DelimitedDigitsPostalCode does not implement if_missing

[danclark5]

For some reason DelimitedDigitsPostalCode doesn't implement if_missing. I am wondering if this was done on purpose.

A quick traversal through the classes

• DelimitedDigitsPostalCode subclasses validators.Regex
• Regex subclasses api.FancyValidator
• FancyValidator subclasses api.Validator

FancyValidator sets if_missing to NoDefault, but Regex and DelimitedDigitPostalCode do not override it with anything.

A workaround is to just manually set postal_code_schema_validation_field.if_missing = None in the schema

Thanks to Vsevolod Kulaga for pointing all of this out in https://stackoverflow.com/questions/44387896/formencode-is-ignoring-if-missing/44397189#44397189

[precious]

I just have did double check and found that in formencode 1.3.1 validator DelimitedDigitsPostalCode handles if_missing correctly:

from formencode import national, Schema, validators

class TestValidator(Schema):
    allow_extra_fields = True
    filter_extra_fields = True
    postal_code_5_digits = national.DelimitedDigitsPostalCode(5, None, not_empty=False, if_missing='')

print(TestValidator.to_python({}))
# {'postal_code_5_digits': ''} is printed

But USPostalCode validator ignores if_missing though it's implemented as combination of two DelimitedDigitsPostalCode validators:

# from file formencode/national.py
def USPostalCode(*args, **kw):
    """
    US Postal codes (aka Zip Codes).

    ::

        >>> uspc = USPostalCode()
        >>> uspc.to_python('55555')
        '55555'
        >>> uspc.to_python('55555-5555')
        '55555-5555'
        >>> uspc.to_python('5555')
        Traceback (most recent call last):
            ...
        Invalid: Please enter a zip code (5 digits)
    """
    return Any(DelimitedDigitsPostalCode(5, None, *args, **kw),
               DelimitedDigitsPostalCode([5, 4], '-', *args, **kw))

So the root issue is in validator class Any that inherits class CompoundValidator (file formencode/compound.py). There are two validators in file formencode/compound.py that inherit CompoundValidator: Any and All. Validator class All implements its own property if_missing:

# from file formencode/compound.py
class All(CompoundValidator):

    # <...>

    @property
    def if_missing(self):
        for validator in self.validators:
            v = validator.if_missing
            if v is not NoDefault:
                return v
        return NoDefault

Meanwhile validator class Any does not have such property. That's why USPostalCode ignores if_missing -- it's just an instance of Any.

---

Looks like both compound validators -- All and Any should be reviewed, and all options -- if_missing, not_empty, if_empty, etc should be checked for them.

[danclark5]

Thanks for pointing that out. I should have taken the time to research before opening the issue, my mistake.