SQL Alchemy enum validation conflict with validate function - python-3.x

Question

I am trying to use the sqlalchemy enum type without creating a native DB ENUM column but still having sqlalchemy validates enum inputs.
So I have this declaration :
from sqlalchemy import Column
from sqlalchemy import Integer
from sqlalchemy import Enum as SaEnum
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import validates
import enum
Base = declarative_base()
class DummyEnum(enum.Enum):
NAME_1 = "NAME_1"
NAME_2 = "NAME_2"
class SAEnumVarcharTable(Base):
__tablename__ = "test_table"
id = Column(Integer, primary_key=True)
uut_column = Column(SaEnum(DummyEnum, native_enum=False, validate_strings=True), default=DummyEnum.NAME_1)
#validates('uut_column')
def validate_uut_column(self, key, uut_value):
return uut_value.upper()
I want the validation returning the string in upper case and only then do the Enum validation...
Is it possible?
because when I do :
connection.execute(insert(SAEnumVarcharTable), {"uut_column" : "name_1"})
it does raise a LookupError where I would expect to be accepted as valid input (first goes to the validates functions -> return an uppercase string -> do the Enum validation)...Is it somehow possible?

Answer 1

Validators are only called when modifying an instance's attributes, e.g.:
instance = SAEnumVarcharTable()
instance.uut_column = "name_1"
In your case, you would need to override sqlalchemy.Enum's _db_value_for_elem:
class UpperCaseEnum(SaEnum):
def _db_value_for_elem(self, elem):
return super()._db_value_for_elem(elem.upper())
# uut_column = Column(SaEnum(...), ...)
uut_column = Column(UpperCaseEnum(...), ...)
Aside
Validator implementation
validate_uut_column is not implemented correctly.
instance = SAEnumVarcharTable()
instance.uut_column = "name_0" # No error, expected LookupError
instance.uut_column = "name_1" # Ok
print(instance.uut_column == DummyEnum.NAME_1) # False, expected True
print(instance.uut_column.value == "NAME_1") # AttributeError: 'str' object has no attribute 'value'
instance.uut_column = DummyEnum.NAME_1 # AttributeError: 'DummyEnum' object has no attribute 'upper'
Instead, it should be:
#validates('uut_column')
def validate_uut_column(self, key, uut_value):
# return uut_value.upper()
return uut_value if uut_value in DummyEnum else DummyEnum[uut_value.upper()]
instance = SAEnumVarcharTable()
instance.uut_column = "name_0" # LookupError, as expected
instance.uut_column = "name_1" # Ok
print(instance.uut_column == DummyEnum.NAME_1) # True, as expected
print(instance.uut_column.value == "NAME_1") # True, as expected
instance.validate_uut_column = DummyEnum.NAME_1 # Ok