Support PEP 604 optional & union types (#203)

Fixes #202.

injector/__init__.py

@@ -1166,6 +1166,10 @@ def __getattribute__(self, name: str) -> Any:
 
 
 def _infer_injected_bindings(callable: Callable, only_explicit_bindings: bool) -> Dict[str, type]:
+    def _is_new_union_type(instance: Any) -> bool:
+        new_union_type = getattr(types, 'UnionType', None)
+        return new_union_type is not None and isinstance(instance, new_union_type)
+
     spec = inspect.getfullargspec(callable)
 
     try:
@@ -1204,7 +1208,7 @@ def _infer_injected_bindings(callable: Callable, only_explicit_bindings: bool) -
 
         if only_explicit_bindings and _inject_marker not in metadata or _noinject_marker in metadata:
             del bindings[k]
-        elif _is_specialization(v, Union):
+        elif _is_specialization(v, Union) or _is_new_union_type(v):
             # We don't treat Optional parameters in any special way at the moment.
             union_members = v.__args__
             new_members = tuple(set(union_members) - {type(None)})

injector_test.py

@@ -11,7 +11,7 @@
 """Functional tests for the "Injector" dependency injection framework."""
 
 from contextlib import contextmanager
-from typing import Any, NewType, Optional
+from typing import Any, NewType, Optional, Union
 import abc
 import sys
 import threading
@@ -1516,3 +1516,19 @@ def function11(a: int) -> 'InvalidForwardReference':
         pass
 
     assert get_bindings(function11) == {'a': int}
+
+
+# Tests https://github.com/alecthomas/injector/issues/202
+@pytest.mark.skipif(sys.version_info < (3, 10), reason="Requires Python 3.10+")
+def test_get_bindings_for_pep_604():
+    @inject
+    def function1(a: int | None) -> None:
+        pass
+
+    assert get_bindings(function1) == {'a': int}
+
+    @inject
+    def function1(a: int | str) -> None:
+        pass
+
+    assert get_bindings(function1) == {'a': Union[int, str]}