Fix unknown enum to dict

betterproto2/src/betterproto2/__init__.py

@@ -588,6 +588,11 @@ def _value_to_dict(
         return b64encode(value).decode("utf8"), not bool(value)
     if proto_type == TYPE_ENUM:
         enum_value = field_type(value)
+
+        # If we don't know the definition of this variant, we fall back to the value.
+        if not enum_value.name:
+            return enum_value.value, not bool(value)
+
         return enum_value.proto_name or enum_value.name, not bool(value)
     if proto_type in (TYPE_FLOAT, TYPE_DOUBLE):
         return _dump_float(value), not bool(value)

betterproto2/tests/test_all_definition.py

@@ -17,4 +17,15 @@ def test_all_definition():
         "TestSyncStub",
         "ThingType",
     )
-    assert enum.__all__ == ("ArithmeticOperator", "Choice", "EnumMessage", "HttpCode", "NoStriping", "Test")
+    assert enum.__all__ == (
+        "ArithmeticOperator",
+        "Choice",
+        "EnumMessage",
+        "HttpCode",
+        "NewVersion",
+        "NewVersionMessage",
+        "NoStriping",
+        "OldVersion",
+        "OldVersionMessage",
+        "Test",
+    )

betterproto2/tests/test_enum.py

@@ -98,3 +98,13 @@ def test_enum_to_dict() -> None:
         "arithmeticOperator": "ARITHMETIC_OPERATOR_PLUS",  # The original proto name must be preserved
         "noStriping": "NO_STRIPING_A",
     }
+
+
+def test_unknown_variant_to_dict() -> None:
+    from tests.outputs.enum.enum import NewVersion, NewVersionMessage, OldVersionMessage
+
+    serialized = bytes(NewVersionMessage(new_version=NewVersion.V3))
+
+    deserialized = OldVersionMessage.parse(serialized)
+
+    assert deserialized.to_dict() == {"oldVersion": 3}

betterproto2_compiler/tests/inputs/enum/enum.proto

@@ -43,3 +43,24 @@ message EnumMessage {
     ArithmeticOperator arithmetic_operator = 1;
     NoStriping no_striping = 2;
 }
+
+enum OldVersion {
+    OLD_VERSION_UNSPECIFIED = 0;
+    OLD_VERSION_V1 = 1;
+    OLD_VERSION_V2 = 2;
+}
+
+message OldVersionMessage {
+    OldVersion old_version = 1;
+}
+
+enum NewVersion {
+    NEW_VERSION_UNSPECIFIED = 0;
+    NEW_VERSION_V1 = 1;
+    NEW_VERSION_V2 = 2;
+    NEW_VERSION_V3 = 3;
+}
+
+message NewVersionMessage {
+    NewVersion new_version = 1;
+}