Asset Validator (Python)

The following is a functional skeletal example of an Editor Asset Validator class in Python.

Notice how the class uses @unreal.uclass() and @unreal.ufunction() decorators to be treated as a valid UClass (see UClass Decorators)

import unreal

# Sample implementation of an Editor Asset Validator in Python
@unreal.uclass()
class EditorValidatorConcrete(unreal.EditorValidatorBase):
    def __init__(self, *arg, **kwds):
        super(EditorValidatorConcrete, self).__init__(*arg, **kwds)

    # Tests an asset for validity and either 
    # passes (by calling self.asset_passes and returning VALID)
    # or fails (by calling self.asset_fails and returning INVALID)
    #
    # WATCH OUT!: This ufunction has two return values, because the parameter 
    # validation_errors is marked as pass-by-reference in the parent - UPARAM(ref)
    @unreal.ufunction(override=True)
    def validate_loaded_asset(self, asset, validation_errors):
        self.asset_fails(asset, "asset failed", validation_errors)
        return (unreal.DataValidationResult.INVALID, validation_errors)

    # Tests an asset's type or properties to discern
    # whether it should be validated by this class
    @unreal.ufunction(override=True)
    def can_validate_asset(self, asset):
        return True

# Unlike EditorValidatorBase subclasses in C++, which are registered automatically,
# EditorValidatorBase subclasses in Python must be registered manually:
if __name__ == "__main__":
    editor_validator_subsystem = unreal.get_editor_subsystem(unreal.EditorValidatorSubsystem)
    validator = EditorValidatorConcrete()
    editor_validator_subsystem.add_validator(validator)

For more information on Asset Validators, see the following pages of the Unreal Engine Documentation:

• Data Validation

• UEditorValidatorBase (C++)

• unreal.EditorValidatorBase (Python)