from django.core.exceptions import ValidationError from django.utils.functional import SimpleLazyObject from django.utils.text import format_lazy def prefix_validation_error(error, prefix, code, params): """ Prefix a validation error message while maintaining the existing validation data structure. """ if error.error_list == [error]: error_params = error.params or {} return ValidationError( # We can't simply concatenate messages since they might require # their associated parameters to be expressed correctly which # is not something `format_lazy` does. For example, proxied # ngettext calls require a count parameter and are converted # to an empty string if they are missing it. message=format_lazy( "{} {}", SimpleLazyObject(lambda: prefix % params), SimpleLazyObject(lambda: error.message % error_params), ), code=code, params={**error_params, **params}, ) return ValidationError( [prefix_validation_error(e, prefix, code, params) for e in error.error_list] )