Generate rename metadata for aliases in generated hooks

HISTORY.md

@@ -21,6 +21,8 @@ Our backwards-compatibility policy can be found [here](https://github.com/python
   ([#696](https://github.com/python-attrs/cattrs/pull/696))
 - Use the optional `_value_` type hint to structure and unstructure enums if present.
   ([#699](https://github.com/python-attrs/cattrs/issues/699))
+- Aliases (when in use) now properly generate rename metadata in generated hooks.
+  ([#706](https://github.com/python-attrs/cattrs/issues/706) [#710](https://github.com/python-attrs/cattrs/pull/710))
 - _cattrs_ now tracks performance using [codspeed](https://codspeed.io/python-attrs/cattrs).
   ([#703](https://github.com/python-attrs/cattrs/pull/703))
 - The {mod}`tomlkit <cattrs.preconf.tomlkit>` preconf converter now properly handles native `date` objects when structuring.

src/cattrs/gen/__init__.py

@@ -4,7 +4,7 @@
 from collections.abc import Callable, Iterable, Mapping
 from typing import TYPE_CHECKING, Any, Final, Literal, TypeVar
 
-from attrs import NOTHING, Attribute, Converter, Factory
+from attrs import NOTHING, Attribute, Converter, Factory, evolve
 from typing_extensions import NoDefault
 
 from .._compat import (
@@ -124,6 +124,8 @@ def make_dict_unstructure_fn_from_attrs(
             continue
         if override.rename is None:
             kn = attr_name if not _cattrs_use_alias else a.alias
+            if kn != attr_name:
+                kwargs[attr_name] = evolve(override, rename=kn)
         else:
             kn = override.rename
         d = a.default
@@ -435,6 +437,8 @@ def make_dict_structure_fn_from_attrs(
             ian = a.alias
             if override.rename is None:
                 kn = an if not _cattrs_use_alias else a.alias
+                if kn != an:
+                    kwargs[an] = evolve(override, rename=kn)
             else:
                 kn = override.rename
 
@@ -562,6 +566,8 @@ def make_dict_structure_fn_from_attrs(
 
             if override.rename is None:
                 kn = an if not _cattrs_use_alias else a.alias
+                if kn != an:
+                    kwargs[an] = evolve(override, rename=kn)
             else:
                 kn = override.rename
             allowed_fields.add(kn)
@@ -631,6 +637,8 @@ def make_dict_structure_fn_from_attrs(
 
                 if override.rename is None:
                     kn = an if not _cattrs_use_alias else a.alias
+                    if kn != an:
+                        kwargs[an] = evolve(override, rename=kn)
                 else:
                     kn = override.rename
                 allowed_fields.add(kn)

tests/test_gen_dict.py

@@ -419,6 +419,30 @@ class A:
     )
 
 
+def test_alias_implicit_rename(converter: BaseConverter) -> None:
+    """Attributes with aliases generate rename metadata."""
+
+    @define
+    class A:
+        a: int = field(alias="b")
+        c: int = field(alias="d", default=1)
+
+    u_fn = make_dict_unstructure_fn(A, converter, _cattrs_use_alias=True)
+    s_fn = make_dict_structure_fn(A, converter, _cattrs_use_alias=True)
+
+    assert u_fn.overrides["a"].rename == "b"
+    assert s_fn.overrides["a"].rename == "b"
+    assert u_fn.overrides["c"].rename == "d"
+    assert s_fn.overrides["c"].rename == "d"
+
+    converter.register_unstructure_hook(A, u_fn)
+    converter.register_structure_hook(A, s_fn)
+
+    assert converter.unstructure(A(1)) == {"b": 1, "d": 1}
+    assert converter.structure({"b": 1}, A) == A(1)
+    assert converter.structure({"b": 1, "d": 2}, A) == A(1, 2)
+
+
 def test_init_false(converter: BaseConverter) -> None:
     """By default init=False keys are ignored."""