Simplify subrepo deletion

fixes: #3345

CHANGES/3345.misc

@@ -0,0 +1 @@
+Simplified subrepo deletion logic to make it more reliable.

pulp_rpm/app/migrations/0058_alter_addon_repository_alter_variant_repository.py

@@ -0,0 +1,33 @@
+# Generated by Django 4.2.7 on 2023-11-29 23:12
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("core", "0114_remove_task_args_remove_task_kwargs"),
+        ("rpm", "0057_rpmpublication_checksum_type_and_more"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="addon",
+            name="repository",
+            field=models.ForeignKey(
+                on_delete=django.db.models.deletion.RESTRICT,
+                related_name="addons",
+                to="core.repository",
+            ),
+        ),
+        migrations.AlterField(
+            model_name="variant",
+            name="repository",
+            field=models.ForeignKey(
+                null=True,
+                on_delete=django.db.models.deletion.RESTRICT,
+                related_name="variants",
+                to="core.repository",
+            ),
+        ),
+    ]

pulp_rpm/app/models/distribution.py

@@ -2,7 +2,7 @@
 from logging import getLogger
 
 from django.db import models
-from django.db.models.signals import post_delete
+from django.db.models.signals import pre_delete
 from django.dispatch import receiver
 
 from pulpcore.plugin.models import (
@@ -107,8 +107,8 @@ def repositories(self):
         """
         from pulp_rpm.app.models import RpmRepository
 
-        repo_ids = list(self.addons.values_list("repository__pk", flat=True))
-        repo_ids += list(self.variants.values_list("repository__pk", flat=True))
+        repo_ids = list(self.addons.values_list("repository_id", flat=True))
+        repo_ids += list(self.variants.values_list("repository_id", flat=True))
         return RpmRepository.objects.filter(pk__in=repo_ids)
 
     def content(self):
@@ -255,7 +255,7 @@ class Addon(BaseModel):
     distribution_tree = models.ForeignKey(
         DistributionTree, on_delete=models.CASCADE, related_name="addons"
     )
-    repository = models.ForeignKey(Repository, on_delete=models.PROTECT, related_name="addons")
+    repository = models.ForeignKey(Repository, on_delete=models.RESTRICT, related_name="addons")
 
     class Meta:
         unique_together = (
@@ -317,7 +317,7 @@ class Variant(BaseModel):
         DistributionTree, on_delete=models.CASCADE, related_name="variants"
     )
     repository = models.ForeignKey(
-        Repository, on_delete=models.PROTECT, related_name="variants", null=True
+        Repository, on_delete=models.RESTRICT, related_name="variants", null=True
     )
 
     class Meta:
@@ -331,19 +331,10 @@ class Meta:
         )
 
 
-@receiver(post_delete, sender=Addon)
-@receiver(post_delete, sender=Variant)
+@receiver(pre_delete, sender=DistributionTree)
 def cleanup_subrepos(sender, instance, **kwargs):
     """
     Remove subrepos when a DistributionTree is being removed.
-
     """
-    subrepo = None
-    try:
-        subrepo = instance.repository
-    except Repository.DoesNotExist:
-        pass
-    if subrepo:
-        Variant.objects.filter(repository=subrepo).delete()
-        Addon.objects.filter(repository=subrepo).delete()
-        subrepo.delete()
+    repos = instance.repositories()
+    repos.delete()