From 4f266958e3310b635b670dddfb3581584a19c8e1 Mon Sep 17 00:00:00 2001
From: Oliver Walters <oliver.henry.walters@gmail.com>
Date: Mon, 17 Feb 2020 22:11:44 +1100
Subject: [PATCH] Add custom migration

- Required to initialize the MPTT fields for the StockItem model
---
 InvenTree/stock/admin.py                      |  7 +++++++
 .../migrations/0022_auto_20200217_1109.py     | 21 +++++++++++++++++++
 InvenTree/stock/models.py                     |  7 +++++++
 3 files changed, 35 insertions(+)
 create mode 100644 InvenTree/stock/migrations/0022_auto_20200217_1109.py

diff --git a/InvenTree/stock/admin.py b/InvenTree/stock/admin.py
index c33010bf3b..8c91518de0 100644
--- a/InvenTree/stock/admin.py
+++ b/InvenTree/stock/admin.py
@@ -85,6 +85,13 @@ class StockItemResource(ModelResource):
     
     stocktake_date = Field(attribute='stocktake_date', widget=widgets.DateWidget())
 
+    def after_import(self, dataset, result, using_transactions, dry_run, **kwargs):
+
+        super().after_import(dataset, result, using_transactions, dry_run, **kwargs)
+
+        # Rebuild the StockItem tree(s)
+        StockItem.objects.rebuild()
+
     class Meta:
         model = StockItem
         skip_unchanged = True
diff --git a/InvenTree/stock/migrations/0022_auto_20200217_1109.py b/InvenTree/stock/migrations/0022_auto_20200217_1109.py
new file mode 100644
index 0000000000..0db3985361
--- /dev/null
+++ b/InvenTree/stock/migrations/0022_auto_20200217_1109.py
@@ -0,0 +1,21 @@
+# Generated by Django 2.2.9 on 2020-02-17 11:09
+
+from django.db import migrations
+from stock import models
+
+
+def update_stock_item_tree(apps, schema_editor):
+    # Update the StockItem MPTT model
+
+    models.StockItem.objects.rebuild()
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('stock', '0021_auto_20200215_2232'),
+    ]
+
+    operations = [
+        migrations.RunPython(update_stock_item_tree)
+    ]
diff --git a/InvenTree/stock/models.py b/InvenTree/stock/models.py
index e9e237b779..dcea62a4bb 100644
--- a/InvenTree/stock/models.py
+++ b/InvenTree/stock/models.py
@@ -385,6 +385,13 @@ class StockItem(MPTTModel):
 
         return True
 
+    @property
+    def child_count(self):
+        """ Return the number of 'child' items associated with this StockItem.
+        A child item is one which has been split from this one.
+        """
+        return self.get_descendants(include_self=False).count()
+
     @property
     def in_stock(self):