Test passing internal types as default

CHANGELOG.md

@@ -2,6 +2,12 @@
 
 ## 12.0.0 (unreleased)
 
+Features:
+
+- `Env.enum` allows passing an `Enum` as `default`.
+
+Other changes:
+
 - Support marshmallow 4.
 - Support Python 3.9-3.13.
 - _Backwards-incompatible_: Make `Field` classes private. Users should

src/environs/__init__.py

@@ -296,6 +296,9 @@ def _preprocess_json(value: str | typing.Mapping | list, **kwargs):
 
 
 def _enum_parser(value, type: type[_EnumT], ignore_case: bool = False) -> _EnumT:
+    if isinstance(value, type):
+        return value
+
     invalid_exc = ma.ValidationError(f"Not a valid '{type.__name__}' enum.")
 
     if not ignore_case:

tests/test_environs.py

@@ -231,6 +231,24 @@ def test_date_cast(self, set_env, env):
         set_env({"DATE": date.isoformat()})
         assert env.date("DATE") == date
 
+    @pytest.mark.xfail(
+        MARSHMALLOW_VERSION.major < 4,
+        reason="marshmallow 3 does not allow all fields to accept internal types",
+    )
+    @pytest.mark.parametrize(
+        ("method_name", "value"),
+        [
+            pytest.param("timedelta", dt.timedelta(seconds=42), id="timedelta"),
+            pytest.param("date", dt.date(2020, 1, 1), id="date"),
+            pytest.param("datetime", dt.datetime(2020, 1, 1, 1, 2, 3), id="datetime"),
+            pytest.param("time", dt.time(1, 2, 3), id="time"),
+            pytest.param("uuid", uuid.uuid4(), id="uuid"),
+        ],
+    )
+    def test_default_can_be_set_to_internal_type(self, env, method_name: str, value):
+        method = getattr(env, method_name)
+        assert method("NOTFOUND", value) == value
+
     def test_timedelta_cast(self, set_env, env):
         # default values
         assert env.timedelta("TIMEDELTA", "42") == dt.timedelta(seconds=42)
@@ -364,6 +382,11 @@ def test_invalid_enum_ignore_case(self, set_env, env):
         with pytest.raises(environs.EnvError):
             assert env.enum("DAY", type=DayEnum, ignore_case=True)
 
+    def test_enum_default(self, env: environs.Env):
+        assert (
+            env.enum("NOTFOUND", type=DayEnum, default=DayEnum.SUNDAY) == DayEnum.SUNDAY
+        )
+
 
 class TestEnvFileReading:
     def test_read_env(self, env):