Bug fix for allocating items to build (#6532)

* Bug fix for allocating items to build

- Handle case where allocated quantity is less than 1
- Add unit tests
- Closes https://github.com/inventree/InvenTree/issues/6145

* Remove debug messgae

InvenTree/build/serializers.py

@@ -920,18 +920,24 @@ class BuildAllocationSerializer(serializers.Serializer):
                 if build_line.bom_item.consumable:
                     continue
 
+                params = {
+                    "build_line": build_line,
+                    "stock_item": stock_item,
+                    "install_into": output,
+                }
+
                 try:
-                    # Create a new BuildItem to allocate stock
+                    if build_item := BuildItem.objects.filter(**params).first():
-                    build_item, created = BuildItem.objects.get_or_create(
+                        # Find an existing BuildItem for this stock item
-                        build_line=build_line,
+                        # If it exists, increase the quantity
-                        stock_item=stock_item,
-                        install_into=output,
-                    )
-                    if created:
-                        build_item.quantity = quantity
-                    else:
                         build_item.quantity += quantity
-                    build_item.save()
+                        build_item.save()
+                    else:
+                        # Create a new BuildItem to allocate stock
+                        build_item = BuildItem.objects.create(
+                            quantity=quantity,
+                            **params
+                        )
                 except (ValidationError, DjangoValidationError) as exc:
                     # Catch model errors and re-throw as DRF errors
                     raise ValidationError(detail=serializers.as_serializer_error(exc))

InvenTree/build/test_api.py

@@ -822,6 +822,58 @@ class BuildAllocationTest(BuildAPITest):
         allocation.refresh_from_db()
         self.assertEqual(allocation.quantity, 5000)
 
+    def test_fractional_allocation(self):
+        """Test allocation of a fractional quantity of stock items.
+
+        Ref: https://github.com/inventree/InvenTree/issues/6508
+        """
+
+        si = StockItem.objects.get(pk=2)
+
+        # Find line item
+        line = self.build.build_lines.all().filter(bom_item__sub_part=si.part).first()
+
+        # Test a fractional quantity when the *available* quantity is greater than 1
+        si.quantity = 100
+        si.save()
+
+        response = self.post(
+            self.url,
+            {
+                "items": [
+                    {
+                        "build_line": line.pk,
+                        "stock_item": si.pk,
+                        "quantity": 0.1616,
+                    }
+                ]
+            },
+            expected_code=201
+        )
+
+        # Test a fractional quantity when the *available* quantity is less than 1
+        si = StockItem.objects.create(
+            part=si.part,
+            quantity=0.3159,
+            tree_id=0,
+            level=0,
+            lft=0, rght=0
+        )
+
+        response = self.post(
+            self.url,
+            {
+                "items": [
+                    {
+                        "build_line": line.pk,
+                        "stock_item": si.pk,
+                        "quantity": 0.1616,
+                    }
+                ]
+            },
+            expected_code=201,
+        )
+
 
 class BuildOverallocationTest(BuildAPITest):
     """Unit tests for over allocation of stock items against a build order.