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
35493	Allow `./` and `../` in paths when recursively including templates	Gabriel Nick Pivovarov	nobody	"Hi. Currently, when trying to recursively include a Django template within itself using the `include` tag with a path that contains `./` or `../`, Django raises a `TemplateSyntaxError`. However, using a path that does not contain `./` or `../` does not raise the error. When the error is raised, the debug toolbar describes it like this:

> = TemplateSyntaxError at /
>
> The relative path ‘“./ul.html”’ was translated to template name ‘app/ul.html’, the same template in which the tag appears.

Here is an example of a template in a Django app called `app` with the path `app/templates/app/ul.html` that would produce the error given above:

{{{
<ul>
    {% for section in sections %}
        <li>
            <p>{{ section.name }}</p>
            {% if section.sections|length != 0 %}
                {% include ""./ul.html"" with sections=section.sections %}
            {% endif %}
        </li>
    {% endfor %}
</ul>
}}}

However, replacing the directory `./ul.html` with the equivalent `app/ul.html` makes the error go away (assuming that the project's `settings.py` specifies `APP_DIRS = True` and the views and URLs are configured correctly). The actual paths are translated identically in both cases, and the behavior of the `include` tag should not depend simply on whether or not the path string uses `./` or `../` (or if it should, this is not documented in the Django documentation). Therefore, it seems that this is a bug. The expected behavior is that an error is only raised when recursively using the `extends` template, not when recursively using the `include` template.

Contrapositively, it appears that recursively extending a template using the `extends` tag with a path that does ''not'' contain `./` or `../` raises a `TemplateDoesNotExist` exception.

One possible fix is to modify the `django/template/loader_tags.py` file (https://github.com/django/django/blob/main/django/template/loader_tags.py) such that the error is raised when a template attempts to extend itself (not when a template attempts to include itself, which would otherwise be valid). The error handling logic in question starts on line 267 of that file within the `construct_relative_path` function; perhaps it should live somewhere in the `do_extends` function instead.

Here is a relevant discussion in the Django forums: https://forum.djangoproject.com/t/template-recursion-why-does-django-not-allow-and/31689"	Bug	new	Template system	5.0	Normal		template		Unreviewed	0	0	0	0	1	0