[bug] Fix part duplicate checks (#12574)

* [bug] Fix part duplicate checks

* Additional unit tests

src/backend/InvenTree/part/models.py

@@ -1053,11 +1053,20 @@ class Part(
             raise ValidationError(_('Duplicate part revision already exists.'))
 
         # Ensure unique across (Name, revision, IPN) (as specified)
-        if (self.revision or self.IPN) and (
-            Part.objects
-            .exclude(pk=self.pk)
-            .filter(name=self.name, revision=self.revision, IPN=self.IPN)
-            .exists()
+        # Note: the 'unique_part' database constraint only rejects a row when
+        # *all three* fields are non-null (Postgres treats NULL as distinct from
+        # NULL), so mirror that here rather than skipping whenever either field
+        # is merely blank - an empty string ('') still collides with another
+        # empty string at the database level, unlike None/NULL.
+        if (
+            self.IPN is not None
+            and self.revision is not None
+            and (
+                Part.objects
+                .exclude(pk=self.pk)
+                .filter(name=self.name, revision=self.revision, IPN=self.IPN)
+                .exists()
+            )
         ):
             raise ValidationError(
                 _('Part with this Name, IPN and Revision already exists.')

src/backend/InvenTree/part/test_api.py

@@ -1638,6 +1638,36 @@ class PartCreationTests(PartAPITestBase):
         self.assertFalse(response.data['active'])
         self.assertFalse(response.data['purchaseable'])
 
+    def test_create_duplicate_no_ipn_revision(self):
+        """Test that creating a duplicate part (same name, no IPN/revision) returns a 400.
+
+        Regression test for a bug where the duplicate-name check was skipped
+        whenever IPN and revision were both blank, letting the request fall
+        through to an unhandled database IntegrityError (500) instead of a
+        proper validation error (400).
+        """
+        url = reverse('api-part-list')
+
+        data = {
+            'name': 'TEST1',
+            'category': 1,
+            'assembly': True,
+            'component': True,
+            'consumable': False,
+            'is_template': False,
+            'purchaseable': False,
+            'salable': False,
+            'testable': False,
+            'trackable': False,
+            'virtual': False,
+        }
+
+        self.post(url, data, expected_code=201)
+
+        # Attempting to create the exact same part again must be rejected cleanly
+        response = self.post(url, data, expected_code=400)
+        self.assertIn('non_field_errors', response.data)
+
     def test_notes_on_create(self):
         """Test that notes can be set when creating a Part."""
         list_url = reverse('api-part-list')

src/backend/InvenTree/part/test_part.py

@@ -219,6 +219,40 @@ class PartTest(TestCase):
         with self.assertRaises(ValidationError):
             part_2.validate_unique()
 
+    def test_duplicate_no_ipn_revision(self):
+        """Test that we cannot create a duplicate Part when IPN and revision are both blank strings.
+
+        Regression test: the underlying 'unique_part' database constraint treats
+        blank IPN/revision values (empty strings, as sent by the API when these
+        fields are omitted) as equal, so validate_unique() must catch this case
+        too, rather than raising an unhandled IntegrityError. Note that this is
+        distinct from *unset* (None/NULL) values, which the database constraint
+        does *not* treat as colliding (see test_revisions).
+        """
+        cat = PartCategory.objects.get(pk=1)
+
+        Part.objects.create(
+            category=cat,
+            name='dupe_test',
+            description='description',
+            IPN='',
+            revision='',
+        )
+
+        part = Part(
+            category=cat,
+            name='dupe_test',
+            description='description',
+            IPN='',
+            revision='',
+        )
+
+        with self.assertRaises(ValidationError):
+            part.validate_unique()
+
+        with self.assertRaises(ValidationError):
+            part.save()
+
     def test_attributes(self):
         """Test Part attributes."""
         self.assertEqual(self.r1.name, 'R_2K2_0805')