AttributeError: 'types.UnionType' object has no attribute '__origin__'

[Manuel Holtgrewe]

Apparently, there is a problem with using union types with drf-pydantic.

The following model ...

class DragenStyleMetric(drf_pydantic.BaseModel):
    """Pydantic model for Dragen-style quality control metric entries"""

    #: The section of the value
    section: str | None
    #: The "entry" in the section can be empty or the read group / sample
    entry: str | None
    #: The name of the metric
    name: str | None
    #: The count / ratio / time / etc. value
    value: int | float | str | None
    #: The count as percentage / seconds
    value_float: float | None = None

... leads to the following error:

  File "/home/holtgrem_c/.local/share/virtualenvs/varfish-server-7_Oac6I8/lib/python3.10/site-packages/django/utils/autoreload.py", line 64, in wrapper
    fn(*args, **kwargs)
  File "/home/holtgrem_c/.local/share/virtualenvs/varfish-server-7_Oac6I8/lib/python3.10/site-packages/django/core/management/commands/runserver.py", line 110, in inner_run
    autoreload.raise_last_exception()
  File "/home/holtgrem_c/.local/share/virtualenvs/varfish-server-7_Oac6I8/lib/python3.10/site-packages/django/utils/autoreload.py", line 87, in raise_last_exception
    raise _exception[1]
  File "/home/holtgrem_c/.local/share/virtualenvs/varfish-server-7_Oac6I8/lib/python3.10/site-packages/django/core/management/__init__.py", line 375, in execute
    autoreload.check_errors(django.setup)()
  File "/home/holtgrem_c/.local/share/virtualenvs/varfish-server-7_Oac6I8/lib/python3.10/site-packages/django/utils/autoreload.py", line 64, in wrapper
    fn(*args, **kwargs)
  File "/home/holtgrem_c/.local/share/virtualenvs/varfish-server-7_Oac6I8/lib/python3.10/site-packages/django/__init__.py", line 24, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "/home/holtgrem_c/.local/share/virtualenvs/varfish-server-7_Oac6I8/lib/python3.10/site-packages/django/apps/registry.py", line 114, in populate
    app_config.import_models()
  File "/home/holtgrem_c/.local/share/virtualenvs/varfish-server-7_Oac6I8/lib/python3.10/site-packages/django/apps/config.py", line 301, in import_models
    self.models_module = import_module(models_module_name)
  File "/usr/lib/python3.10/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1050, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1027, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1006, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 688, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 883, in exec_module
  File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed
  File "/home/holtgrem_c/Development/varfish-server/cases_import/models.py", line 32, in <module>
    from cases_qc.io import cramino as io_cramino
  File "/home/holtgrem_c/Development/varfish-server/cases_qc/io/cramino.py", line 7, in <module>
    from cases_qc import models
  File "/home/holtgrem_c/Development/varfish-server/cases_qc/models.py", line 16, in <module>
    class DragenStyleMetric(drf_pydantic.BaseModel):
  File "/home/holtgrem_c/.local/share/virtualenvs/varfish-server-7_Oac6I8/lib/python3.10/site-packages/drf_pydantic/base_model.py", line 13, in __new__
    setattr(cls, "drf_serializer", create_serializer_from_model(cls))
  File "/home/holtgrem_c/.local/share/virtualenvs/varfish-server-7_Oac6I8/lib/python3.10/site-packages/drf_pydantic/parse.py", line 68, in create_serializer_from_model
    fields[field_name] = _convert_field(field)
  File "/home/holtgrem_c/.local/share/virtualenvs/varfish-server-7_Oac6I8/lib/python3.10/site-packages/drf_pydantic/parse.py", line 141, in _convert_field
    if field.type_.__origin__ is typing.Literal:
AttributeError: 'types.UnionType' object has no attribute '__origin__'

[George Bocharov]

Closing this issue because, sadly, DRF doesn't support union types and the intention of this package is to create a faithful mapping to standard DRF. Custom union types would create introspection issues. New v2 release addresses this by throwing an explicit exception when user provides unsupported union type - only optional union like <type> | None is supported.