Part: Extend logic for "latest" serial number

- Return value if it is a string
- Remove 'getNextSerialNumber' function
- Improve functionality of function which returns serial number placeholder string

InvenTree/stock/tests.py

@@ -372,14 +372,14 @@ class VariantTest(StockTest):
 
         self.assertFalse(chair.checkIfSerialNumberExists(30))
 
-        self.assertEqual(chair.getNextSerialNumber(), 23)
+        self.assertEqual(chair.getLatestSerialNumber(), '22')
 
         # Same operations on a sub-item
         variant = Part.objects.get(pk=10003)
-        self.assertEqual(variant.getNextSerialNumber(), 23)
+        self.assertEqual(variant.getLatestSerialNumber(), '22')
 
         # Create a new serial number
-        n = variant.getHighestSerialNumber()
+        n = variant.getLatestSerialNumber()
 
         item = StockItem(
             part=variant,
@@ -394,10 +394,8 @@ class VariantTest(StockTest):
         # Verify items with a non-numeric serial don't offer a next serial.
         item.serial = "string"
         item.save()
-        self.assertEqual(variant.getNextSerialNumber(), None)
 
-        # And the same for the range when serializing.
-        self.assertEqual(variant.getSerialNumberString(5), None)
+        self.assertEqual(variant.getLatestSerialNumber(), "string")
 
         # This should pass, although not strictly an int field now.
         item.serial = int(n) + 1

InvenTree/stock/views.py

@@ -1234,8 +1234,9 @@ class StockItemCreate(AjaxCreateView):
         part = self.get_part(form=form)
 
         if part is not None:
-            sn = part.getNextSerialNumber()
-            form.field_placeholder['serial_numbers'] = _('Next available serial number is') + ' ' + str(sn)
+
+            # Add placeholder text for the serial number field
+            form.field_placeholder['serial_numbers'] = part.getSerialNumberString()
 
             form.rebuild_layout()
 
@@ -1353,11 +1354,6 @@ class StockItemCreate(AjaxCreateView):
                 part = Part.objects.get(id=part_id)
                 quantity = Decimal(form['quantity'].value())
 
-                sn = part.getNextSerialNumber()
-                form.field_placeholder['serial_numbers'] = _("Next available serial number is") + " " + str(sn)
-
-                form.rebuild_layout()
-
             except (Part.DoesNotExist, ValueError, InvalidOperation):
                 part = None
                 quantity = 1