Handle case when restoring process without saved variables

Author: ashton314

lib/chorex/runtime.ex

@@ -56,6 +56,9 @@ defmodule Chorex.Runtime do
       # knock off the recover frame
       |> Enum.drop(1)
 
+    # Restore vars if given; see note in RuntimeMonitor.recover
+    vars = if is_map(vars), do: vars, else: state.vars
+
     state = %{state | config: new_network, stack: new_stack, vars: vars}
 
     continue_on_stack(nil, state)

lib/chorex/runtime_monitor.ex

@@ -297,8 +297,14 @@ defmodule Chorex.RuntimeMonitor do
   Called for effect; no meaningful return value.
   """
   def recover(name, pid, new_config, barrier_token, state) do
-    {_, recover_state} = assoc_get(state.state_store[name], barrier_token)
-    send(pid, {:recover, state.session_token, new_config, barrier_token, recover_state.vars})
+    case assoc_get(state.state_store[name], barrier_token) do
+      {_, recover_state} ->
+        send(pid, {:recover, state.session_token, new_config, barrier_token, recover_state.vars})
+
+      nil ->
+        # Sometimes no state has been saved yet; in this case, don't bother restoring variables
+        send(pid, {:recover, state.session_token, new_config, barrier_token, nil})
+    end
     :ok
   end
 

lib/utils.ex

@@ -49,6 +49,8 @@ defmodule Utils do
   #       _ -> true
   #     end)
 
+  # Lispy: treat nil like []
+  def assoc_get(nil, _), do: nil
   def assoc_get(alist, k),
     do:
       Enum.find(alist, fn