Error when trying to do django runserver -> pydantic.errors.PydanticSchemaGenerationError

[93Deepak]

Describe the bug
I have django models

#models.py

class ClassDetail(models.Model):
    class_name = models.CharField(max_length=50)

    def __str__(self):
        return self.class_name


class Student(models.Model):
    first_name = models.CharField(max_length=50)
    last_name = models.CharField(max_length=50)
    full_name = models.CharField(max_length=100)
    classs = models.ForeignKey(ClassDetail, on_delete=models.CASCADE)
    created_at = models.DateTimeField(auto_now=True)
    updated_at = models.DateTimeField(auto_now_add=True)

    def save(self, *args, **kwargs):
        self.full_name = self.first_name + " " + self.full_name
        super(Student, self).save(*args, **kwargs)

and Ninja Schema

#Schema.py

from ninja import ModelSchema
from .models import ClassDetail, Student

class ClassSchema(ModelSchema):
    class Config:
        model = ClassDetail
        model_fields = "__all__"
        arbitrary_types_allowed=True


class StudentSchema(ModelSchema):
    classs: ClassSchema
    class Config:
        model = Student
        model_fields = '__all__'
   

and api routes

#api.py

from typing import List
from ninja import Router

from .models import Student, ClassDetail
from .schema import ClassSchema, StudentSchema

router = Router()

@router.post('/class', response=ClassSchema)
def create_clas(request, payload=ClassSchema):
    clas = ClassDetail.objects.create(**payload.dict())
    return clas

@router.get('/student', response=List[StudentSchema])
def get_students(request):
    schema = Student.objects.all()
    return schema


@router.post('/student', response=StudentSchema)
def create_student(request, payload: StudentSchema):
    stu = Student.objects.create(**payload.dict())
    return stu

when trying to run the server i am getting this error

pydantic.errors.PydanticSchemaGenerationError: Unable to generate pydantic-core schema for <class 'ninja.orm.metaclass.ModelSchemaMetaclass'>. Set `arbitrary_types_allowed=True` in the model_config to ignore this error or implement `__get_pydantic_core_schema__` on your type to fully support it.

If you got this error by calling handler(<some type>) within `__get_pydantic_core_schema__` then you likely need to call `handler.generate_schema(<some type>)` since we do not call `__get_pydantic_core_schema__` on `<some type>` otherwise to avoid infinite recursion.

Versions

• Python version: [3.9]
• Django version: [5.0.4]
• Django-Ninja version: [1.1.0]
• Pydantic version: [2.7.1]
• pydantic core version: [2.18.2]

[JFeldaca]

Missing return in save def method.

#models.py

class Student(models.Model):
    [...]
    def save(self, *args, **kwargs):
        student = super(Student, self).save(*args, **kwargs)
        student.full_name = f"{student.first_name} {student.last_name}"
        student.save()
        return student

Alternative:

#models.py

class Student(models.Model):
    [...]
    def save(self, *args, **kwargs):
        student = super(Student, self).save(*args, **kwargs)
        student.full_name = student.first_name + " " + student.full_name 
        student.save()
        return student

In your original code you have self.full_name when it should be self.last_name