Fix Singleton and ThreadLocalSingleton to handle initialization errors

src/dependency_injector/providers.pyx

@@ -2182,9 +2182,14 @@ cdef class BaseSingleton(Provider):
         raise NotImplementedError()
 
     def _async_init_instance(self, future_result, result):
-        instance = result.result()
+        try:
-        self.__storage = instance
+            instance = result.result()
-        future_result.set_result(instance)
+        except Exception as exception:
+            self.__storage = None
+            future_result.set_exception(exception)
+        else:
+            self.__storage = instance
+            future_result.set_result(instance)
 
 
 cdef class Singleton(BaseSingleton):
@@ -2407,9 +2412,14 @@ cdef class ThreadLocalSingleton(BaseSingleton):
             return instance
 
     def _async_init_instance(self, future_result, result):
-        instance = result.result()
+        try:
-        self.__storage.instance = instance
+            instance = result.result()
-        future_result.set_result(instance)
+        except Exception as exception:
+            del self.__storage.instance
+            future_result.set_exception(exception)
+        else:
+            self.__storage.instance = instance
+            future_result.set_result(instance)
 
 
 cdef class DelegatedThreadLocalSingleton(ThreadLocalSingleton):

tests/unit/providers/test_async_py36.py

@@ -329,6 +329,37 @@ class SingletonTests(AsyncTestCase):
         self.assertIs(instance1, instance2)
         self.assertIs(instance, instance)
 
+    def test_async_init_with_error(self):
+        # Disable default exception handling to prevent output
+        asyncio.get_event_loop().set_exception_handler(lambda loop, context: ...)
+
+        async def create_instance():
+            create_instance.counter += 1
+            raise RuntimeError()
+
+        create_instance.counter = 0
+
+        provider = providers.Singleton(create_instance)
+
+
+        future = provider()
+        self.assertTrue(provider.is_async_mode_enabled())
+
+        with self.assertRaises(RuntimeError):
+            self._run(future)
+
+        self.assertEqual(create_instance.counter, 1)
+        self.assertTrue(provider.is_async_mode_enabled())
+
+        with self.assertRaises(RuntimeError):
+            self._run(provider())
+
+        self.assertEqual(create_instance.counter, 2)
+        self.assertTrue(provider.is_async_mode_enabled())
+
+        # Restore default exception handling
+        asyncio.get_event_loop().set_exception_handler(None)
+
 
 class DelegatedSingletonTests(AsyncTestCase):
 
@@ -398,6 +429,36 @@ class ThreadLocalSingletonTests(AsyncTestCase):
         self.assertIs(instance, instance)
 
 
+    def test_async_init_with_error(self):
+        # Disable default exception handling to prevent output
+        asyncio.get_event_loop().set_exception_handler(lambda loop, context: ...)
+
+        async def create_instance():
+            create_instance.counter += 1
+            raise RuntimeError()
+        create_instance.counter = 0
+
+        provider = providers.ThreadLocalSingleton(create_instance)
+
+        future = provider()
+        self.assertTrue(provider.is_async_mode_enabled())
+
+        with self.assertRaises(RuntimeError):
+            self._run(future)
+
+        self.assertEqual(create_instance.counter, 1)
+        self.assertTrue(provider.is_async_mode_enabled())
+
+        with self.assertRaises(RuntimeError):
+            self._run(provider())
+
+        self.assertEqual(create_instance.counter, 2)
+        self.assertTrue(provider.is_async_mode_enabled())
+
+        # Restore default exception handling
+        asyncio.get_event_loop().set_exception_handler(None)
+
+
 class DelegatedThreadLocalSingletonTests(AsyncTestCase):
 
     def test_async_mode(self):

tests/unit/providers/test_resource_py35.py

@@ -447,6 +447,7 @@ class AsyncResourceTest(AsyncTestCase):
 
         future = provider()
         self.assertTrue(provider.initialized)
+        self.assertTrue(provider.is_async_mode_enabled())
 
         # Disable default exception handling to prevent output
         asyncio.get_event_loop().set_exception_handler(lambda loop, context: ...)
@@ -458,6 +459,7 @@ class AsyncResourceTest(AsyncTestCase):
         asyncio.get_event_loop().set_exception_handler(None)
 
         self.assertFalse(provider.initialized)
+        self.assertTrue(provider.is_async_mode_enabled())
 
     def test_init_and_shutdown_methods(self):
         async def _init():