Fix #4149 - correct logic in RackForm

changes/4149.fixed

@@ -0,0 +1 @@
+Fixed a bug that prevented renaming a `Rack` if it contained any devices whose names were not globally unique.

nautobot/dcim/forms.py

@@ -696,21 +696,21 @@ def clean(self):
         cleaned_data = self.cleaned_data
         site = cleaned_data.get("site")
 
-        if self.instance:
+        if self.instance and site != self.instance.site:
             # If the site is changed, the rack post save signal attempts to update the rack devices,
-            # which may result in an Exception.
-            # To avoid an unhandled exception in signal, catch this error here.
-            duplicate_devices_names = (
-                Device.objects.values_list("name", flat=True)
-                .annotate(name_count=Count("name"))
-                .filter(name_count__gt=1)
-            )
-            duplicate_devices = Device.objects.filter(site=site, name__in=list(duplicate_devices_names)).values_list(
-                "name", flat=True
-            )
+            # which may result in an Exception if the updated devices conflict with existing devices at this site.
+            # To avoid an unhandled exception in the signal, check for this scenario here.
+            duplicate_devices = set()
+            for device in self.instance.devices.all():
+                qs = Device.objects.exclude(pk=device.pk).filter(site=site, tenant=device.tenant, name=device.name)
+                if qs.exists():
+                    duplicate_devices.add(qs.first().name)
             if duplicate_devices:
                 raise ValidationError(
-                    {"site": f"Device with `name` in {list(duplicate_devices)} and site={site} already exists."}
+                    {
+                        "site": f"Device(s) {sorted(duplicate_devices)} already exist in site {site} and "
+                        "would conflict with same-named devices in this rack."
+                    }
                 )
         return cleaned_data
 

nautobot/dcim/tests/test_forms.py

@@ -444,5 +444,21 @@ def test_update_rack_site(self):
         form = RackForm(data=data, instance=racks[0])
         self.assertEqual(
             str(form.errors.as_data()["site"][0]),
-            str(["Device with `name` in ['device1'] and site=Site-2 already exists."]),
+            str(
+                [
+                    "Device(s) ['device1'] already exist in site Site-2 and "
+                    "would conflict with same-named devices in this rack."
+                ]
+            ),
         )
+
+        # Check for https://github.com/nautobot/nautobot/issues/4149
+        data = {
+            "name": "New name",
+            "site": racks[0].site.pk,
+            "status": racks[0].status.pk,
+            "u_height": 48,
+            "width": RackWidthChoices.WIDTH_19IN,
+        }
+        form = RackForm(data=data, instance=racks[0])
+        self.assertTrue(form.is_valid())