From 92ac93aac54c23dc9a0e3980da13481fa1f0f101 Mon Sep 17 00:00:00 2001
From: Oliver Walters <oliver.henry.walters@gmail.com>
Date: Tue, 18 Aug 2020 14:17:59 +1000
Subject: [PATCH] More intelligent checking for circular BOM

- Check all the way down a BOM "tree"
- Validate BOM tree before allowing BOM submission
---
 InvenTree/part/models.py | 54 ++++++++++++++++++++++++++++------------
 InvenTree/part/views.py  | 10 +++++++-
 2 files changed, 47 insertions(+), 17 deletions(-)

diff --git a/InvenTree/part/models.py b/InvenTree/part/models.py
index cbc22c5605..dd126d5730 100644
--- a/InvenTree/part/models.py
+++ b/InvenTree/part/models.py
@@ -271,6 +271,42 @@ class Part(MPTTModel):
     def __str__(self):
         return "{n} - {d}".format(n=self.full_name, d=self.description)
 
+    def checkAddToBOM(self, parent):
+        """
+        Check if this Part can be added to the BOM of another part.
+
+        This will fail if:
+
+        a) The parent part is the same as this one
+        b) The parent part is used in the BOM for *this* part
+        c) The parent part is used in the BOM for any child parts under this one
+        
+        Failing this check raises a ValidationError!
+
+        """
+
+        if parent is None:
+            return
+
+        if self.pk == parent.pk:
+            raise ValidationError({'sub_part': _("Part '{p1}' is  used in BOM for '{p2}' (recursive)".format(
+                p1=str(self),
+                p2=str(parent)
+            ))})
+
+        # Ensure that the parent part does not appear under any child BOM item!
+        for item in self.bom_items.all():
+
+            # Check for simple match
+            if item.sub_part == parent:
+                raise ValidationError({'sub_part': _("Part '{p1}' is  used in BOM for '{p2}' (recursive)".format(
+                    p1=str(parent),
+                    p2=str(self)
+                ))})
+
+            # And recursively check too
+            item.sub_part.checkAddToBOM(parent)
+
     def checkIfSerialNumberExists(self, sn):
         """
         Check if a serial number exists for this Part.
@@ -1474,22 +1510,8 @@ class BomItem(models.Model):
         except Part.DoesNotExist:
             pass
 
-        # A part cannot refer to itself in its BOM
-        try:
-            if self.sub_part is not None and self.part is not None:
-                if self.part == self.sub_part:
-                    raise ValidationError({'sub_part': _('Part cannot be added to its own Bill of Materials')})
-        
-            # TODO - Make sure that there is no recusion
-
-            # Test for simple recursion
-            for item in self.sub_part.bom_items.all():
-                if self.part == item.sub_part:
-                    raise ValidationError({'sub_part': _("Part '{p1}' is  used in BOM for '{p2}' (recursive)".format(p1=str(self.part), p2=str(self.sub_part)))})
-        
-        except Part.DoesNotExist:
-            # A blank Part will be caught elsewhere
-            pass
+        # Check for circular BOM references
+        self.sub_part.checkAddToBOM(self.part)
 
     class Meta:
         verbose_name = _("BOM Item")
diff --git a/InvenTree/part/views.py b/InvenTree/part/views.py
index 9f35dbbb10..a01b6b4ff2 100644
--- a/InvenTree/part/views.py
+++ b/InvenTree/part/views.py
@@ -1325,8 +1325,16 @@ class BomUpload(FormView):
 
         for row in self.bom_rows:
             # Has a part been selected for the given row?
-            if row.get('part', None) is None:
+            part = row.get('part', None)
+
+            if part is None:
                 row['errors']['part'] = _('Select a part')
+            else:
+                # Will the selected part result in a recursive BOM?
+                try:
+                    part.checkAddToBOM(self.part)
+                except ValidationError:
+                    row['errors']['part'] = _('Selected part creates a circular BOM')
 
             # Has a quantity been specified?
             if row.get('quantity', None) is None: