Fix validation of duplicate IPN

- Duplicate IPN check does not apply if an empty IPN value is set
- Note that "if x" is a more pythonic test than "if x not in [None, '']"

InvenTree/part/models.py

@@ -777,7 +777,8 @@ class Part(MPTTModel):
         # User can decide whether duplicate IPN (Internal Part Number) values are allowed
         allow_duplicate_ipn = common.models.InvenTreeSetting.get_setting('PART_ALLOW_DUPLICATE_IPN')
 
-        if self.IPN is not None and not allow_duplicate_ipn:
+        # Raise an error if an IPN is set, and it is a duplicate
+        if self.IPN and not allow_duplicate_ipn:
             parts = Part.objects.filter(IPN__iexact=self.IPN)
             parts = parts.exclude(pk=self.pk)
 
@@ -798,6 +799,10 @@ class Part(MPTTModel):
 
         super().clean()
 
+        # Strip IPN field
+        if self.IPN:
+            self.IPN = self.IPN.strip()
+
         if self.trackable:
             for part in self.get_used_in().all():
 

InvenTree/stock/models.py

@@ -453,10 +453,12 @@ class StockItem(MPTTModel):
 
         super().clean()
 
-        if self.serial is not None and type(self.serial) is str:
+        # Strip serial number field
+        if self.serial:
             self.serial = self.serial.strip()
 
-        if self.batch is not None and type(self.batch) is str:
+        # Strip batch code field
+        if self.batch:
             self.batch = self.batch.strip()
 
         try: