From 36bfd2ed58c6bf9d95366ac397402b01eb346669 Mon Sep 17 00:00:00 2001
From: Roman Mogylatov <rmogilatov@gmail.com>
Date: Mon, 23 Aug 2021 20:54:17 -0400
Subject: [PATCH] Improve resource subclasses typing and make shutdown
 definition optional (#492)

* Improve resource subclasses typing and make shutdown definition optional

* Update mypy tests
---
 src/dependency_injector/resources.py       | 12 ++++-----
 tests/typing/resource.py                   |  6 ++---
 tests/unit/providers/test_resource_py35.py | 29 ++++++++--------------
 3 files changed, 18 insertions(+), 29 deletions(-)

diff --git a/src/dependency_injector/resources.py b/src/dependency_injector/resources.py
index efa6b15e..2468fd7a 100644
--- a/src/dependency_injector/resources.py
+++ b/src/dependency_injector/resources.py
@@ -1,7 +1,7 @@
 """Resources module."""
 
 import abc
-from typing import TypeVar, Generic
+from typing import TypeVar, Generic, Optional
 
 
 T = TypeVar('T')
@@ -10,20 +10,18 @@ T = TypeVar('T')
 class Resource(Generic[T], metaclass=abc.ABCMeta):
 
     @abc.abstractmethod
-    def init(self, *args, **kwargs) -> T:
+    def init(self, *args, **kwargs) -> Optional[T]:
         ...
 
-    @abc.abstractmethod
-    def shutdown(self, resource: T) -> None:
+    def shutdown(self, resource: Optional[T]) -> None:
         ...
 
 
 class AsyncResource(Generic[T], metaclass=abc.ABCMeta):
 
     @abc.abstractmethod
-    async def init(self, *args, **kwargs) -> T:
+    async def init(self, *args, **kwargs) -> Optional[T]:
         ...
 
-    @abc.abstractmethod
-    async def shutdown(self, resource: T) -> None:
+    async def shutdown(self, resource: Optional[T]) -> None:
         ...
diff --git a/tests/typing/resource.py b/tests/typing/resource.py
index b5687451..b468df42 100644
--- a/tests/typing/resource.py
+++ b/tests/typing/resource.py
@@ -1,4 +1,4 @@
-from typing import List, Iterator, Generator, AsyncIterator, AsyncGenerator
+from typing import List, Iterator, Generator, AsyncIterator, AsyncGenerator, Optional
 
 from dependency_injector import providers, resources
 
@@ -35,7 +35,7 @@ class MyResource4(resources.Resource[List[int]]):
     def init(self, *args, **kwargs) -> List[int]:
         return []
 
-    def shutdown(self, resource: List[int]) -> None:
+    def shutdown(self, resource: Optional[List[int]]) -> None:
         ...
 
 
@@ -87,7 +87,7 @@ class MyResource8(resources.AsyncResource[List[int]]):
     async def init(self, *args, **kwargs) -> List[int]:
         return []
 
-    async def shutdown(self, resource: List[int]) -> None:
+    async def shutdown(self, resource: Optional[List[int]]) -> None:
         ...
 
 
diff --git a/tests/unit/providers/test_resource_py35.py b/tests/unit/providers/test_resource_py35.py
index 2a38881e..ae8074b3 100644
--- a/tests/unit/providers/test_resource_py35.py
+++ b/tests/unit/providers/test_resource_py35.py
@@ -1,6 +1,7 @@
 """Dependency injector resource provider unit tests."""
 
 import asyncio
+import inspect
 import unittest
 from typing import Any
 
@@ -158,7 +159,7 @@ class ResourceTests(unittest.TestCase):
 
         self.assertTrue(issubclass(TestResource, resources.Resource))
 
-    def test_init_class_abc_definition_is_required(self):
+    def test_init_class_abc_init_definition_is_required(self):
         class TestResource(resources.Resource):
             ...
 
@@ -166,19 +167,13 @@ class ResourceTests(unittest.TestCase):
             TestResource()
 
         self.assertIn("Can't instantiate abstract class TestResource", str(context.exception))
-        self.assertIn("init, shutdown", str(context.exception))
+        self.assertIn("init", str(context.exception))
 
-
-    def test_init_class_abc_shutdown_definition_is_required(self):
+    def test_init_class_abc_shutdown_definition_is_not_required(self):
         class TestResource(resources.Resource):
             def init(self):
                 ...
-
-        with self.assertRaises(TypeError) as context:
-            TestResource()
-
-        self.assertIn("Can't instantiate abstract class TestResource", str(context.exception))
-        self.assertIn("shutdown", str(context.exception))
+        self.assertTrue(hasattr(TestResource(), 'shutdown'))
 
     def test_init_not_callable(self):
         provider = providers.Resource(1)
@@ -497,7 +492,7 @@ class AsyncResourceTest(AsyncTestCase):
 
         self.assertTrue(issubclass(TestAsyncResource, resources.AsyncResource))
 
-    def test_init_async_class_abc_definition_is_required(self):
+    def test_init_async_class_abc_init_definition_is_required(self):
         class TestAsyncResource(resources.AsyncResource):
             ...
 
@@ -505,18 +500,14 @@ class AsyncResourceTest(AsyncTestCase):
             TestAsyncResource()
 
         self.assertIn("Can't instantiate abstract class TestAsyncResource", str(context.exception))
-        self.assertIn("init, shutdown", str(context.exception))
+        self.assertIn("init", str(context.exception))
 
-    def test_init_async_class_abc_shutdown_definition_is_required(self):
+    def test_init_async_class_abc_shutdown_definition_is_not_required(self):
         class TestAsyncResource(resources.AsyncResource):
             async def init(self):
                 ...
-
-        with self.assertRaises(TypeError) as context:
-            TestAsyncResource()
-
-        self.assertIn("Can't instantiate abstract class TestAsyncResource", str(context.exception))
-        self.assertIn("shutdown", str(context.exception))
+        self.assertTrue(hasattr(TestAsyncResource(), 'shutdown'))
+        self.assertTrue(inspect.iscoroutinefunction(TestAsyncResource.shutdown))
 
     def test_init_with_error(self):
         async def _init():