feat: add __doc__ attribute to _MISSING_TYPE and test for None value

Author: tlambert03

src/fieldz/_types.py

@@ -31,9 +31,10 @@
 
 class _MISSING_TYPE(enum.Enum):
     MISSING = "MISSING"
+    __doc__ = None
 
     def __repr__(self) -> str:
-        return self.value
+        return str(self.value)
 
 
 @dataclasses.dataclass(**DC_KWARGS)

tests/test_fieldz.py

@@ -256,3 +256,9 @@ class Model(TypedDict):
         Field(name="d", type=bool),
         Field(name="e", type=list[int]),
     )
+
+
+def test_missing_has_no_doc() -> None:
+    """MISSING.__doc__ should be None, not inherited enum doc. gh-41."""
+    assert Field.MISSING.__doc__ is None
+    assert getattr(Field.MISSING, "__doc__", None) is None