Fix annotated (#419)

* Fix annotated

* Fix for 3.8

Author: Tinche

HISTORY.md

@@ -34,6 +34,8 @@
   ([#408](https://github.com/python-attrs/cattrs/pull/408))
 - Fix structuring `Final` lists.
   ([#412](https://github.com/python-attrs/cattrs/issues/412))
+- Fix certain cases of structuring `Annotated` types.
+  ([#418](https://github.com/python-attrs/cattrs/issues/418))
 
 
 ## 23.1.2 (2023-06-02)

src/cattrs/converters.py

@@ -917,9 +917,11 @@ def gen_unstructure_annotated(self, type):
         origin = type.__origin__
         return self._unstructure_func.dispatch(origin)
 
-    def gen_structure_annotated(self, type):
+    def gen_structure_annotated(self, type) -> Callable:
+        """A hook factory for annotated types."""
         origin = type.__origin__
-        return self._structure_func.dispatch(origin)
+        hook = self._structure_func.dispatch(origin)
+        return lambda v, _: hook(v, origin)
 
     def gen_unstructure_typeddict(self, cl: Any) -> Callable[[Dict], Dict]:
         """Generate a TypedDict unstructure function.

tests/test_converter.py

@@ -671,21 +671,22 @@ class Inner:
     class Outer:
         i: Annotated[Inner, "test"]
         j: List[Annotated[Inner, "test"]]
+        k: Annotated[Union[Inner, None], "test"]
 
-    orig = Outer(Inner(1), [Inner(1)])
+    orig = Outer(Inner(1), [Inner(1)], Inner(1))
     raw = converter.unstructure(orig)
 
-    assert raw == {"i": {"a": 1}, "j": [{"a": 1}]}
+    assert raw == {"i": {"a": 1}, "j": [{"a": 1}], "k": {"a": 1}}
 
     structured = converter.structure(raw, Outer)
     assert structured == orig
 
     # Now register a hook and rerun the test.
-    converter.register_unstructure_hook(Inner, lambda v: {"a": 2})
+    converter.register_unstructure_hook(Inner, lambda _: {"a": 2})
 
-    raw = converter.unstructure(Outer(Inner(1), [Inner(1)]))
+    raw = converter.unstructure(Outer(Inner(1), [Inner(1)], Inner(1)))
 
-    assert raw == {"i": {"a": 2}, "j": [{"a": 2}]}
+    assert raw == {"i": {"a": 2}, "j": [{"a": 2}], "k": {"a": 2}}
 
     structured = converter.structure(raw, Outer)
-    assert structured == Outer(Inner(2), [Inner(2)])
+    assert structured == Outer(Inner(2), [Inner(2)], Inner(2))