Fixes #12639 - Make sure name expansions throws a validation error on decrementing ranges (#13326)

* Fixes #12639 - Make sure name expansions throws a validation error on decrementing ranges

* Fix pep8

* Also fail on equal start & end values

---------

Co-authored-by: Jeremy Stretch <jstretch@netboxlabs.com>

netbox/dcim/forms/object_create.py

@@ -52,7 +52,10 @@ class ComponentCreateForm(forms.Form):
         super().clean()
 
         # Validate that all replication fields generate an equal number of values
-        pattern_count = len(self.cleaned_data[self.replication_fields[0]])
+        if not (patterns := self.cleaned_data.get(self.replication_fields[0])):
+            return
+
+        pattern_count = len(patterns)
         for field_name in self.replication_fields:
             value_count = len(self.cleaned_data[field_name])
             if self.cleaned_data[field_name] and value_count != pattern_count:

netbox/utilities/forms/utils.py

@@ -60,6 +60,9 @@ def parse_alphanumeric_range(string):
         except ValueError:
             begin, end = dash_range, dash_range
         if begin.isdigit() and end.isdigit():
+            if int(begin) >= int(end):
+                raise forms.ValidationError(f'Range "{dash_range}" is invalid.')
+
             for n in list(range(int(begin), int(end) + 1)):
                 values.append(n)
         else:
@@ -71,6 +74,10 @@ def parse_alphanumeric_range(string):
                 # Not a valid range (more than a single character)
                 if not len(begin) == len(end) == 1:
                     raise forms.ValidationError(f'Range "{dash_range}" is invalid.')
+
+                if ord(begin) >= ord(end):
+                    raise forms.ValidationError(f'Range "{dash_range}" is invalid.')
+
                 for n in list(range(ord(begin), ord(end) + 1)):
                     values.append(chr(n))
     return values

netbox/utilities/tests/test_forms.py

@@ -264,8 +264,9 @@ class ExpandAlphanumeric(TestCase):
         self.assertEqual(sorted(expand_alphanumeric_pattern('r[a-9]a')), [])
 
     def test_invalid_range_bounds(self):
-        self.assertEqual(sorted(expand_alphanumeric_pattern('r[9-8]a')), [])
-        self.assertEqual(sorted(expand_alphanumeric_pattern('r[b-a]a')), [])
+        with self.assertRaises(forms.ValidationError):
+            sorted(expand_alphanumeric_pattern('r[9-8]a'))
+            sorted(expand_alphanumeric_pattern('r[b-a]a'))
 
     def test_invalid_range_len(self):
         with self.assertRaises(forms.ValidationError):