django-eav-json-fields 0.1.0

Schema-validated JSONFields for Django using an EAV-style DSL

django-eav-json-fields

Schema-validated JSONFields for Django using an EAV-style DSL.

Define expected keys, types, and constraints on JSON dict values stored in Django JSONFields. Storage remains plain JSONB in PostgreSQL -- the EAV layer adds validation, type coercion, and admin widgets.

Requirements

• Python 3.10+
• Django 4.2+

Installation

pip install django-eav-json-fields

No INSTALLED_APPS entry is needed.

Quick Start

Define a schema

from eav_fields import EAVSchema, EAVBoolean, EAVString, EAVDecimal, EAVInteger

class ServiceConfig(EAVSchema):
    enabled = EAVBoolean(default=True, help_text="Enable this service")
    label = EAVString(max_length=100, help_text="Display name")
    price = EAVDecimal(required=False, max_digits=10, decimal_places=2)
    max_retries = EAVInteger(min_value=0, max_value=10, default=3, required=False)

Use EAVField on a model

from django.db import models
from eav_fields import EAVField

class Service(models.Model):
    name = models.CharField(max_length=100)
    config = EAVField(schema=ServiceConfig)

The field validates during full_clean() that the JSON dict conforms to the schema. Unknown keys are rejected, types are coerced, and constraints are enforced.

Polymorphic schemas

Select a schema based on another field's value:

class Product(models.Model):
    product_type = models.CharField(max_length=20, choices=[("a", "Type A"), ("b", "Type B")])
    config = EAVField(
        schema_map={"a": SchemaA, "b": SchemaB},
        schema_key_field="product_type",
    )

EAV Attribute Types

Type	Python Type	JSON Storage	Constraints
EAVString	str	string	max_length, choices
EAVBoolean	bool	boolean	--
EAVInteger	int	number	min_value, max_value, choices
EAVFloat	float	number	min_value, max_value, choices
EAVDecimal	Decimal	string	max_digits, decimal_places, min_value, max_value, choices

All attributes support: required (default True), default, help_text, choices.

Cross-field Validation

Override validate_cross for rules spanning multiple attributes:

from django.core.exceptions import ValidationError
from eav_fields import EAVSchema, EAVInteger

class MyConfig(EAVSchema):
    min_val = EAVInteger()
    max_val = EAVInteger()

    @classmethod
    def validate_cross(cls, data):
        if data.get("min_val", 0) >= data.get("max_val", 0):
            raise ValidationError({"max_val": ["max_val must be greater than min_val."]})

Schema Inheritance

Child schemas inherit parent attributes and can override them:

class BaseConfig(EAVSchema):
    name = EAVString()

class ExtendedConfig(BaseConfig):
    count = EAVInteger()  # inherits 'name' from parent

Admin Widget

EAVField automatically provides an EAVWidget in the Django admin that renders typed HTML inputs for each schema attribute, with show/hide support for polymorphic schemas.

Migration Support

Schema references are serialized as dotted import paths in migrations. Both class references and string paths are accepted:

# Both are equivalent:
config = EAVField(schema=MySchema)
config = EAVField(schema="myapp.schemas.MySchema")

License

MIT