🐛(backend) prevent owner from leaving a soft-deleted document

Owners could leave trashed documents via the leave endpoint, deleting
their `DocumentAccess` and all subtree access. When the last owner
leaves a document it creates an orphan as no owners remains in the doc.

Signed-off-by: BOUKERFA Mohamed El Amine <boukerfa.ma@gmail.com>

CHANGELOG.md

@@ -24,6 +24,7 @@ and this project adheres to
 
 ### Fixed
 
+- 🐛(backend) prevent owner from leaving a soft-deleted document
 - 🐛(frontend) fix removed item in the tree #2420
 - 🐛(frontend) fix service worker causing reload on tab focus #2454
 

src/backend/core/models.py

@@ -1326,11 +1326,15 @@ class Document(MP_Node, BaseModel):
         ) and not is_deleted
 
         # compute can_leave
-        # A user can leave a document if it has non privileged role on the document or it has
-        # access to it with a link_trace
-        can_leave = user.is_authenticated and (
-            (has_access_role and not is_owner_or_admin)
-            or (not has_access_role and self.has_link_trace(user))
+        # An authenticated user can leave a document if it has a non
+        # privileged role on the document or access to it with a link_trace
+        can_leave = (
+            user.is_authenticated
+            and not is_deleted
+            and (
+                (has_access_role and not is_owner_or_admin)
+                or (not has_access_role and self.has_link_trace(user))
+            )
         )
 
         link_select_options = LinkReachChoices.get_select_options(

src/backend/core/tests/documents/test_api_documents_leave.py

@@ -183,6 +183,39 @@ def test_api_documents_leave_connected_access_with_privileged_role_not_allowed(
     assert models.DocumentAccess.objects.count() == 5
 
 
+@pytest.mark.parametrize(
+    "link_reach",
+    models.LinkReachChoices.values,
+)
+def test_api_documents_leave_connected_owner_on_deleted_document_not_allowed(
+    link_reach,
+):
+    """
+    An owner can not leave a soft-deleted document, even when it also has a link_trace.
+    """
+    user = factories.UserFactory()
+
+    document = factories.DocumentFactory(
+        link_reach=link_reach,
+        link_traces=[user],
+        users=[(user, models.RoleChoices.OWNER)],
+    )
+    document.soft_delete()
+
+    assert models.DocumentAccess.objects.filter(document=document, user=user).exists()
+    assert models.LinkTrace.objects.filter(document=document, user=user).exists()
+
+    client = APIClient()
+    client.force_login(user)
+    response = client.post(f"/api/v1.0/documents/{document.id!s}/leave/")
+
+    assert response.status_code == status.HTTP_403_FORBIDDEN
+
+    # The owner kept its access and link_trace: it did not leave the trashed document.
+    assert models.DocumentAccess.objects.filter(document=document, user=user).exists()
+    assert models.LinkTrace.objects.filter(document=document, user=user).exists()
+
+
 @pytest.mark.parametrize(
     "link_reach",
     models.LinkReachChoices.values,