Stricter type validation for CharField.

[lovelydinosaur]

CharField now only accepts string and numeric types, and will raise a validation error on other inputs.

Closes #3394.

[michael-k]

Breaking change + minor version update 💥
But now we know about the issue in our code, .i.e. “eg. unclear if booleans should represent as true or True”.

[lovelydinosaur]

Noted.

I'd treated it as not a breaking change, given that it'd only be exposed in already broken use-cases. (eg clients posting booleans to a CharField)

Still, it's evidently worth us being more conservative in the future, given the large installed base, now. Thanks for the data-point.

[sergiomb2]

How I override ? :

    if isinstance(data, bool) or not isinstance(data, six.string_types + six.integer_types + (float,)):

with

    if isinstance(data, bool) or not isinstance(data, six.string_types):

I don't want integers or floats be consider as a valid string .

Thanks

[michael-k]

@sergiomb2 Derive a new class from CharField. Override to_internal_value by either copying the implementation and changing it, or by first performing your stricter check and then calling the parent's method.

Possibility 1:

class MyCharField(CharField):
    def to_internal_value(self, data):
        if isinstance(data, bool) or not isinstance(data, six.string_types):
            self.fail('invalid')
        value = six.text_type(data)
        return value.strip() if self.trim_whitespace else value

Possibility 2:

class MyCharField(CharField):
    def to_internal_value(self, data):
        if isinstance(data, bool) or not isinstance(data, six.string_types):
            self.fail('invalid')
        return super().to_internal_value(data)  # python 3 syntax

Do not forget to use your field in your serializers.

If you're using the ModelSerializer, you can derive from it and adjust serializer_field_mapping.

[sergiomb2]

many thanks, yes I already use Possibility 1 , but Possibility 2 looks to me even better .
yes I already added this code (and to complete the example) :

from rest_framework import serializers 
from rest_framework.serializers import CharField

class CustomSerializer(serializers.ModelSerializer):
    user_name = MyCharField(max_length=45)

If you're using the ModelSerializer, you can derive from it and adjust serializer_field_mapping.

Could you exemplify what you mean ? I think will much more easy to me understand, yes I'd like override all CharFields in the project with MyCharField options , do I need reference all CharField in Serializers class ?

Many thanks for the feedback

[michael-k]

class MyModelSerializer(ModelSerializer):
    serializer_field_mapping = {
        models.AutoField: IntegerField,
        models.BigIntegerField: IntegerField,
        models.BooleanField: BooleanField,
        models.CharField: MyCharField,  # ← see here
        models.CommaSeparatedIntegerField: MyCharField,  # ← see here
        models.DateField: DateField,
        models.DateTimeField: DateTimeField,
        models.DecimalField: DecimalField,
        models.EmailField: EmailField,
        models.Field: ModelField,
        models.FileField: FileField,
        models.FloatField: FloatField,
        models.ImageField: ImageField,
        models.IntegerField: IntegerField,
        models.NullBooleanField: NullBooleanField,
        models.PositiveIntegerField: IntegerField,
        models.PositiveSmallIntegerField: IntegerField,
        models.SlugField: SlugField,
        models.SmallIntegerField: IntegerField,
        models.TextField: MyCharField,  # ← see here
        models.TimeField: TimeField,
        models.URLField: URLField,
        models.GenericIPAddressField: IPAddressField,
        models.FilePathField: FilePathField,
    }

Then use MyModelSerializer instead.

[sergiomb2]

Thanks , exemplifying a more complete solution :

class CharField_stricter(serializers.CharField):
    def to_internal_value(self, data):
        if isinstance(data, bool) or not isinstance(data, six.string_types):
            self.fail('invalid')
        value = six.text_type(data)
        return value.strip() if self.trim_whitespace else value

class ModelSerializer_stricter(serializers.ModelSerializer):
    serializer_field_mapping = serializers.ModelSerializer.serializer_field_mapping.copy()
    serializer_field_mapping.update({
         models.CharField: CharField_stricter
    })

class FooSerializer(ModelSerializer_stricter):