CODEWITHSUNDEEP
djangovalidationutf-8django-validationftfy
d33tah
d33tah

Reputation: 11561

How to plug in a specific validator for all cases of a built-in type?

I recently noticed that some of my entries in a database coming from users contain incorrectly encoded strings, such as ó when ó was clearly meant. It's coming from copy-pasting of other websites that aren't properly encoded, which is beyond my control. I discovered that I can add this validator to catch such cases and raise an exception - here's an example with an attached model:

from django.db import models

from django.utils.translation import gettext_lazy as _
from django.core.exceptions import ValidationError
import ftfy

def validate_ftfy(value):
    value_ftfy = ftfy.ftfy(value)
    if value_ftfy != value:
        raise ValidationError(
            _('Potential UTF-8 encoding error: %(value)r'
              ' decoded to %(value_ftfy)r.'),
            params={'value': value, 'value_ftfy': value_ftfy}
        )

class Message(models.Model):
    content = models.CharField(max_length=1000, validators=[validate_ftfy])

    def save(self, *args, **kwargs):
        self.full_clean()
        return super(Message, self).save(*args, **kwargs)

The problem is that now that I discovered it, I see no point skipping it in any of my instances of CharField, TextField and the like. Is there a way to plug in this validator to all data types, so that if anything non-binary has invalid UTF-8, I can count on it not making it to the database?

Upvotes: 0

Views: 35

Answers (1)

bug
bug

Reputation: 4150

There is no hook to add additional validators to built-in fields and I'm not sure it's a good idea as they are used elsewhere in the Django core.

I think the best option for you is to define a custom field with the validation already applied, and use it in alternative to CharField, eg:

class FtfyCharField(CharField):
    default_validators = [validate_ftfy]

class Message(models.Model):
    content = FtfyCharField(max_length=1000)

If you wanted to apply it to other types of field you could implement it as a mixin, eg:

class FtfyFieldMixin(models.Field):
    default_validators = [validate_ftfy]

class FtfyCharField(models.CharField, FtfyFieldMixin):
    pass

class FtfyTextField(models.TextField, FtfyFieldMixin):
    pass

Upvotes: 1

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