From 74630a9441fe3d6467db4336e3ea44b47c3ea4d6 Mon Sep 17 00:00:00 2001
From: Birger Schacht <birger.schacht@oeaw.ac.at>
Date: Tue, 7 May 2024 14:07:59 +0200
Subject: [PATCH] fix(history): use signal instead of method for setting
 timestamp

When doing a CASCADING delete, the `delete` method of an instance is not
called, but the `pre_delete` signal is triggered. We want to set the
current date for the `_history_date` attribute, if it is None. To do
that also in cascading deletes, we use the pre_delete signal.

Closes: #814
---
 apis_core/history/apps.py    | 3 +++
 apis_core/history/models.py  | 5 -----
 apis_core/history/signals.py | 9 +++++++++
 3 files changed, 12 insertions(+), 5 deletions(-)
 create mode 100644 apis_core/history/signals.py

diff --git a/apis_core/history/apps.py b/apis_core/history/apps.py
index 959a885a1..93c560959 100644
--- a/apis_core/history/apps.py
+++ b/apis_core/history/apps.py
@@ -3,3 +3,6 @@
 
 class HistoryConfig(AppConfig):
     name = "apis_core.history"
+
+    def ready(self):
+        from . import signals  # noqa: F401
diff --git a/apis_core/history/models.py b/apis_core/history/models.py
index d53059db7..9bd9afb97 100644
--- a/apis_core/history/models.py
+++ b/apis_core/history/models.py
@@ -148,11 +148,6 @@ def save(self, *args, **kwargs) -> None:
             self._history_date = timezone.now()
         return super().save(*args, **kwargs)
 
-    def delete(self, *args, **kwargs) -> tuple[int, dict[str, int]]:
-        if self._history_date is None:
-            self._history_date = datetime.now()
-        return super().delete(*args, **kwargs)
-
     def get_history_url(self):
         ct = ContentType.objects.get_for_model(self)
         return reverse("apis_core:history:history", args=[ct, self.id])
diff --git a/apis_core/history/signals.py b/apis_core/history/signals.py
new file mode 100644
index 000000000..23a4db7ea
--- /dev/null
+++ b/apis_core/history/signals.py
@@ -0,0 +1,9 @@
+from django.db.models.signals import pre_delete
+from django.dispatch import receiver
+from django.utils import timezone
+
+
+@receiver(pre_delete)
+def set_history_date(sender, instance, using, origin, **kwargs):
+    if getattr(instance, "_history_date", None) is None:
+        instance._history_date = timezone.now()