Add support for Annotated types (#219)

This is a relatively simple and straightforward implementation with minimal changes and seems to work fine.

Resolves #217

injector/__init__.py

@@ -705,6 +705,8 @@ def _punch_through_alias(type_: Any) -> type:
         and type(type_).__name__ == 'NewType'
     ):
         return type_.__supertype__
+    elif isinstance(type_, _AnnotatedAlias) and getattr(type_, '__metadata__', None) is not None:
+        return type_.__origin__
     else:
         return type_
 

injector_test.py

@@ -18,6 +18,11 @@
 import traceback
 import warnings
 
+if sys.version_info >= (3, 9):
+    from typing import Annotated
+else:
+    from typing_extensions import Annotated
+
 from typing import Dict, List, NewType
 
 import pytest
@@ -1682,3 +1687,70 @@ def function1(a: int | str) -> None:
         pass
 
     assert get_bindings(function1) == {'a': Union[int, str]}
+
+
+# test for https://github.com/python-injector/injector/issues/217
+def test_annotated_instance_integration_works():
+    UserID = Annotated[int, "user_id"]
+
+    def configure(binder):
+        binder.bind(UserID, to=123)
+
+    injector = Injector([configure])
+    assert injector.get(UserID) == 123
+
+
+def test_annotated_class_integration_works():
+    class Shape(abc.ABC):
+        pass
+
+    class Circle(Shape):
+        pass
+
+    first = Annotated[Shape, "first"]
+
+    def configure(binder):
+        binder.bind(first, to=Circle)
+
+    injector = Injector([configure])
+    assert isinstance(injector.get(first), Circle)
+
+
+def test_annotated_meta_separate_bindings():
+    first = Annotated[int, "first"]
+    second = Annotated[int, "second"]
+
+    def configure(binder):
+        binder.bind(first, to=123)
+        binder.bind(second, to=456)
+
+    injector = Injector([configure])
+    assert injector.get(first) == 123
+    assert injector.get(second) == 456
+    assert injector.get(first) != injector.get(second)
+
+
+def test_annotated_origin_separate_bindings():
+    UserID = Annotated[int, "user_id"]
+
+    def configure(binder):
+        binder.bind(UserID, to=123)
+        binder.bind(int, to=456)
+
+    injector = Injector([configure])
+    assert injector.get(UserID) == 123
+    assert injector.get(int) == 456
+    assert injector.get(UserID) != injector.get(int)
+
+
+def test_annotated_non_comparable_types():
+    foo = Annotated[int, float("nan")]
+    bar = Annotated[int, object()]
+
+    def configure(binder):
+        binder.bind(foo, to=123)
+        binder.bind(bar, to=456)
+
+    injector = Injector([configure])
+    assert injector.get(foo) == 123
+    assert injector.get(bar) == 456