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Simplifies the use of function attributes for the django admin and makes mypy happy

Project description

django-admin-display

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Simplifies the use of function attributes (eg. short_description) for the django admin and makes mypy happy :)

Requirements

  • Python >= 3.6
  • Django >= 1.11

Usage

If you want to change the behaviour of how Django displays a read-only value in the admin interface, you can add some special attributes to the corresponding method. Supported values are

short_description
Customize the column’s title of the callable.

empty_value_display
Show this value instead, if the value of a field is None, an empty string, or an iterable without elements.

admin_order_field
Indicate that the value is represented by a certain database field.

boolean
Display a pretty “on” or “off” icon if the method returns a boolean.

allow_tags (deprecated since Django 1.9)
Disable auto-escaping.

The following example shows, how you normally apply these attributes to an AdminModel or a Model method.

class Company(models.Model):
    ...

    def owner(self) -> bool:
        return self.owner.last_name
    is_valid.short_description = "Company owner"
    is_valid.admin_order_field = 'owner__last_name'

This module replaces the way of defining these attributes by providing a handy decorator.

from django_admin_display import admin_display


class Company(models.Model):
    ...

    @admin_display(
        short_description="Company owner",
        admin_order_field='owner__last_name',
    )
    def owner(self) -> bool:
        return self.owner.last_name

Why?

There are mainly two reasons why this module exists.

Usage with @property

It is quite common that a calculated model property is displayed in the admin interface:

class Company(models.Model):
    ...

    @property
    def created_on(self) -> datetime.date:
        return self.created_at.date()

In order to add special attributes, you have to create a protected method, attach the attributes and wrap that method using property()

class Company(models.Model):
    ...

    def _created_on(self) -> datetime.date:
        return self.created_at.date()
    _created_on.short_description = "Created on"
    created_on = property(_created_on)

This is quite cumbersome, hard to read and most people don't know that this is even possible. To overcome these downsides you can achieve the same result using the @admin_diplay decorator.

from django_admin_display import admin_display


class Company(models.Model):
    ...

    @property
    @admin_display(
        short_description = "Created on",
    )
    def created_on(self) -> datetime.date:
        return self.created_at.date()

mypy

If you are using mypy, you have probably stumbled over an error similar to this one

"Callable[[Any, Any], Any]" has no attribute "short_description"

A common solution is to ignore the type checking by adding # type: ignore to the end of the line.

class CompanyAdmin(admin.ModelAdmin):
    ...

    def created_on(self, company: models.Company) -> datetime.date:
        return company.created_at.date()
    created_on.short_description = "Created on"  # type: ignore

The issue is already known and heavily discussed on github.

This decorator solves the issue by internally using # type: ignore and providing a well-defined signature for setting the attributes. It is not an optimal solution but works well until the issue has been resolved.

Development

This project is using poetry to manage all dev dependencies. Clone this repository and run

  poetry install
  poetry run pip install Django

to create a virtual environment with all dependencies. You can now run the test suite using

  poetry run pytest

This repository follows the angular commit conventions.

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