From 47f3994f933ddede4521a4981adbf92e72b4482d Mon Sep 17 00:00:00 2001
From: Daniel Sheppard <dans@dansheps.com>
Date: Sun, 2 Jun 2024 22:06:34 -0500
Subject: [PATCH] Catch AssertionError from cable trace and throw
 ValidationError

---
 netbox/dcim/models/cables.py                | 21 +++++++++++++--------
 netbox/netbox/views/generic/object_views.py |  7 +++++++
 2 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/netbox/dcim/models/cables.py b/netbox/dcim/models/cables.py
index 64f0b8560..e9b58e413 100644
--- a/netbox/dcim/models/cables.py
+++ b/netbox/dcim/models/cables.py
@@ -237,7 +237,10 @@ class Cable(PrimaryModel):
                 if not termination.pk or termination not in b_terminations:
                     CableTermination(cable=self, cable_end='B', termination=termination).save()
 
-        trace_paths.send(Cable, instance=self, created=_created)
+        try:
+            trace_paths.send(Cable, instance=self, created=_created)
+        except ValidationError as e:
+            raise ValidationError(f'{e}')
 
     def get_status_color(self):
         return LinkStatusChoices.colors.get(self.status)
@@ -532,7 +535,8 @@ class CablePath(models.Model):
 
         # Ensure all originating terminations are attached to the same link
         if len(terminations) > 1:
-            assert all(t.link == terminations[0].link for t in terminations[1:])
+            assert all(t.link == terminations[0].link for t in terminations[1:]), \
+                "All originating terminations must start must be attached to the same link"
 
         path = []
         position_stack = []
@@ -543,12 +547,13 @@ class CablePath(models.Model):
         while terminations:
 
             # Terminations must all be of the same type
-            assert all(isinstance(t, type(terminations[0])) for t in terminations[1:])
+            assert all(isinstance(t, type(terminations[0])) for t in terminations[1:]), \
+                "All mid-span terminations must have the same termination type"
 
             # All mid-span terminations must all be attached to the same device
             if not isinstance(terminations[0], PathEndpoint):
-                assert all(isinstance(t, type(terminations[0])) for t in terminations[1:])
-                assert all(t.parent_object == terminations[0].parent_object for t in terminations[1:])
+                assert all(t.parent_object == terminations[0].parent_object for t in terminations[1:]), \
+                    "All mid-span terminations must have the same parent object"
 
             # Check for a split path (e.g. rear port fanning out to multiple front ports with
             # different cables attached)
@@ -571,8 +576,8 @@ class CablePath(models.Model):
                     return None
                 # Otherwise, halt the trace if no link exists
                 break
-            assert all(type(link) in (Cable, WirelessLink) for link in links)
-            assert all(isinstance(link, type(links[0])) for link in links)
+            assert all(type(link) in (Cable, WirelessLink) for link in links), "All links must be cable or wireless"
+            assert all(isinstance(link, type(links[0])) for link in links), "All links must match first link type"
 
             # Step 3: Record asymmetric paths as split
             not_connected_terminations = [termination.link for termination in terminations if termination.link is None]
@@ -656,7 +661,7 @@ class CablePath(models.Model):
                     for rt in remote_terminations:
                         position = positions.pop()
                         q_filter |= Q(rear_port_id=rt.pk, rear_port_position=position)
-                    assert q_filter is not Q()
+                    assert q_filter is not Q(), "Remote termination query filter is empty, please open a bug report"
                     front_ports = FrontPort.objects.filter(q_filter)
                 # Obtain the individual front ports based on the termination and position
                 elif position_stack:
diff --git a/netbox/netbox/views/generic/object_views.py b/netbox/netbox/views/generic/object_views.py
index 243ae2547..5335a974e 100644
--- a/netbox/netbox/views/generic/object_views.py
+++ b/netbox/netbox/views/generic/object_views.py
@@ -3,6 +3,7 @@ from collections import defaultdict
 from copy import deepcopy
 
 from django.contrib import messages
+from django.core.exceptions import ValidationError
 from django.db import router, transaction
 from django.db.models import ProtectedError, RestrictedError
 from django.db.models.deletion import Collector
@@ -307,6 +308,12 @@ class ObjectEditView(GetReturnURLMixin, BaseObjectView):
                 form.add_error(None, e.message)
                 clear_events.send(sender=self)
 
+            # Catch any validation errors thrown in the model.save() or form.save() methods
+            except ValidationError as e:
+                logger.debug(e.message)
+                form.add_error(None, e.message)
+                clear_events.send(sender=self)
+
         else:
             logger.debug("Form validation failed")