fixed serialization bug

monty/json.py

@@ -412,17 +412,21 @@ def default(self, o) -> dict:  # pylint: disable=E0202
         try:
             if pydantic is not None and isinstance(o, pydantic.BaseModel):
                 d = o.dict()
-            elif isinstance(o, Enum):
-                d = {"value": o.value}
             elif (
                 dataclasses is not None
                 and (not issubclass(o.__class__, MSONable))
                 and dataclasses.is_dataclass(o)
             ):
                 # This handles dataclasses that are not subclasses of MSONAble.
                 d = dataclasses.asdict(o)
-            else:
+            elif hasattr(o, "as_dict"):
                 d = o.as_dict()
+            elif isinstance(o, Enum):
+                d = {"value": o.value}
+            else:
+                raise TypeError(
+                    f"Object of type {o.__class__.__name__} is not JSON serializable"
+                )
 
             if "@module" not in d:
                 d["@module"] = str(o.__class__.__module__)

tests/test_json.py

@@ -20,11 +20,6 @@
 test_dir = os.path.join(os.path.dirname(os.path.abspath(__file__)), "test_files")
 
 
-class A(Enum):
-    name_a = "value_a"
-    name_b = "value_b"
-
-
 class GoodMSONClass(MSONable):
     def __init__(self, a, b, c, d=1, *values, **kwargs):
         self.a = a
@@ -105,6 +100,23 @@ def my_callable(a, b):
     return a + b
 
 
+class EnumNoAsDict(Enum):
+    name_a = "value_a"
+    name_b = "value_b"
+
+
+class EnumAsDict(Enum):
+    name_a = "value_a"
+    name_b = "value_b"
+
+    def as_dict(self):
+        return {"v": self.value}
+
+    @classmethod
+    def from_dict(cls, d):
+        return cls(d["v"])
+
+
 class EnumTest(MSONable, Enum):
     a = 1
     b = 2
@@ -815,7 +827,13 @@ def test_dataclass(self):
         assert isinstance(ndc2, NestedDataClass)
 
     def test_enum(self):
-        s = MontyEncoder().encode(A.name_a)
+        s = MontyEncoder().encode(EnumNoAsDict.name_a)
         p = MontyDecoder().decode(s)
         assert p.name == "name_a"
         assert p.value == "value_a"
+
+        na1 = EnumAsDict.name_a
+        d_ = na1.as_dict()
+        assert d_ == {"v": "value_a"}
+        na2 = EnumAsDict.from_dict(d_)
+        assert na2 == na1