message style safely deletes without setting null

will set the related subscription to use the default instead

apps/api/serializers.py

@@ -243,6 +243,11 @@ class SubscriptionSerializer(DynamicModelSerializer):
     )
     channels_detail = serializers.SerializerMethodField()
     filters_detail = serializers.SerializerMethodField()
+    message_style = serializers.PrimaryKeyRelatedField(
+        queryset=MessageStyle.objects.all(),
+        required=True,
+        allow_null=False
+    )
     message_style_detail = serializers.SerializerMethodField()
     unique_rules_detail = serializers.SerializerMethodField()
 

apps/home/migrations/0015_alter_subscription_message_style.py

@@ -0,0 +1,19 @@
+# Generated by Django 5.0.4 on 2024-10-15 18:30
+
+import django.db.models.deletion
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('home', '0014_alter_discordchannel_id_alter_server_id'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='subscription',
+            name='message_style',
+            field=models.ForeignKey(null=True, on_delete=django.db.models.deletion.SET_NULL, to='home.messagestyle'),
+        ),
+    ]

apps/home/models.py

@@ -150,7 +150,13 @@ class MessageStyle(models.Model):
         if self.auto_created:
             raise ValidationError("Cannot delete 'MessageStyle' instance with 'auto_created=True'")
 
-        super().delete()
+        # If this style is being used, reset the users to the default style
+        default_message_style = MessageStyle.objects.get(server=self.server, auto_created=True)
+        Subscription.objects \
+            .filter(server=self.server, message_style=self) \
+            .update(message_style=default_message_style)
+
+        super().delete(*args, **kwargs)
 
     def __str__(self):
         return self.name
@@ -240,7 +246,7 @@ class Subscription(models.Model):
     publish_threshold = models.DateTimeField(default=timezone.now)
     channels = models.ManyToManyField(to=DiscordChannel, related_name="subscriptions", blank=False)
     filters = models.ManyToManyField(to=ContentFilter, blank=True)
-    message_style = models.ForeignKey(to=MessageStyle, on_delete=models.SET_NULL, null=True, blank=True)
+    message_style = models.ForeignKey(to=MessageStyle, on_delete=models.SET_NULL, null=True, blank=False)
     unique_rules = models.ManyToManyField(to=UniqueContentRule, blank=False)
 
     class Meta: