id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
32364	ModelAdmin.formfield_overrides drops TEMPLATES...DIRS while loading a custom widget template within a std admin form template	zoltan-ky	nobody	"Using Django 3.1.5.  This custom widget ""idea"" is a minimal demo-version based on https://docs.djangoproject.com/en/3.1/ref/contrib/admin/#django.contrib.admin.ModelAdmin.formfield_overrides.

So I'd like to use a MyTextArea widget with its mytextarea.html  on models.TextField (myapp.Post.body) below and use it to edit Posts within the admin. (I know how to do it through forms, creating my form fields *and* my widgets, but that's a workaround).

When I 'runserver' and try to add a new Post under the admin a ""django.template.exceptions.TemplateDoesNotExist: myapp/mytextarea.html"" exception is thrown.

What am I missing in the test setup below?

I have traced the problem, as it is set up, (using pdb) to the EngineMixin class (django/forms/renderer.py:39) which has a 'hard-coded'  backend ' named 'djangoforms'.   This DjangoTemplates instance used to instantiate MyTextArea is **different** from the one used to find the admin form template.    Somewhere, and I don't understand enough of what's going on here, the 'dirs' property of the first Engine (used for the form template) gets dropped and not passed to the Engine used to load the custom widget template.

To recreate (django 3.1.5): starting with a new:  django-admin startproject myproject;  ... startapp myapp.  After creating the few small files below, migrate, createsuperuser for admin.

In the startproject-created  *myproject/myproject/settings.py* the only changes are:
* 'myapp' is added to INSTALLED_APPS 
* TEMPLATES...DIRS: [ BASE_DIR / 'templates' ],
to use project-wide templates.

The files:
**myapp/admin.py**:
{{{
from django.contrib import admin
from django.db import models
from myapp.models import Post
from myapp.widgets import MyTextWidget
# Register your models here.
class PostAdmin(admin.ModelAdmin):
    formfield_overrides = {
        models.TextField: {'widget': MyTextWidget}
    }
admin.site.register(Post, PostAdmin)
}}}

**myapp/models.py**:
{{{
from django.db import models
# Create your models here.
class Post(models.Model):
    body = models.TextField()
}}}

**myapp/widgets.py:**
{{{
from django import forms
from django.contrib.admin import widgets
class MyTextWidget(forms.Textarea):
    template_name = 'myapp/mytextarea.html'
}}}

<project>**/templates/myapp/mytextarea.html**:
{{{
{# based on django/forms/templates/django/forms/widgets/textarea.html #}
<textarea name=""{{ widget.name }}""{% include ""django/forms/widgets/attrs.html"" %}>
<p>MY TEXTAREA</p>
{% if widget.value %}{{ widget.value }}{% endif %}</textarea>
}}}

"	Uncategorized	closed	Template system	3.1	Normal	worksforme	formfield_overrides		Unreviewed	0	1	0	0	0	0