Fix a regression in migration 0056

Having more than one collection version in the system prevents the
migration 0056 to run, because null as a value is not allowed to appear
more than once.

We need to clean this up very careful, becuase on some systems the
migration may have applied cleanly.

fixes pulp#2040

CHANGES/240.bugfix

@@ -0,0 +1 @@
+Fixed a regression with migration 0056 failing on multiple null values on a unique constraint.

pulp_ansible/app/migrations/0056_collectionversion_sha256.py

@@ -16,8 +16,4 @@ class Migration(migrations.Migration):
             field=models.CharField(default='', max_length=64, null=True),
             preserve_default=False,
         ),
-        migrations.AlterUniqueTogether(
-            name="collectionversion",
-            unique_together={("sha256",), ("namespace", "name", "version")},
-        ),
     ]

pulp_ansible/app/migrations/0058_fix_0056_regression.py

@@ -0,0 +1,30 @@
+# Generated by Django 4.2.16 on 2024-11-22 12:06
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("ansible", "0057_collectionversion_sha256_migrate"),
+    ]
+
+    operations = [
+        # ---------------------------------------------------------------------
+        # In the current timeline of migrations, this step seems superfluous.
+        # But in version 0.23.0 we shipped a bad version of 0056.
+        # This repairs it.
+        migrations.AlterUniqueTogether(
+            name="collectionversion",
+            unique_together={("namespace", "name", "version")},
+        ),
+        # ---------------------------------------------------------------------
+        migrations.AddConstraint(
+            model_name="collectionversion",
+            constraint=models.UniqueConstraint(
+                condition=models.Q(("sha256__isnull", False)),
+                fields=("sha256",),
+                name="unique_sha256",
+            ),
+        ),
+    ]

pulp_ansible/app/models.py

@@ -236,13 +236,18 @@ def __str__(self):
 
     class Meta:
         default_related_name = "%(app_label)s_%(model_name)s"
-        unique_together = (("namespace", "name", "version"), ("sha256",))
+        unique_together = (("namespace", "name", "version"),)
         constraints = [
+            UniqueConstraint(
+                fields=("sha256",),
+                name="unique_sha256",
+                condition=Q(sha256__isnull=False),
+            ),
             UniqueConstraint(
                 fields=("collection", "is_highest"),
                 name="unique_is_highest",
                 condition=Q(is_highest=True),
-            )
+            ),
         ]
 
 

pulp_ansible/tests/unit/migrations/test_0057_collection_version_sha256_migrate.py

@@ -7,33 +7,49 @@ def test_collection_version_sha256_migrate(migrate):
     Collection = apps.get_model("ansible", "Collection")
     CollectionVersion = apps.get_model("ansible", "CollectionVersion")
 
-    artifact = Artifact.objects.create(
-        size=8, sha256="SENTINEL", file=SimpleUploadedFile("foo", b"deadbeef")
+    collection = Collection.objects.create(namespace="snap", name="crackle")
+
+    # Create two collection versions, because `sha256=null` can violate the uniquenes constraint.
+    artifact1 = Artifact.objects.create(
+        size=8, sha256="SENTINEL1", file=SimpleUploadedFile("foo", b"deadbeef")
     )
-    collection = Collection.objects.create(
+    cv1 = CollectionVersion.objects.create(
+        pulp_type="collection_version",
+        collection=collection,
         namespace="snap",
         name="crackle",
+        version="1.0.0",
+        version_minor="1",
+        version_major="0",
+        version_patch="0",
     )
-    cv = CollectionVersion.objects.create(
+    cv1.contentartifact_set.create(artifact=artifact1)
+
+    artifact2 = Artifact.objects.create(
+        size=8, sha256="SENTINEL2", file=SimpleUploadedFile("foo", b"beefdead")
+    )
+    cv2 = CollectionVersion.objects.create(
         pulp_type="collection_version",
         collection=collection,
         namespace="snap",
         name="crackle",
-        version="pop",
-        version_minor="1",
-        version_major="2",
-        version_patch="3",
+        version="2.0.0",
+        version_minor="2",
+        version_major="0",
+        version_patch="0",
     )
-    cv.contentartifact_set.create(artifact=artifact)
+    cv2.contentartifact_set.create(artifact=artifact2)
 
     apps = migrate([("ansible", "0056_collectionversion_sha256")])
     CollectionVersion = apps.get_model("ansible", "CollectionVersion")
 
-    cv = CollectionVersion.objects.get(pk=cv.pk)
-    assert cv.sha256 == ""
+    cv1 = CollectionVersion.objects.get(pk=cv1.pk)
+    assert cv1.sha256 == ""
 
     apps = migrate([("ansible", "0057_collectionversion_sha256_migrate")])
     CollectionVersion = apps.get_model("ansible", "CollectionVersion")
 
-    cv = CollectionVersion.objects.get(pk=cv.pk)
-    assert cv.sha256 == "SENTINEL"
+    cv1 = CollectionVersion.objects.get(pk=cv1.pk)
+    assert cv1.sha256 == "SENTINEL1"
+
+    apps = migrate([("ansible", "0058_fix_0056_regression")])