
              :field_with_default,
              :request_1,
-             :request_2
+             :request_2,
+             :elixir_raise,
+             :erlang_throw,
+             :erlang_exit,
+             :erlang_error
            ]
   end
 
@@ -183,7 +216,14 @@ defmodule Pacer.WorkflowTest do
   end
 
   test "batch metadata" do
-    assert TestGraph.__graph__(:batch_fields, :http_requests) == [:request_1, :request_2]
+    assert TestGraph.__graph__(:batch_fields, :http_requests) == [
+             :request_1,
+             :request_2,
+             :elixir_raise,
+             :erlang_throw,
+             :erlang_exit,
+             :erlang_error
+           ]
 
     assert TestGraph.__graph__(:http_requests, :options) == [
              on_timeout: :kill_task,
@@ -220,11 +260,22 @@ defmodule Pacer.WorkflowTest do
 
     {:batch, batch_resolvers} = TestGraph.__graph__(:resolver, :http_requests)
 
-    assert Enum.count(batch_resolvers) == 2,
-           "Expected http_requests batch node to have 2 resolvers. Got #{inspect(batch_resolvers)}"
+    num_resolvers = Enum.count(batch_resolvers)
+
+    assert num_resolvers == 6,
+           "Expected http_requests batch node to have 3 resolvers. Got #{num_resolvers}:\n
+           #{inspect(batch_resolvers)}"
 
     Enum.each(batch_resolvers, fn {field_name, resolver} ->
-      assert field_name in [:request_1, :request_2]
+      assert field_name in [
+               :request_1,
+               :request_2,
+               :elixir_raise,
+               :erlang_throw,
+               :erlang_exit,
+               :erlang_error
+             ]
+
       assert is_function(resolver, 1)
     end)
   end