Merge #2601

2601: Fix creation of deep structures using import in update mode r=mergify[bot] a=ghostwheel42

## What type of PR?

bug-fix

## What does this PR do?

Fixes creation of deep structures (ie user with fetch) when using config-import in update mode.

### Related issue(s)

- closes #2493

## Prerequisites

Before we can consider review and merge, please make sure the following list is done and checked.
If an entry in not applicable, you can check it or remove it from the list.

- [ ] In case of feature or enhancement: documentation updated accordingly
- [ ] Unless it's docs or a minor change: add [changelog](https://mailu.io/master/contributors/workflow.html#changelog) entry file.


Co-authored-by: Alexander Graf <ghostwheel42@users.noreply.github.com>

core/admin/mailu/schemas.py

@@ -909,7 +909,9 @@ class BaseSchema(ma.SQLAlchemyAutoSchema, Storage):
         # stabilize import of auto-increment primary keys (not required),
         # by matching import data to existing items and setting primary key
         if not self._primary in data:
-            for item in getattr(self.recall('parent'), self.recall('field', 'parent')):
+            parent = self.recall('parent')
+            if parent is not None:
+                for item in getattr(parent, self.recall('field', 'parent')):
                     existing = self.dump(item, many=False)
                     this = existing.pop(self._primary)
                     if data == existing:
@@ -919,6 +921,11 @@ class BaseSchema(ma.SQLAlchemyAutoSchema, Storage):
 
         # try to load instance
         instance = self.instance or self.get_instance(data)
+
+        # remember instance as parent for pruning siblings
+        if not self.Meta.sibling and self.context.get('update'):
+            self.store('parent', instance)
+
         if instance is None:
 
             if '__delete__' in data:
@@ -931,9 +938,6 @@ class BaseSchema(ma.SQLAlchemyAutoSchema, Storage):
         else:
 
             if self.context.get('update'):
-                # remember instance as parent for pruning siblings
-                if not self.Meta.sibling:
-                    self.store('parent', instance)
                 # delete instance from session when marked
                 if '__delete__' in data:
                     self.opts.sqla_session.delete(instance)
@@ -1014,8 +1018,10 @@ class BaseSchema(ma.SQLAlchemyAutoSchema, Storage):
                 del_items = True
 
         if add_items or del_items:
+            parent = self.recall('parent')
+            if parent is not None:
                 existing = {item[self._primary] for item in items if self._primary in item}
-            for item in getattr(self.recall('parent'), self.recall('field', 'parent')):
+                for item in getattr(parent, self.recall('field', 'parent')):
                     key = getattr(item, self._primary)
                     if key not in existing:
                         if add_items:

towncrier/newsfragments/2601.bugfix

@@ -0,0 +1 @@
+Fix creation of deep structures using import in update mode