Small tweaks for BOM export

- Steps towards preventing circular BOMs
- Improve formatting of exported BOM

InvenTree/part/admin.py

@@ -131,11 +131,13 @@ class BomItemResource(ModelResource):
 
     level = Field(attribute='level', readonly=True)
 
-    part = Field(attribute='part', widget=widgets.ForeignKeyWidget(Part))
+    bom_id = Field(attribute='pk')
+
+    parent_part_id = Field(attribute='part', widget=widgets.ForeignKeyWidget(Part))
 
     parent_part_name = Field(attribute='part__full_name', readonly=True)
 
-    id = Field(attribute='sub_part', widget=widgets.ForeignKeyWidget(Part))
+    sub_part_id = Field(attribute='sub_part', widget=widgets.ForeignKeyWidget(Part))
 
     sub_part_name = Field(attribute='sub_part__full_name', readonly=True)
 
@@ -147,7 +149,12 @@ class BomItemResource(ModelResource):
         report_skipped = False
         clean_model_instances = True
 
-        exclude = ['checksum', ]
+        exclude = [
+            'checksum',
+            'id',
+            'part',
+            'sub_part',
+        ]
 
 
 class BomItemAdmin(ImportExportModelAdmin):

InvenTree/part/bom.py

@@ -53,12 +53,18 @@ def ExportBom(part, fmt='csv', cascade=False):
 
     bom_items = []
 
+    uids = []
+
     def add_items(items, level):
         # Add items at a given layer
         for item in items:
 
             item.level = '-' * level
 
+            # Avoid circular BOM references
+            if item.pk in uids:
+                continue
+
             bom_items.append(item)
 
             if item.sub_part.assembly: