Prevent duplicate groups in reference format fields (#4291)

InvenTree/InvenTree/format.py

@@ -16,11 +16,21 @@ def parse_format_string(fmt_string: str) -> dict:
 
     info = {}
 
+    seen_groups = set()
+
     for group in groups:
         # Skip any group which does not have a named value
         if not group[1]:
             continue
 
+        name = group[1]
+
+        # Check for duplicate named groups
+        if name in seen_groups:
+            raise ValueError(f"Duplicate group '{name}'")
+        else:
+            seen_groups.add(name)
+
         info[group[1]] = {
             'format': group[1],
             'prefix': group[0],

InvenTree/InvenTree/models.py

@@ -233,9 +233,9 @@ class ReferenceIndexingMixin(models.Model):
 
         try:
             info = InvenTree.format.parse_format_string(pattern)
-        except Exception:
+        except Exception as exc:
             raise ValidationError({
-                "value": _("Improperly formatted pattern"),
+                "value": _("Improperly formatted pattern") + ": " + str(exc)
             })
 
         # Check that only 'allowed' keys are provided