From fef8a18bfb8c3a09395d91fdab97985ed6cd97e6 Mon Sep 17 00:00:00 2001
From: Thales Macedo Garitezi <thalesmg@gmail.com>
Date: Fri, 17 Dec 2021 16:31:04 -0300
Subject: [PATCH] chore(update_appup): insert `load_module`s after
 `application:stop`

If there is already any `application:stop(Application)` call in the
appup instructions, we prefer to add `load_module` instructions after
it, so we can be sure that the load is replaced safely.
---
 scripts/update_appup.escript | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/scripts/update_appup.escript b/scripts/update_appup.escript
index 530f15072..efd98b046 100755
--- a/scripts/update_appup.escript
+++ b/scripts/update_appup.escript
@@ -298,8 +298,11 @@ do_merge_update_actions(App, Vsn, {New0, Changed0, Deleted0}, OldActions) ->
     Reloads = [{load_module, M, brutal_purge, soft_purge, []}
                || not contains_restart_application(App, OldActions),
                   M <- Changed ++ New],
-    Reloads ++
-        OldActions ++
+    {OldActionsWithStop, OldActionsAfterStop} =
+        find_application_stop_instruction(App, OldActions),
+    OldActionsWithStop ++
+        Reloads ++
+        OldActionsAfterStop ++
         [{delete_module, M} || M <- Deleted] ++
         AppSpecific.
 
@@ -308,6 +311,23 @@ do_merge_update_actions(App, Vsn, {New0, Changed0, Deleted0}, OldActions) ->
 contains_restart_application(Application, Actions) ->
     lists:member({restart_application, Application}, Actions).
 
+%% If there is an `application:stop(Application)' call in the
+%% instructions, we insert `load_module' instructions after it.
+find_application_stop_instruction(Application, Actions) ->
+    {Before, After0} =
+        lists:splitwith(
+          fun({apply, {application, stop, [Application]}}) ->
+                  false;
+             (_) ->
+                  true
+          end, Actions),
+    case After0 of
+        [StopInst | After] ->
+            {Before ++ [StopInst], After};
+        [] ->
+            {[], Before}
+    end.
+
 %% @doc Process the existing actions to exclude modules that are
 %% already handled
 process_old_action({purge, Modules}) ->