Cascade on ForeignKey

Description

This check ensures that ForeignKey fields are not using the CASCADE option for the on_delete parameter and raises a warning about potential data loss.

Rationale

Using CASCADE for the on_delete parameter in ForeignKey fields can lead to unexpected data loss when the referenced object is deleted. While it may be appropriate in some cases, other options like SET_NULL or PROTECT can be safer alternatives depending on the application's requirements.

Example

Consider the following model:

from django.db import models

class Author(models.Model):
    name = models.CharField(max_length=100)

class Book(models.Model):
    title = models.CharField(max_length=100)
    author = models.ForeignKey(Author, on_delete=models.CASCADE)

The author field is a ForeignKey field and is using the CASCADE option for on_delete. The check would detect this and recommend considering alternative options:

author = models.ForeignKey(Author, on_delete=models.SET_NULL, null=True)
# or
author = models.ForeignKey(Author, on_delete=models.PROTECT)

Evaluate the impact of using CASCADE on your application's data integrity and choose the appropriate option based on your specific use case.