Extend ObjectChange to optionally indicate a related object (e.g. a parent device)

netbox/extras/models.py

@@ -665,7 +665,9 @@ class ReportResult(models.Model):
 @python_2_unicode_compatible
 class ObjectChange(models.Model):
     """
-    Record a change to an object and the user account associated with that change.
+    Record a change to an object and the user account associated with that change. A change record may optionally
+    indicate an object related to the one being changed. For example, a change to an interface may also indicate the
+    parent device. This will ensure changes made to component models appear in the parent model's changelog.
     """
     time = models.DateTimeField(
         auto_now_add=True,
@@ -688,14 +690,30 @@ class ObjectChange(models.Model):
     action = models.PositiveSmallIntegerField(
         choices=OBJECTCHANGE_ACTION_CHOICES
     )
-    content_type = models.ForeignKey(
+    changed_object_type = models.ForeignKey(
         to=ContentType,
-        on_delete=models.CASCADE
+        on_delete=models.PROTECT,
+        related_name='+'
     )
-    object_id = models.PositiveIntegerField()
+    changed_object_id = models.PositiveIntegerField()
     changed_object = GenericForeignKey(
-        ct_field='content_type',
-        fk_field='object_id'
+        ct_field='changed_object_type',
+        fk_field='changed_object_id'
+    )
+    related_object_type = models.ForeignKey(
+        to=ContentType,
+        on_delete=models.PROTECT,
+        related_name='+',
+        blank=True,
+        null=True
+    )
+    related_object_id = models.PositiveIntegerField(
+        blank=True,
+        null=True
+    )
+    related_object = GenericForeignKey(
+        ct_field='related_object_type',
+        fk_field='related_object_id'
     )
     object_repr = models.CharField(
         max_length=200,
@@ -706,14 +724,17 @@ class ObjectChange(models.Model):
     )
 
     serializer = 'extras.api.serializers.ObjectChangeSerializer'
-    csv_headers = ['time', 'user', 'request_id', 'action', 'content_type', 'object_id', 'object_repr', 'object_data']
+    csv_headers = [
+        'time', 'user', 'user_name', 'request_id', 'action', 'changed_object_type', 'changed_object_id',
+        'related_object_type', 'related_object_id', 'object_repr', 'object_data',
+    ]
 
     class Meta:
         ordering = ['-time']
 
     def __str__(self):
         return '{} {} {} by {}'.format(
-            self.content_type,
+            self.changed_object_type,
             self.object_repr,
             self.get_action_display().lower(),
             self.user_name
@@ -722,8 +743,7 @@ class ObjectChange(models.Model):
     def save(self, *args, **kwargs):
 
         # Record the user's name and the object's representation as static strings
-        if self.user is not None:
-            self.user_name = self.user.username
+        self.user_name = self.user.username
         self.object_repr = str(self.changed_object)
 
         return super(ObjectChange, self).save(*args, **kwargs)
@@ -734,11 +754,14 @@ class ObjectChange(models.Model):
     def to_csv(self):
         return (
             self.time,
-            self.user or self.user_name,
+            self.user,
+            self.user_name,
             self.request_id,
             self.get_action_display(),
-            self.content_type,
-            self.object_id,
+            self.changed_object_type,
+            self.changed_object_id,
+            self.related_object_type,
+            self.related_object_id,
             self.object_repr,
             self.object_data,
         )