fix(rules): allow category expressions to clear categories

app/apps/rules/tests/test_tasks.py

@@ -0,0 +1,82 @@
+from datetime import date
+from decimal import Decimal
+from unittest.mock import patch
+
+from django.contrib.auth import get_user_model
+from django.test import TransactionTestCase
+
+from apps.accounts.models import Account
+from apps.currencies.models import Currency
+from apps.rules.models import TransactionRule, UpdateOrCreateTransactionRuleAction
+from apps.rules.tasks import check_for_transaction_rules
+from apps.transactions.models import Transaction
+
+
+def run_check_for_transaction_rules_without_worker_wrapper(**kwargs):
+    task_func = check_for_transaction_rules.func
+    task_func = getattr(task_func, "__wrapped__", task_func)
+
+    return task_func(**kwargs)
+
+
+class CheckForTransactionRulesTests(TransactionTestCase):
+    def setUp(self):
+        User = get_user_model()
+        self.user = User.objects.create_user(
+            email="rules@example.com",
+            password="testpass123",
+        )
+        self.currency = Currency.objects.create(
+            code="USD",
+            name="US Dollar",
+            decimal_places=2,
+        )
+        self.account = Account.objects.create(
+            name="Main Account",
+            currency=self.currency,
+            owner=self.user,
+        )
+
+    @patch("apps.rules.signals.check_for_transaction_rules.defer")
+    def test_update_or_create_action_can_clear_category_from_none_expression(
+        self, mock_defer
+    ):
+        source_transaction = Transaction.objects.create(
+            account=self.account,
+            type=Transaction.Type.EXPENSE,
+            amount=Decimal("10.00"),
+            date=date(2026, 5, 4),
+            reference_date=date(2026, 5, 1),
+            description="Source without category",
+            category=None,
+            owner=self.user,
+        )
+        rule = TransactionRule.objects.create(
+            active=True,
+            on_create=False,
+            on_update=True,
+            name="Copy transaction",
+            trigger="True",
+            owner=self.user,
+        )
+        UpdateOrCreateTransactionRuleAction.objects.create(
+            rule=rule,
+            set_account="account_id",
+            set_type="'EX'",
+            set_date="date",
+            set_reference_date="reference_date",
+            set_amount="amount",
+            set_description="'Generated transaction'",
+            set_category="category_name",
+        )
+
+        run_check_for_transaction_rules_without_worker_wrapper(
+            instance_id=source_transaction.id,
+            user_id=self.user.id,
+            signal="transaction_updated",
+        )
+
+        generated_transaction = Transaction.objects.get(
+            description="Generated transaction"
+        )
+        self.assertIsNone(generated_transaction.category)