From 82840b05902ed9982f213d91f0049309161b195d Mon Sep 17 00:00:00 2001
From: Oliver <oliver.henry.walters@gmail.com>
Date: Thu, 10 Mar 2022 15:01:20 +1100
Subject: [PATCH] Adds custom delete routine for PartCategory model

---
 InvenTree/part/models.py  | 52 ++++++++++++++++++++++-----------------
 InvenTree/stock/models.py |  2 +-
 2 files changed, 31 insertions(+), 23 deletions(-)

diff --git a/InvenTree/part/models.py b/InvenTree/part/models.py
index fc09dcd042..d9788f5fd9 100644
--- a/InvenTree/part/models.py
+++ b/InvenTree/part/models.py
@@ -20,7 +20,7 @@ from django.db.models.functions import Coalesce
 from django.core.validators import MinValueValidator
 
 from django.contrib.auth.models import User
-from django.db.models.signals import pre_delete, post_save
+from django.db.models.signals import post_save
 from django.dispatch import receiver
 
 from jinja2 import Template
@@ -76,6 +76,35 @@ class PartCategory(InvenTreeTree):
         default_keywords: Default keywords for parts created in this category
     """
 
+    def delete(self, *args, **kwargs):
+        """
+        Custom model deletion routine, which updates any child categories or parts.
+        This must be handled within a transaction.atomic(), otherwise the tree structure is damaged
+        """
+
+        with transaction.atomic():
+
+            parent = self.parent
+            tree_id = self.tree_id
+
+            # Update each part in this category to point to the parent category
+            for part in self.parts.all():
+                part.category = self.parent
+                part.save()
+
+            # Update each child category
+            for child in self.children.all():
+                child.parent = self.parent
+                child.save()
+
+            super().delete(*args, **kwargs)
+
+            if parent is not None:
+                # Partially rebuild the tree (cheaper than a complete rebuild)
+                PartCategory.objects.partial_rebuild(tree_id)
+            else:
+                PartCategory.objects.rebuild()
+
     default_location = TreeForeignKey(
         'stock.StockLocation', related_name="default_categories",
         null=True, blank=True,
@@ -260,27 +289,6 @@ class PartCategory(InvenTreeTree):
             ).delete()
 
 
-@receiver(pre_delete, sender=PartCategory, dispatch_uid='partcategory_delete_log')
-def before_delete_part_category(sender, instance, using, **kwargs):
-    """ Receives before_delete signal for PartCategory object
-
-    Before deleting, update child Part and PartCategory objects:
-
-    - For each child category, set the parent to the parent of *this* category
-    - For each part, set the 'category' to the parent of *this* category
-    """
-
-    # Update each part in this category to point to the parent category
-    for part in instance.parts.all():
-        part.category = instance.parent
-        part.save()
-
-    # Update each child category
-    for child in instance.children.all():
-        child.parent = instance.parent
-        child.save()
-
-
 def rename_part_image(instance, filename):
     """ Function for renaming a part image file
 
diff --git a/InvenTree/stock/models.py b/InvenTree/stock/models.py
index 1fa0dd1f5b..171ee7e0a3 100644
--- a/InvenTree/stock/models.py
+++ b/InvenTree/stock/models.py
@@ -65,7 +65,7 @@ class StockLocation(InvenTreeTree):
             parent = self.parent
             tree_id = self.tree_id
 
-            # Update each part in the stock location
+            # Update each stock item in the stock location
             for item in self.stock_items.all():
                 item.location = self.parent
                 item.save()