django-permissionedforms

django-permissionedforms

django-permissionedforms is an extension to Django's forms framework, allowing you to define forms where certain fields are shown or omitted according to the user's permissions.

Installation

Run: pip install django-permissionedforms

Usage

To add permission rules to a basic Django form, subclass permissionedforms.PermissionedForm in place of django.forms.Form and add an inner Meta class:

from permissionedforms import PermissionedForm

class PersonForm(PermissionedForm):
    first_name = forms.CharField()
    last_name = forms.CharField()

    class Meta:
        field_permissions = {
            'last_name': 'myapp.change_last_name'
        }

field_permissions is a dict, mapping field names to permission codenames. For each field listed, that field will only be included in the final form if the user has the specified permission, as defined by the user.has_perm() method. See Django's documentation on custom permissions and programmatically creating permissions for details on how to set permissions up; alternatively, if you want to set a field as only available to superusers, you can use any arbitrary string (such as 'superuser') as the codename, since has_perm always returns True for them.

Then, when instantiating the form, pass the keyword argument for_user:

form = PersonForm(for_user=request.user)

This will result in a form where the last_name field is only present if the logged-in user has the change_last_name permission.

The keyword argument for_user is optional, and if not passed, the form will behave as an ordinary form with all named fields available.

For a ModelForm, the procedure is the same, except that you should inherit from permissionedforms.PermissionedModelForm instead. field_permissions is added alongside the existing Meta options:

from permissionedforms import PermissionedModelForm

class CountryForm(PermissionedModelForm):
    class Meta:
        model = Country
        fields = ['name', 'description']
        field_permissions = {
            'description': 'tests.change_country_description'
        }

form = CountryForm(instance=country, for_user=request.user)

Integrating with other base form classes

You may wish to integrate the permission handling from django-permissionedforms into some other base form class, such as ClusterForm from the django-modelcluster package. If that base form class is a straightforward subclass of django.forms.Form or django.forms.ModelForm, then using multiple inheritance to additionally inherit from PermissionedForm or PermissionedModelForm should work:

from fancyforms import FancyForm  # made up for example purposes
from permissionedforms import PermissionedForm

class FancyPermissionedForm(PermissionedForm, FancyForm):
    pass

However, this will fail if the base form class implements its own metaclass. In this case, you will need to define a new metaclass inheriting from both the existing one and permissionedforms.PermissionedFormMetaclass:

from fancyforms import FancyForm
from permissionedforms import PermissionedForm, PermissionedFormMetaclass


FancyFormMetaclass = type(FancyForm)


class FancyPermissionedFormMetaclass(PermissionedFormMetaclass, FancyFormMetaclass):
    pass


class FancyPermissionedForm(PermissionedForm, FancyForm, metaclass=FancyPermissionedFormMetaclass):
    pass

This could still fail if the base form class incorporates a custom Options class to allow it to accept its own class Meta options. If so, it will be necessary to define a new Options class, again using multiple inheritance to subclass both the existing Options class and permissionedforms.PermissionedFormOptionsMixin, and then set this as options_class on the metaclass. The following recipe will work for ClusterForm:

from modelcluster.forms import ClusterForm, ClusterFormMetaclass, ClusterFormOptions
from permissionedforms import PermissionedForm, PermissionedFormMetaclass, PermissionedFormOptionsMixin


class PermissionedClusterFormOptions(PermissionedFormOptionsMixin, ClusterFormOptions):
    pass


class PermissionedClusterFormMetaclass(PermissionedFormMetaclass, ClusterFormMetaclass):
    options_class = PermissionedClusterFormOptions


class PermissionedClusterForm(PermissionedForm, ClusterForm, metaclass=PermissionedClusterFormMetaclass):
    pass

Acknowledgements

django-permissionedforms was developed as part of Wagtail's next-generation page editor, sponsored by Google.