Add ignore_case argument to enum parser

Author: tomgrin10

README.md

@@ -103,7 +103,7 @@ The following are all type-casting methods of `Env`:
 - `env.uuid`
 - `env.log_level`
 - `env.path` (casts to a [`pathlib.Path`](https://docs.python.org/3/library/pathlib.html))
-- `env.enum` (casts to any given enum type in `type` keyword argument)
+- `env.enum` (casts to any given enum type specified in `type` keyword argument, accepts optional `ignore_case` keyword argument)
 
 ## Reading `.env` files
 

environs/__init__.py

@@ -180,11 +180,20 @@ def _preprocess_json(value: str, **kwargs):
 _EnumT = typing.TypeVar("_EnumT", bound=Enum)
 
 
-def _enum_parser(value, *, type: typing.Type[_EnumT], **kwargs) -> _EnumT:
-    try:
-        return type[value]
-    except KeyError:
-        raise ma.ValidationError(f"Not a valid '{type.__name__}' enum.")
+def _enum_parser(value, *, type: typing.Type[_EnumT], ignore_case: bool = False, **kwargs) -> _EnumT:
+    invalid_exc = ma.ValidationError(f"Not a valid '{type.__name__}' enum.")
+
+    if not ignore_case:
+        try:
+            return type[value]
+        except KeyError:
+            raise invalid_exc
+
+    for enum_value in type:
+        if enum_value.name.lower() == value.lower():
+            return enum_value
+
+    raise invalid_exc
 
 
 def _dj_db_url_parser(value: str, **kwargs) -> dict:

tests/test_environs.py

@@ -211,6 +211,20 @@ def test_enum_cast(self, set_env, env):
         set_env({"DAY": "SUNDAY"})
         assert env.enum("DAY", type=DayEnum) == DayEnum.SUNDAY
 
+    def test_enum_cast_ignore_case(self, set_env, env):
+        set_env({"DAY": "suNDay"})
+        assert env.enum("DAY", type=DayEnum, ignore_case=True) == DayEnum.SUNDAY
+
+    def test_invalid_enum(self, set_env, env):
+        set_env({"DAY": "suNDay"})
+        with pytest.raises(environs.EnvError):
+            assert env.enum("DAY", type=DayEnum)
+
+    def test_invalid_enum_ignore_case(self, set_env, env):
+        set_env({"DAY": "SonDAY"})
+        with pytest.raises(environs.EnvError):
+            assert env.enum("DAY", type=DayEnum, ignore_case=True)
+
 
 class TestEnvFileReading:
     def test_read_env(self, env):