Remove generic meta class from resource and async resource classes (#490)

* Remove generic meta class from resource and async resource classes

* Add link to the issue into the tests

* Update changelog

Author: rmk135

.coveragerc

@@ -3,5 +3,8 @@ source = src/dependency_injector
 omit = tests/unit
 plugins = Cython.Coverage
 
+[report]
+show_missing = true
+
 [html]
 directory=reports/unittests/

docs/main/changelog.rst

@@ -13,6 +13,10 @@ follows `Semantic versioning`_
   See issue `#477 <https://github.com/ets-labs/python-dependency-injector/issues/477>`_.
   Thanks to `Andrey Torsunov @gtors <https://github.com/gtors>`_  for reporting the issue.
 - Fix typing stub for ``container.override_providers()`` to accept other types besides ``Provider``.
+- Fix runtime issue with generic typing in resource initializer classes ``resources.Resource``
+  and ``resources.AsyncResource``.
+  See issue `#488 <https://github.com/ets-labs/python-dependency-injector/issues/488>`_.
+  Thanks to `@EdwardBlair <https://github.com/EdwardBlair>`_  for reporting the issue.
 
 4.35.2
 ------

src/dependency_injector/resources.py

@@ -1,26 +1,13 @@
 """Resources module."""
 
 import abc
-import sys
 from typing import TypeVar, Generic
 
-if sys.version_info < (3, 7):
-    from typing import GenericMeta
-else:
-    class GenericMeta(type):
-        ...
-
 
 T = TypeVar('T')
 
 
-class ResourceMeta(GenericMeta, abc.ABCMeta):
-    def __getitem__(cls, item):
-        # Spike for Python 3.6
-        return cls(item)
-
-
-class Resource(Generic[T], metaclass=ResourceMeta):
+class Resource(Generic[T]):
 
     @abc.abstractmethod
     def init(self, *args, **kwargs) -> T:
@@ -31,7 +18,7 @@ def shutdown(self, resource: T) -> None:
         ...
 
 
-class AsyncResource(Generic[T], metaclass=ResourceMeta):
+class AsyncResource(Generic[T]):
 
     @abc.abstractmethod
     async def init(self, *args, **kwargs) -> T:

tests/unit/providers/test_resource_py35.py

@@ -1,8 +1,8 @@
 """Dependency injector resource provider unit tests."""
 
 import asyncio
-
 import unittest
+from typing import Any
 
 from dependency_injector import containers, providers, resources, errors
 
@@ -603,3 +603,31 @@ async def _init():
 
         self.assertIs(result2, resource)
         self.assertEqual(_init.counter, 1)
+
+
+class ResourceTypingTest(unittest.TestCase):
+    # See issue: https://github.com/ets-labs/python-dependency-injector/issues/488
+
+    def test_sync_generic_type(self):
+        class MyDependency:
+            ...
+
+        class MyResource(resources.Resource[MyDependency]):
+            def init(self, *args: Any, **kwargs: Any) -> MyDependency:
+                return MyDependency()
+
+            def shutdown(self, resource: MyDependency) -> None: ...
+
+        self.assertTrue(issubclass(MyResource, resources.Resource))
+
+    def test_async_generic_type(self):
+        class MyDependency:
+            ...
+
+        class MyAsyncResource(resources.AsyncResource[MyDependency]):
+            async def init(self, *args: Any, **kwargs: Any) -> MyDependency:
+                return MyDependency()
+
+            async def shutdown(self, resource: MyDependency) -> None: ...
+
+        self.assertTrue(issubclass(MyAsyncResource, resources.AsyncResource))