Union types that contain a type that require an avrocschema.types specifier fail to generate schema

Describe the bug A field with a Union type, where the Union contains a type that requires a dataclasses_avroschema.types default to provide additional metadata (Decimal, Enum, etc) fails to generate a schema.

To Reproduce

@dataclass
class TestEnum(AvroModel):
    OptionalEnum: typing.Optional[types.Enum] = types.Enum(['Mr', 'Mrs', 'Miss', 'Ms'])
    # DateEnum = typing.Union[datetime, types.Enum] = types.Enum(['Mr', 'Mrs', 'Miss', 'Ms'])
    # DecimalEnum = typing.Union[decimal.Decimal, types.Enum] = (types.Decimal(precision=2, scale=1), types.Enum(['Mr', 'Mrs', 'Miss', 'Ms']))

print(TestEnum.avro_schema())

Generates the following stacktrace

faust_1  | Traceback (most recent call last):
faust_1  |   File "/usr/local/lib/python3.8/runpy.py", line 194, in _run_module_as_main
faust_1  |     return _run_code(code, main_globals, None,
faust_1  |   File "/usr/local/lib/python3.8/runpy.py", line 87, in _run_code
faust_1  |     exec(code, run_globals)
faust_1  |   File "/app/proj/__main__.py", line 17, in <module>
faust_1  |     print(TestEnum.avro_schema())
faust_1  |   File "/usr/local/lib/python3.8/site-packages/dataclasses_avroschema/schema_generator.py", line 58, in avro_schema
faust_1  |     return json.dumps(cls.generate_schema(schema_type=AVRO).render())
faust_1  |   File "/usr/local/lib/python3.8/site-packages/dataclasses_avroschema/schema_generator.py", line 46, in generate_schema
faust_1  |     cls.schema_def = cls._generate_avro_schema()
faust_1  |   File "/usr/local/lib/python3.8/site-packages/dataclasses_avroschema/schema_generator.py", line 54, in _generate_avro_schema
faust_1  |     return schema_definition.AvroSchemaDefinition("record", cls.klass, metadata=cls.metadata)
faust_1  |   File "<string>", line 9, in __init__
faust_1  |   File "/usr/local/lib/python3.8/site-packages/dataclasses_avroschema/schema_definition.py", line 55, in __post_init__
faust_1  |     self.fields = self.parse_dataclasses_fields()
faust_1  |   File "/usr/local/lib/python3.8/site-packages/dataclasses_avroschema/schema_definition.py", line 60, in parse_dataclasses_fields
faust_1  |     return self.parse_fields()
faust_1  |   File "/usr/local/lib/python3.8/site-packages/dataclasses_avroschema/schema_definition.py", line 63, in parse_fields
faust_1  |     return [
faust_1  |   File "/usr/local/lib/python3.8/site-packages/dataclasses_avroschema/schema_definition.py", line 64, in <listcomp>
faust_1  |     AvroField(
faust_1  |   File "/usr/local/lib/python3.8/site-packages/dataclasses_avroschema/fields.py", line 820, in field_factory
faust_1  |     return container_klass(  # type: ignore
faust_1  |   File "<string>", line 10, in __init__
faust_1  |   File "/usr/local/lib/python3.8/site-packages/dataclasses_avroschema/fields.py", line 355, in __post_init__
faust_1  |     self.unions = self.generate_unions_type()
faust_1  |   File "/usr/local/lib/python3.8/site-packages/dataclasses_avroschema/fields.py", line 382, in generate_unions_type
faust_1  |     unions.append(default_field.get_avro_type())
faust_1  |   File "/usr/local/lib/python3.8/site-packages/dataclasses_avroschema/fields.py", line 449, in get_avro_type
faust_1  |     "symbols": self.default.symbols,
faust_1  | AttributeError: '_MISSING_TYPE' object has no attribute 'symbols'

Expected behavior An AvroSchema something like:

 {"type": "record", "name": "TestEnum", "fields": [{"name": "OptionalEnum", "type": ["null", {"type": "enum", "name": "OptionalEnum", "symbols": ["Mr", "Mrs", "Miss", "Ms"]}]}], "doc": "TestEnum(OptionalEnum: dataclasses_avroschema.types.Enum = ['Mr', 'Mrs', 'Miss', 'Ms'])"}

[aaronkub]

On second thought, I will commit to getting a PR open this weekend. 🙂

[marcosschroh]

closed by https://github.com/marcosschroh/dataclasses-avroschema/pull/153