708 - Add Natural Key Support to Tag model.

CHANGELOG.rst

@@ -10,6 +10,7 @@ Changelog
   We believe that this should not cause a noticable performance change, and the number of queries involved should not change.
 * Add Django 5.0 support (no code changes were needed, but now we test this release).
 * Add Python 3.12 support
+* Add Support for dumpdata/loaddata using Natural Keys
 
 5.0.1 (2023-10-26)
 ~~~~~~~~~~~~~~~~~~

taggit/models.py

@@ -1,3 +1,5 @@
+from typing import List
+
 from django.conf import settings
 from django.contrib.contenttypes.fields import GenericForeignKey
 from django.contrib.contenttypes.models import ContentType
@@ -15,7 +17,29 @@
         return tag
 
 
-class TagBase(models.Model):
+class NaturalKeyManager(models.Manager):
+    def __init__(self, natural_key_fields: List[str], *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.natural_key_fields = natural_key_fields
+
+    def get_by_natural_key(self, *args):
+        if len(args) != len(self.model.natural_key_fields):
+            raise ValueError(
+                "Number of arguments does not match number of natural key fields."
+            )
+        lookup_kwargs = dict(zip(self.model.natural_key_fields, args))
+        return self.get(**lookup_kwargs)
+
+
+class NaturalKeyModel(models.Model):
+    def natural_key(self):
+        return (getattr(self, field) for field in self.natural_key_fields)
+
+    class Meta:
+        abstract = True
+
+
+class TagBase(NaturalKeyModel):
     name = models.CharField(
         verbose_name=pgettext_lazy("A tag name", "name"), unique=True, max_length=100
     )
@@ -26,6 +50,9 @@
         allow_unicode=True,
     )
 
+    natural_key_fields = ["name"]
+    objects = NaturalKeyManager(natural_key_fields)
+
     def __str__(self):
         return self.name
 
@@ -91,13 +118,15 @@
         app_label = "taggit"
 
 
-class ItemBase(models.Model):
+class ItemBase(NaturalKeyModel):
     def __str__(self):
         return gettext("%(object)s tagged with %(tag)s") % {
             "object": self.content_object,
             "tag": self.tag,
         }
 
+    objects = NaturalKeyManager(natural_key_fields=["name"])
+
     class Meta:
         abstract = True
 
@@ -170,13 +199,15 @@
 
 class GenericTaggedItemBase(CommonGenericTaggedItemBase):
     object_id = models.IntegerField(verbose_name=_("object ID"), db_index=True)
+    natural_key_fields = ["object_id"]
 
     class Meta:
         abstract = True
 
 
 class GenericUUIDTaggedItemBase(CommonGenericTaggedItemBase):
     object_id = models.UUIDField(verbose_name=_("object ID"), db_index=True)
+    natural_key_fields = ["object_id"]
 
     class Meta:
         abstract = True

tests/tests.py

@@ -1,3 +1,4 @@
+import os
 from io import StringIO
 from unittest import mock
 
@@ -1398,3 +1399,100 @@ def test_tests_have_no_pending_migrations(self):
         out = StringIO()
         call_command("makemigrations", "tests", dry_run=True, stdout=out)
         self.assertEqual(out.getvalue().strip(), "No changes detected in app 'tests'")
+
+
+class NaturalKeyTests(TestCase):
+    @classmethod
+    def setUpTestData(cls):
+        cls.tag_names = ["circle", "square", "triangle", "rectangle", "pentagon"]
+        cls.filename = "test_data_dump.json"
+        cls.tag_count = len(cls.tag_names)
+
+    def setUp(self):
+        self.tags = self._create_tags()
+
+    def tearDown(self):
+        self._clear_existing_tags()
+        try:
+            os.remove(self.filename)
+        except FileNotFoundError:
+            pass
+
+    @property
+    def _queryset(self):
+        return Tag.objects.filter(name__in=self.tag_names)
+
+    def _create_tags(self):
+        return Tag.objects.bulk_create(
+            [Tag(name=shape, slug=shape) for shape in self.tag_names],
+            ignore_conflicts=True,
+        )
+
+    def _clear_existing_tags(self):
+        self._queryset.delete()
+
+    def _dump_model(self, model):
+        model_label = model._meta.label
+        with open(self.filename, "w") as f:
+            call_command(
+                "dumpdata",
+                model_label,
+                natural_primary=True,
+                use_natural_foreign_keys=True,
+                stdout=f,
+            )
+
+    def _load_model(self):
+        call_command("loaddata", self.filename)
+
+    def test_tag_natural_key(self):
+        """
+        Test that tags can be dumped and loaded using natural keys.
+        """
+
+        # confirm count in the DB
+        self.assertEqual(self._queryset.count(), self.tag_count)
+
+        # dump all tags to a file
+        self._dump_model(Tag)
+
+        # Delete all tags
+        self._clear_existing_tags()
+
+        # confirm all tags clear
+        self.assertEqual(self._queryset.count(), 0)
+
+        # load the tags from the file
+        self._load_model()
+
+        # confirm count in the DB
+        self.assertEqual(self._queryset.count(), self.tag_count)
+
+    def test_tag_reloading_with_changed_pk(self):
+        """Test that tags are not reliant on the primary key of the tag model.
+
+        Test that data is correctly loaded after database state has changed.
+
+        """
+        original_shape = self._queryset.first()
+        original_pk = original_shape.pk
+        original_shape_name = original_shape.name
+        new_shape_name = "hexagon"
+
+        # dump all tags to a file
+        self._dump_model(Tag)
+
+        # Delete the tag
+        self._clear_existing_tags()
+
+        # create new tag with the same PK
+        Tag.objects.create(name=new_shape_name, slug=new_shape_name, pk=original_pk)
+
+        # Load the tags from the file
+        self._load_model()
+
+        # confirm that load did not overwrite the new_shape
+        self.assertEqual(Tag.objects.get(pk=original_pk).name, new_shape_name)
+
+        # confirm that the original shape was reloaded with a different PK
+        self.assertNotEqual(Tag.objects.get(name=original_shape_name).pk, original_pk)