max_length validation is not wroking with Modelserializer

[Anshulgoplus]

I created a model have a field as charField and has max_length then i created a model serailzer for that model by the serializer is not validating the field with max_length

class MyModel(models.Model):
name = models.CharField(max_length=255, verbose_name=_("Name"))

class MyModelSerializer(ModelSerializer):
classs Meta:
model=MyModel
fields = "all"

when I send a post request with name as 256 chars it is throwing 500 it should throw 400

[smchougrani]

Hi Anshulgoplus,

Thank you for raising this issue. The problem you described involves the validation of the maximum length of a CharField in a ModelSerializer. When you send a POST request with a name field containing 256 characters, you receive a 500 error instead of the expected 400 error.

Issue Analysis
The issue seems to stem from the ModelSerializer not automatically enforcing the maximum length constraint defined in the model. To resolve this, you can explicitly define the name field in the serializer with the max_length constraint.

Proposed Solution
Here’s how you can modify your serializer to include this validation:

from rest_framework import serializers

class MyModelSerializer(serializers.ModelSerializer):
    name = serializers.CharField(max_length=255)

    class Meta:
        model = MyModel
        fields = '__all__'

Explanation
By explicitly defining the name field in the serializer with max_length=255, you ensure that the maximum length validation is applied when the data is deserialized. This will raise a ValidationError if the length of the string exceeds 255 characters, resulting in a 400 error instead of a 500 error.

Conclusion
This solution should resolve the issue without requiring changes to the core framework. If you have any further questions or encounter other issues, please feel free to share them.

Thank you again for your contribution!

Best regards,
Chougrani Sidi Mohammed

[humayunah]

@Anshulgoplus I can't seem to replicate this issue with the latest version of djangorestframework and without explicitly defining the name field in the serializer as suggested above, I got the following validation error with status code 400.

{
    "name": [
        "Ensure this field has no more than 255 characters."
    ]
}

[smchougrani]

Hi @Anshulgoplus,

Thank you for your prompt feedback. It's great to hear that you couldn't replicate the issue with the latest version of Django REST Framework and that the validation error is being correctly handled with a status code 400.