Create initial migration file

InvenTree/stock/migrations/0064_auto_20210621_1724.py

@@ -0,0 +1,41 @@
+# Generated by Django 3.2.4 on 2021-06-21 07:24
+
+from django.db import migrations
+
+
+def extract_purchase_price(apps, schema_editor):
+    """
+    Find instances of StockItem which do *not* have a purchase price set,
+    but which point to a PurchaseOrder where there *is* a purchase price set.
+
+    Then, assign *that* purchase price to original StockItem.
+
+    This is to address an issue where older versions of InvenTree
+    did not correctly copy purchase price information cross to the StockItem objects.
+
+    Current InvenTree version (as of 2021-06-21) copy this information across correctly,
+    so this one-time data migration should suffice.
+    """
+
+    # Required database models
+    StockItem = apps.get_model('stock', 'stockitem')
+    PurchaseOrder = apps.get_model('order', 'purchaseorder')
+    Part = apps.get_model('part', 'part')
+
+
+def reverse_operation(apps, schema_editor):
+    """
+    DO NOTHING!
+    """
+    pass
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('stock', '0063_auto_20210511_2343'),
+    ]
+
+    operations = [
+        migrations.RunPython(extract_purchase_price, reverse_code=reverse_operation)
+    ]