chore: reduce function nesting depth to satisfy credo

Flatten nested `if`/`with`/`case` blocks in `StartChild.undo/4` and
`ProcessExit.run/3` to stay within the max nesting depth of 2.

Author: jimsynz

lib/reactor/process/step/process_exit.ex

@@ -55,15 +55,19 @@ defmodule Reactor.Process.Step.ProcessExit do
          {:ok, options} <- Spark.Options.validate(options, @opt_schema),
          {:ok, process} <- Keyword.fetch(arguments, :process),
          {:ok, reason} <- Keyword.fetch(arguments, :reason) do
-      if options[:wait_for_exit?] do
-        case terminate(process, reason, arguments[:timeout], context.current_step) do
-          :ok -> {:ok, reason}
-          {:error, reason} -> {:error, reason}
-        end
-      else
-        Process.exit(process, reason)
-        {:ok, reason}
+      send_exit(process, reason, arguments[:timeout], options, context)
+    end
+  end
+
+  defp send_exit(process, reason, timeout, options, context) do
+    if options[:wait_for_exit?] do
+      case terminate(process, reason, timeout, context.current_step) do
+        :ok -> {:ok, reason}
+        {:error, reason} -> {:error, reason}
       end
+    else
+      Process.exit(process, reason)
+      {:ok, reason}
     end
   end
 end

lib/reactor/process/step/start_child.ex

@@ -101,16 +101,15 @@ defmodule Reactor.Process.Step.StartChild do
   @impl true
   def undo(pid, arguments, context, options) do
     with {:ok, arguments} <- Spark.Options.validate(Enum.to_list(arguments), @arg_schema),
-         {:ok, options} <- Spark.Options.validate(options, @opt_schema) do
-      if Keyword.get(options, :terminate_on_undo?, true) do
-        with {:ok, %{id: id}} <- child_spec(arguments[:child_spec]) do
-          ref = Process.monitor(pid)
-          options[:module].terminate_child(arguments[:supervisor], id)
-          await_exit(pid, ref, options[:termination_timeout], context.current_step)
-        end
-      else
-        :ok
-      end
+         {:ok, options} <- Spark.Options.validate(options, @opt_schema),
+         true <- Keyword.get(options, :terminate_on_undo?, true),
+         {:ok, %{id: id}} <- child_spec(arguments[:child_spec]) do
+      ref = Process.monitor(pid)
+      options[:module].terminate_child(arguments[:supervisor], id)
+      await_exit(pid, ref, options[:termination_timeout], context.current_step)
+    else
+      false -> :ok
+      error -> error
     end
   end