feat: Try to inject parameter value if default value is None

src/in_n_out/_store.py

@@ -778,7 +778,10 @@ def _exec(*args: P.args, **kwargs: P.kwargs) -> R:
                 # first, get and call the provider functions for each parameter type:
                 _injected_names: set[str] = set()
                 for param in sig.parameters.values():
-                    if param.name not in bound.arguments:
+                    if (
+                        param.name not in bound.arguments
+                        or bound.arguments[param.name] is None
+                    ):
                         provided = self.provide(param.annotation)
                         if provided is not None or is_optional(param.annotation):
                             logger.debug(

tests/test_injection.py

@@ -296,3 +296,18 @@ def f(i: Optional[Thing]) -> Optional[Thing]:
     thing = Thing()
     with register(providers={Optional[Thing]: lambda: thing}):
         assert inject(f)() is thing
+
+
+def test_inject_into_optional_with_default() -> None:
+    class Thing: ...
+
+    def f(i: Optional[Thing] = None) -> Optional[Thing]:
+        return i
+
+    thing = Thing()
+    with register(providers={Optional[Thing]: lambda: thing}):
+        assert inject(f)() is thing
+    with register(providers={Thing: lambda: thing}):
+        assert inject(f)() is thing
+
+    assert inject(f)() is None