🐛(backend) prevent moving an item to itself or its descendant

[maboukerfa]

Problem

Item.move() had no guard against moving a folder into itself or one of its own descendants.

Drive uses django_ltree, which raises no error in this case, it silently runs the RawSQL path rewrite. Because the path__descendants ltree lookup (<@) is inclusive, the moved item matches its own descendant query, so both it and its children get rewritten and the subtree ends up orphaned.

Walkthrough

Screen.Recording.2026-05-22.at.12.04.08.mov

Take a parent P with path P and a child C with path P.C. Moving P into C:

old_path = self.path                      # "P"
self.path = f"{target.path}.{self.id}"     # "P.C.P"
self.save(update_fields=["path"])          # P is now "P.C.P"

# P is a FOLDER, so descendants get rewritten:
Item.objects.filter(path__descendants=old_path).update(   # descendants of "P"
    path=RawSQL("%s || subpath(path, nlevel(%s))", (self.path, old_path))
)

After self.save(), the rows matching "descendant of P" are:

• C with path P.C → P.C <@ P ✅
• P itself with its new path P.C.P → P.C.P <@ P ✅ — P matches its own descendant query

So the bulk UPDATE rewrites both, with self.path = "P.C.P" and nlevel("P") = 1:

Item	New path
C	"P.C.P" ‖ subpath("P.C", 1) = P.C.P.C
P	"P.C.P" ‖ subpath("P.C.P", 1) = P.C.P.C.P

Result: no item has path P anymore, so neither P nor C is reachable from the real tree. P ends up with the self-referential path P.C.P.C.P — a cycle baked into the materialized paths, leaving the subtree orphaned and unrecoverable through the UI.

Fix

Reject the move in Item.move() when the target is the item itself or one of its descendants, mirroring the style of the existing not-a-folder check:

if target:
    target_path = str(target.path)
    self_path = str(self.path)
    if target_path == self_path or target_path.startswith(f"{self_path}."):
        raise ValidationError(...)  # code="item_move_target_is_descendant"

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud