Fix preconf string Enum keys

HISTORY.rst

@@ -5,6 +5,7 @@ History
 -------------------
 * Add PEP 563 (string annotations) for dataclasses.
   (`#195 <https://github.com/python-attrs/cattrs/issues/195>`_)
+* Fix handling of dictionaries with string Enum keys for bson, orjson, and tomlkit.
 
 1.9.0 (2021-12-06)
 ------------------

src/cattr/preconf/bson.py

@@ -12,12 +12,17 @@ def configure_converter(converter: GenConverter):
     Configure the converter for use with the bson library.
 
     * sets are serialized as lists
-    * mapping keys are coerced into strings when unstructuring
+    * non-string mapping keys are coerced into strings when unstructuring
     """
 
     def gen_unstructure_mapping(cl: Any, unstructure_to=None):
+        key_handler = str
+        if (args := getattr(cl, "__args__", None)) and issubclass(
+            args[0], str
+        ):
+            key_handler = None
         return converter.gen_unstructure_mapping(
-            cl, unstructure_to=unstructure_to, key_handler=str
+            cl, unstructure_to=unstructure_to, key_handler=key_handler
         )
 
     converter._unstructure_func.register_func_list(

src/cattr/preconf/orjson.py

@@ -1,6 +1,7 @@
 """Preconfigured converters for orjson."""
 from base64 import b85decode, b85encode
 from datetime import datetime
+from enum import Enum
 from typing import Any
 
 from .._compat import Set, is_mapping
@@ -14,6 +15,7 @@ def configure_converter(converter: GenConverter):
     * bytes are serialized as base85 strings
     * datetimes are serialized as ISO 8601
     * sets are serialized as lists
+    * string enum mapping keys have special handling
     * mapping keys are coerced into strings when unstructuring
     """
     converter.register_unstructure_hook(
@@ -27,8 +29,18 @@ def configure_converter(converter: GenConverter):
     )
 
     def gen_unstructure_mapping(cl: Any, unstructure_to=None):
+        key_handler = str
+        if (
+            (args := getattr(cl, "__args__", None))
+            and issubclass(args[0], str)
+            and issubclass(args[0], Enum)
+        ):
+
+            def key_handler(v):
+                return v.value
+
         return converter.gen_unstructure_mapping(
-            cl, unstructure_to=unstructure_to, key_handler=str
+            cl, unstructure_to=unstructure_to, key_handler=key_handler
         )
 
     converter._unstructure_func.register_func_list(

src/cattr/preconf/tomlkit.py

@@ -23,8 +23,13 @@ def configure_converter(converter: GenConverter):
     )
 
     def gen_unstructure_mapping(cl: Any, unstructure_to=None):
+        key_handler = str
+        if (args := getattr(cl, "__args__", None)) and issubclass(
+            args[0], str
+        ):
+            key_handler = None
         return converter.gen_unstructure_mapping(
-            cl, unstructure_to=unstructure_to, key_handler=str
+            cl, unstructure_to=unstructure_to, key_handler=key_handler
         )
 
     converter._unstructure_func.register_func_list(

tests/test_preconf.py

@@ -71,6 +71,7 @@ class AStringEnum(str, Enum):
     an_int_enum: AnIntEnum
     a_str_enum: AStringEnum
     a_datetime: datetime
+    a_string_enum_dict: Dict[AStringEnum, int]
 
 
 @composite
@@ -161,6 +162,12 @@ def everythings(
         Everything.AnIntEnum.A,
         Everything.AStringEnum.A,
         draw(dts),
+        draw(
+            dictionaries(
+                just(Everything.AStringEnum.A),
+                integers(min_value=min_int, max_value=max_int),
+            )
+        ),
     )
 
 
@@ -204,7 +211,7 @@ def test_orjson(everything: Everything):
     from orjson import loads as orjson_loads
 
     converter = orjson_make_converter()
-    raw = orjson_dumps(converter.unstructure(everything))
+    raw = orjson_dumps(r := converter.unstructure(everything))
     assert converter.structure(orjson_loads(raw), Everything) == everything