Show UPC for receiving line item if no product reference

to help with troubleshooting invoice file parsing etc.

tailbone/views/purchasing/receiving.py

@@ -1479,6 +1479,14 @@ class ReceivingBatchView(PurchasingBatchView):
         super(ReceivingBatchView, self).configure_row_form(f)
         batch = self.get_instance()
 
+        # when viewing a row which has no product reference, enable
+        # the 'upc' field to help with troubleshooting
+        # TODO: this maybe should be optional..?
+        if self.viewing and 'upc' not in f:
+            row = self.get_row_instance()
+            if not row.product:
+                f.append('upc')
+
         # allow input for certain fields only; all others are readonly
         mutable = [
             'invoice_unit_cost',