fix: Regression that broke sync callbacks interacting with Django ORM. Closes #446 (#452)

Author: fgmacedo

docs/releases/2.3.2.md

@@ -43,6 +43,9 @@ See {ref}`listeners` for more details.
 
 ## Bugfixes in 2.3.2
 
+- Fixes [#446](https://github.com/fgmacedo/python-statemachine/issues/446): Regression that broke sync callbacks
+  interacting with Django ORM due to the added async support and
+  [Django's async safety guards](https://docs.djangoproject.com/en/5.1/topics/async/#async-safety).
 - Fixes [#449](https://github.com/fgmacedo/python-statemachine/issues/449): Regression that did not trigger events
   in nested calls within an already running transition.
 

statemachine/signature.py

@@ -7,6 +7,13 @@
 from types import MethodType
 from typing import Any
 
+try:
+    # Compatibility with Django ORM
+    # https://docs.djangoproject.com/en/5.1/topics/async/#async-safety
+    from asgiref.sync import sync_to_async
+except ImportError:  # pragma: no cover
+    sync_to_async = None  # type: ignore[assignment]
+
 
 def _make_key(method):
     method = method.func if isinstance(method, partial) else method
@@ -52,7 +59,12 @@ def wrap(cls, method):
 
         metadata_to_copy = method.func if isinstance(method, partial) else method
 
-        if iscoroutinefunction(method):
+        is_coroutine = iscoroutinefunction(method)
+        if not is_coroutine and sync_to_async is not None:
+            method = sync_to_async(method)
+            is_coroutine = True
+
+        if is_coroutine:
 
             async def method_wrapper(*args: Any, **kwargs: Any) -> Any:
                 ba = sig_bind_expected(*args, **kwargs)

tests/conftest.py

@@ -1,6 +1,7 @@
 import sys
 from datetime import datetime
 from typing import List
+from unittest.mock import patch
 
 import pytest
 
@@ -197,3 +198,9 @@ def retry(self):
             return self.model
 
     return ApprovalMachine
+
+
+@pytest.fixture(autouse=True, scope="module")
+def _mock_sync_to_async():
+    with patch("statemachine.signature.sync_to_async", None):
+        yield

tests/django_project/core/settings.py

@@ -18,7 +18,10 @@
 DATABASES = {
     "default": {
         "ENGINE": "django.db.backends.sqlite3",
-        "NAME": ":memory:",
+        "NAME": BASE_DIR / "db.sqlite3",
+        "TEST": {
+            "NAME": "testdb.sqlite3",
+        },
     }
 }
 

tests/django_project/workflow/tests.py

@@ -4,10 +4,15 @@
 from workflow.statemachines import WorfklowStateMachine
 
 pytestmark = [
-    pytest.mark.django_db,
+    pytest.mark.django_db(transaction=True),
 ]
 
 
+@pytest.fixture(autouse=True, scope="module")
+def _mock_sync_to_async():
+    """Override the mock so the sync callbacks are decorated with sync_to_async"""
+
+
 @pytest.fixture()
 def Workflow():
     from workflow.models import Workflow
@@ -39,7 +44,6 @@ def test_two(self, one):
         with pytest.raises(TransitionNotAllowed):
             wf.send("publish")
 
-    @pytest.mark.xfail(reason="This test is a regression on 2.3.0+ due to asyncio support.")
     def test_async_with_db_operation(self, one, User, Workflow):
         """Regression test for https://github.com/fgmacedo/python-statemachine/issues/446"""
 
@@ -52,5 +56,6 @@ def test_async_with_db_operation(self, one, User, Workflow):
 
         # And clear model cache, casing user to be loaded later on
         one = Workflow.objects.get(pk=one.pk)
+
         wf = WorfklowStateMachine(one)
         wf.send("notify_user")