From 3e92aa9fe778509f8c653c4f1a8ab293c569e597 Mon Sep 17 00:00:00 2001
From: Jeremy Stretch <jstretch@digitalocean.com>
Date: Thu, 8 Nov 2018 12:15:56 -0500
Subject: [PATCH] Fixes #2571: Enforce deletion of attached cable when deleting
 a termination point

---
 CHANGELOG.md                     |  1 +
 netbox/dcim/models.py            | 12 ++++++++
 netbox/dcim/signals.py           | 10 ++++---
 netbox/dcim/tests/test_models.py | 51 ++++++++++++++++++++++++++++++++
 4 files changed, 70 insertions(+), 4 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d40cc01fd..49fdc6b04 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -43,6 +43,7 @@ NetBox now supports modeling physical cables for console, power, and interface c
 * [#2566](https://github.com/digitalocean/netbox/issues/2566) - Prevent both ends of a cable from connecting to the same termination point
 * [#2567](https://github.com/digitalocean/netbox/issues/2567) - Introduced proxy models to represent console/power/interface connections
 * [#2569](https://github.com/digitalocean/netbox/issues/2569) - Added LSH fiber type; removed SC duplex/simplex designations
+* [#2571](https://github.com/digitalocean/netbox/issues/2571) - Enforce deletion of attached cable when deleting a termination point
 
 ## API Changes
 
diff --git a/netbox/dcim/models.py b/netbox/dcim/models.py
index 22a830123..d3c18d7e2 100644
--- a/netbox/dcim/models.py
+++ b/netbox/dcim/models.py
@@ -73,6 +73,18 @@ class CableTermination(models.Model):
         null=True
     )
 
+    # Generic relations to Cable. These ensure that an attached Cable is deleted if the terminated object is deleted.
+    _cabled_as_a = GenericRelation(
+        to='dcim.Cable',
+        content_type_field='termination_a_type',
+        object_id_field='termination_a_id'
+    )
+    _cabled_as_b = GenericRelation(
+        to='dcim.Cable',
+        content_type_field='termination_b_type',
+        object_id_field='termination_b_id'
+    )
+
     class Meta:
         abstract = True
 
diff --git a/netbox/dcim/signals.py b/netbox/dcim/signals.py
index b37c34226..0bb6690b4 100644
--- a/netbox/dcim/signals.py
+++ b/netbox/dcim/signals.py
@@ -45,10 +45,12 @@ def update_connected_endpoints(instance, **kwargs):
 def nullify_connected_endpoints(instance, **kwargs):
 
     # Disassociate the Cable from its termination points
-    instance.termination_a.cable = None
-    instance.termination_a.save()
-    instance.termination_b.cable = None
-    instance.termination_b.save()
+    if instance.termination_a is not None:
+        instance.termination_a.cable = None
+        instance.termination_a.save()
+    if instance.termination_b is not None:
+        instance.termination_b.cable = None
+        instance.termination_b.save()
 
     # If this Cable was part of a complete path, tear it down
     endpoint_a, endpoint_b = instance.get_path_endpoints()
diff --git a/netbox/dcim/tests/test_models.py b/netbox/dcim/tests/test_models.py
index 012c7d121..d2072812c 100644
--- a/netbox/dcim/tests/test_models.py
+++ b/netbox/dcim/tests/test_models.py
@@ -149,3 +149,54 @@ class RackTestCase(TestCase):
             face=None,
         )
         self.assertTrue(pdu)
+
+
+class CableTestCase(TestCase):
+
+    def setUp(self):
+
+        site = Site.objects.create(name='Test Site 1', slug='test-site-1')
+        manufacturer = Manufacturer.objects.create(name='Test Manufacturer 1', slug='test-manufacturer-1')
+        devicetype = DeviceType.objects.create(
+            manufacturer=manufacturer, model='Test Device Type 1', slug='test-device-type-1'
+        )
+        devicerole = DeviceRole.objects.create(
+            name='Test Device Role 1', slug='test-device-role-1', color='ff0000'
+        )
+        self.device1 = Device.objects.create(
+            device_type=devicetype, device_role=devicerole, name='TestDevice1', site=site
+        )
+        self.device2 = Device.objects.create(
+            device_type=devicetype, device_role=devicerole, name='TestDevice2', site=site
+        )
+        self.interface1 = Interface.objects.create(device=self.device1, name='eth0')
+        self.interface2 = Interface.objects.create(device=self.device2, name='eth0')
+        self.cable = Cable(termination_a=self.interface1, termination_b=self.interface2)
+        self.cable.save()
+
+    def test_cable_creation(self):
+        """
+        When a new Cable is created, it must be cached on either termination point.
+        """
+        interface1 = Interface.objects.get(pk=self.interface1.pk)
+        self.assertEqual(self.cable.termination_a, interface1)
+        interface2 = Interface.objects.get(pk=self.interface2.pk)
+        self.assertEqual(self.cable.termination_b, interface2)
+
+    def test_cable_deletion(self):
+        """
+        When a Cable is deleted, the `cable` field on its termination points must be nullified.
+        """
+        self.cable.delete()
+        interface1 = Interface.objects.get(pk=self.interface1.pk)
+        self.assertIsNone(interface1.cable)
+        interface2 = Interface.objects.get(pk=self.interface2.pk)
+        self.assertIsNone(interface2.cable)
+
+    def test_cabletermination_deletion(self):
+        """
+        When a CableTermination object is deleted, its attached Cable (if any) must also be deleted.
+        """
+        self.interface1.delete()
+        cable = Cable.objects.filter(pk=self.cable.pk).first()
+        self.assertIsNone(cable)