Show object description and a link next to django's raw_id_fields, for ForeignKey and ManyToMany fields

admin_raw_id.py

"""
Show customisable str representation of the linked objects next to each raw id
field in a django admin change form. Works for ForeignKey, OneToOneField, and
ManyToManyField fields.

Example:

    from django.contrib import admin
    from admin_raw_id import ImprovedRawIdFieldsAdmin
    from .models import MyModel

    @admin.register(MyModel)
    class MyModelAdmin(ImprovedRawIdFieldsAdmin):
        ...


Inspired by https://djangosnippets.org/snippets/2217/
"""

from django.contrib import admin
from django.contrib.admin.sites import site
from django.contrib.admin.widgets import ManyToManyRawIdWidget, \
    ForeignKeyRawIdWidget
from django.core.urlresolvers import reverse
from django.utils.html import escape


class VerboseForeignKeyRawIdWidget(ForeignKeyRawIdWidget):
    """Shows customisable str representation of the linked object next to the
       raw id field for a ForeignKey or OneToOneField in a django admin change
       form. To customise pass get_str as a keyword argument when initialising
       the widget.
    """

    def __init__(self, *args, **kwargs):
        self.get_str = kwargs.pop('get_str', str)
        super(VerboseForeignKeyRawIdWidget, self).__init__(*args, **kwargs)

    def label_for_value(self, value):
        key = self.rel.get_related_field().name
        try:
            obj = self.rel.to._default_manager.using(
                self.db).get(**{key: value})
        except (ValueError, self.rel.to.DoesNotExist):
            return '???'

        change_url = reverse(
            "admin:%s_%s_change" % (obj._meta.app_label,
                                    obj._meta.object_name.lower()),
            args=(obj.pk,)
        )
        return '&nbsp;<strong><a href="%s">%s</a></strong>' % (
            change_url, escape(self.get_str(obj)))


class VerboseManyToManyRawIdWidget(ManyToManyRawIdWidget):
    """Shows customisable str representation of the linked object next to the
       raw id field for a ManyToManyField in a django admin change form. To
       customise pass get_str as a keyword argument when initialising the
       widget.
    """

    def __init__(self, *args, **kwargs):
        self.get_str = kwargs.pop('get_str', str)
        super(VerboseManyToManyRawIdWidget, self).__init__(*args, **kwargs)

    def label_for_value(self, value):
        values = value.split(',')
        str_values = []
        key = self.rel.get_related_field().name
        for v in values:
            try:
                obj = self.rel.to._default_manager.using(self.db).get(
                    **{key: v})
            except self.rel.to.DoesNotExist:
                str_values += ['???']
            else:
                change_url = reverse(
                    "admin:%s_%s_change" % (obj._meta.app_label,
                                            obj._meta.object_name.lower()),
                    args=(obj.pk,)
                )
                str_values += ['<strong><a href="%s">%s</a></strong>' % (
                    change_url, escape(self.get_str(obj)))]
        return ', '.join(str_values)


class ImprovedRawIdFieldsAdmin(admin.ModelAdmin):
    def formfield_for_dbfield(self, db_field, **kwargs):
        if db_field.name in self.raw_id_fields:
            kwargs.pop("request", None)
            rel_type = db_field.rel.__class__.__name__
            if rel_type == "ManyToManyRel":
                kwargs['widget'] = VerboseManyToManyRawIdWidget(
                    db_field.rel, site)
            else:
                # assume it's a ManyToOneRel or OneToOneRel
                kwargs['widget'] = VerboseForeignKeyRawIdWidget(
                    db_field.rel, site)
            return db_field.formfield(**kwargs)
        return super(ImprovedRawIdFieldsAdmin, self).formfield_for_dbfield(
            db_field, **kwargs)