Add server-side annotation for "can_build" (#7619)

* Add server-side annotation for "can_build"

- This calculation now performed on the server (in the API)
- Allows better table ordering, etc
- Makes it available for data export

* Bump API version

src/backend/InvenTree/InvenTree/api_version.py

@@ -1,12 +1,15 @@
 """InvenTree API version information."""
 
 # InvenTree API version
-INVENTREE_API_VERSION = 217
+INVENTREE_API_VERSION = 218
 
 """Increment this API version number whenever there is a significant change to the API that any clients need to know about."""
 
 
 INVENTREE_API_TEXT = """
+v218 - 2024-07-11 : https://github.com/inventree/InvenTree/pull/7619
+    - Adds "can_build" field to the BomItem API
+
 v217 - 2024-07-09 : https://github.com/inventree/InvenTree/pull/7599
     - Fixes bug in "project_code" field for order API endpoints
 

src/backend/InvenTree/part/api.py

@@ -1841,7 +1841,6 @@ class BomList(BomMixin, DataExportViewMixin, ListCreateDestroyAPIView):
     """
 
     filterset_class = BomFilter
-
     filter_backends = SEARCH_ORDER_FILTER_ALIAS
 
     search_fields = [
@@ -1855,6 +1854,7 @@ class BomList(BomMixin, DataExportViewMixin, ListCreateDestroyAPIView):
     ]
 
     ordering_fields = [
+        'can_build',
         'quantity',
         'sub_part',
         'available_stock',

src/backend/InvenTree/part/serializers.py

@@ -1506,6 +1506,8 @@ class BomItemSerializer(
             'on_order',
             # Annotated field describing quantity being built
             'building',
+            # Annotate the total potential quantity we can build
+            'can_build',
         ]
 
     def __init__(self, *args, **kwargs):
@@ -1560,6 +1562,8 @@ class BomItemSerializer(
 
     building = serializers.FloatField(label=_('In Production'), read_only=True)
 
+    can_build = serializers.FloatField(label=_('Can Build'), read_only=True)
+
     # Cached pricing fields
     pricing_min = InvenTree.serializers.InvenTreeMoneySerializer(
         source='sub_part.pricing_data.overall_min', allow_null=True, read_only=True
@@ -1733,6 +1737,20 @@ class BomItemSerializer(
             )
         )
 
+        # Annotate the "can_build" quantity
+        queryset = queryset.alias(
+            total_stock=ExpressionWrapper(
+                F('available_variant_stock')
+                + F('available_substitute_stock')
+                + F('available_stock'),
+                output_field=FloatField(),
+            )
+        ).annotate(
+            can_build=ExpressionWrapper(
+                F('total_stock') / F('quantity'), output_field=FloatField()
+            )
+        )
+
         return queryset