Use a signal to prevent a user that the note balance is negative

apps/note/apps.py

@@ -3,7 +3,7 @@
 
 from django.apps import AppConfig
 from django.conf import settings
-from django.db.models.signals import post_save, pre_delete
+from django.db.models.signals import pre_delete, pre_save, post_save
 from django.utils.translation import gettext_lazy as _
 
 from . import signals
@@ -17,6 +17,15 @@ class NoteConfig(AppConfig):
         """
         Define app internal signals to interact with other apps
         """
+        pre_save.connect(
+            signals.pre_save_note,
+            sender="note.noteuser",
+        )
+        pre_save.connect(
+            signals.pre_save_note,
+            sender="note.noteclub",
+        )
+
         post_save.connect(
             signals.save_user_note,
             sender=settings.AUTH_USER_MODEL,

apps/note/models/notes.py

@@ -159,20 +159,6 @@ class NoteUser(Note):
     def pretty(self):
         return _("%(user)s's note") % {'user': str(self.user)}
 
-    @transaction.atomic
-    def save(self, *args, **kwargs):
-        if self.pk and self.balance < 0:
-            old_note = NoteUser.objects.get(pk=self.pk)
-            super().save(*args, **kwargs)
-            if old_note.balance >= 0:
-                # Passage en négatif
-                self.last_negative = timezone.now()
-                self._force_save = True
-                self.save(*args, **kwargs)
-                self.send_mail_negative_balance()
-        else:
-            super().save(*args, **kwargs)
-
     def send_mail_negative_balance(self):
         plain_text = render_to_string("note/mails/negative_balance.txt", dict(note=self))
         html = render_to_string("note/mails/negative_balance.html", dict(note=self))
@@ -201,20 +187,6 @@ class NoteClub(Note):
     def pretty(self):
         return _("Note of %(club)s club") % {'club': str(self.club)}
 
-    @transaction.atomic
-    def save(self, *args, **kwargs):
-        if self.pk and self.balance < 0:
-            old_note = NoteClub.objects.get(pk=self.pk)
-            super().save(*args, **kwargs)
-            if old_note.balance >= 0:
-                # Passage en négatif
-                self.last_negative = timezone.now()
-                self._force_save = True
-                self.save(*args, **kwargs)
-                self.send_mail_negative_balance()
-        else:
-            super().save(*args, **kwargs)
-
     def send_mail_negative_balance(self):
         plain_text = render_to_string("note/mails/negative_balance.txt", dict(note=self))
         html = render_to_string("note/mails/negative_balance.html", dict(note=self))

apps/note/signals.py

@@ -1,6 +1,8 @@
 # Copyright (C) 2018-2020 by BDE ENS Paris-Saclay
 # SPDX-License-Identifier: GPL-3.0-or-later
 
+from django.utils import timezone
+
 
 def save_user_note(instance, raw, **_kwargs):
     """
@@ -25,6 +27,16 @@ def save_club_note(instance, raw, **_kwargs):
         instance.note.save()
 
 
+def pre_save_note(instance, raw, **_kwargs):
+    if not raw and instance.pk and not hasattr(instance, "_no_signal") and instance.balance < 0:
+        from note.models import Note
+        old_note = Note.objects.get(pk=instance.pk)
+        if old_note.balance >= 0:
+            # Passage en négatif
+            instance.last_negative = timezone.now()
+            instance.send_mail_negative_balance()
+
+
 def delete_transaction(instance, **_kwargs):
     """
     Whenever we want to delete a transaction (caution with this), we ensure the transaction is invalid first.