# -*- coding: utf-8 -*-
"""
Script that demonstrates DataClass Bug with Typo-Unsafe Attributes
Also provides a solution in the form of a SafeDataClass with adjusted __setattr__
"""
import dataclasses

# a standard DataClass:
@dataclass
class DataRecordClass:
    attribute_1: float = 3.0
    
# an extended DataClass, which is typo-safe:
@dataclass
class SafeDataRecordClass:
    """Instances of this class will raise an Error if users try to set an undeclared attribute."""
    attribute_1: float = 3.0

    def __setattr__(self, name, value):
        # raise Error if field is not declared in the dataclass
        for field in dataclasses.fields(self):
            if field.name == name:
                super().__setattr__(name, value)
                return
        # raise error when field is not found:
        raise AttributeError(type(self).__name__ + ' attribute \'' + name + '\' does not exist')


##########
## Main ##
##########

print('')
print('-- Unsafe Data Record: -- ')
print('')

unsafe_record = DataRecordClass()
print('print unsafe_record:', unsafe_record)

# add a field to 'unsafe_record'
# I would expect an Error...
unsafe_record.new_attribute = 5.0  

print('print unsafe_record.new_attribute:', unsafe_record.new_attribute)
print('print unsafe_record:', unsafe_record)


print('')
print('-- Safe Data Record: --')
print('')

safe_record = SafeDataRecordClass()
# for 'safe_record' setting an unexistent attribute does raise an Error, as expected:
print('set safe record new_attribute:')
safe_record.new_attribute = 5.0