patch_data should have same truthy test as validators.Optional()?

[larkin]

If you're using forms for handling patch requests, you have to use validators.Optional() at the end of your validation chain for all fields.

That said, the test that validators.Optional() uses to determine if a field is blank is different than the test that patch_data uses. Entering white space for a field will match validators.Optional(), so validations will be skipped, but the resulting patch_dict will contain the field still.

For example:

from wtforms import Form, fields, validators

import wtforms_json

wtforms_json.init()

class PatchUserForm(Form):
    email = fields.TextField(
        'email',
        [validators.Email('Invalid email address.'), validators.Optional()]
    )

form = PatchUserForm.from_json({'email': ' '})
assert form.validate()
assert 'email' not in form.patch_data # will fail here.

The argument against this is that people should be able to set fields to null or blank via patch, but in that case wtforms-json could check the field's optional flag, yea?

For my use case, I'm using a custom validator in place of validators.Optional that doesn't consider ' ' falsy.

[alanhamlett]

This is related to Issue #20.

Possible fix would be to monkey-patch validators.Optional to NOT stop validating when the field is blank. That way you could use validators.Optional with validators.DataRequired. When the field is blank, the DataRequired validator raises an error if it was used. When the field is missing, the Optional validator stops validating like normal and patch_data will NOT include that field.