Allow Zero Quantity BOM Item with System Setting (#11437)

* allow zero qty bom item with setting

* add allow zero bom qty setting to docs

---------

Co-authored-by: Oliver <oliver.henry.walters@gmail.com>

src/backend/InvenTree/common/setting/system.py

@@ -637,6 +637,14 @@ SYSTEM_SETTINGS: dict[str, InvenTreeSettingsKeyType] = {
         'default': False,
         'validator': bool,
     },
+    'PART_BOM_ALLOW_ZERO_QUANTITY': {
+        'name': _('Allow BOM Zero Quantity'),
+        'description': _(
+            'Accept a zero quantity for BOM item for part. Enables using setup quantity to define a quantity required per build, independent of build quantity'
+        ),
+        'default': False,
+        'validator': bool,
+    },
     'LABEL_ENABLE': {
         'name': _('Enable label printing'),
         'description': _('Enable label printing from the web interface'),

src/backend/InvenTree/part/serializers.py

@@ -22,6 +22,7 @@ from sql_util.utils import SubqueryCount
 
 import common.currency
 import common.filters
+import common.models
 import common.serializers
 import company.models
 import InvenTree.helpers
@@ -1656,8 +1657,20 @@ class BomItemSerializer(
 
     def validate_quantity(self, quantity):
         """Perform validation for the BomItem quantity field."""
-        if quantity <= 0:
-            raise serializers.ValidationError(_('Quantity must be greater than zero'))
+        allow_zero_qty = common.models.InvenTreeSetting.get_setting(
+            'PART_BOM_ALLOW_ZERO_QUANTITY', False
+        )
+
+        if allow_zero_qty:
+            if quantity < 0:
+                raise serializers.ValidationError(
+                    _('Quantity must be greater than or equal to zero')
+                )
+        else:
+            if quantity <= 0:
+                raise serializers.ValidationError(
+                    _('Quantity must be greater than zero')
+                )
 
         return quantity
 

src/frontend/src/pages/Index/Settings/SystemSettings.tsx

@@ -217,6 +217,7 @@ export default function SystemSettings() {
               'PART_SALABLE',
               'PART_VIRTUAL',
               'PART_COPY_BOM',
+              'PART_BOM_ALLOW_ZERO_QUANTITY',
               'PART_COPY_PARAMETERS',
               'PART_COPY_TESTS',
               'PART_CATEGORY_PARAMETERS',