Jinja 2 : escaping and extending - django-templates

Question

I am trying to output html after running my templates through Jinja2 and thereafter through Django. The {{ 'RAW' }} and {% raw %}...{% endraw %} tags are not doing what I expect then to and there is not a lot of documentation on this nor does my googling yield anything helpful.
As an example consider the following series of templates. The first is a stock Jinja2 base page which one wants to extend.
{# jinja_base.html #}
{% block jinja_head %}
JINJA HEAD
{% endblock jinja_head %}
{% block jinja_body %}
JINJA BODY
{% endblock jinja_body %}
{% block jinja_foot %}
JINJA FOOT
{% endblock jinja_foot %}
The second is a stock Django template page that one wants to extend.
{# django_base.html #}
{% block django_head %}
DJANGO HEAD
{% endblock django_head %}
{% block django_body %}
DJANGO BODY
{% endblock django_body %}
{% block django_foot %}
DJANGO FOOT
{% endblock django_foot %}
To extend both of them I have a Jinja/Django mixin template that reads as follows. The idea is to run it through Jinja first then through Django.
{# mixin.html #}
{{ '{% extends "django_base.html" %}' }}
{% extends "jinja_base.html" %}
{{ '{% block django_head %}' }}
{% block jinja_head %}
MIXIN HEAD
{% endblock jinja_head %}
{{ '{% endblock django_head %}' }}
{{ '{% block django_body %}' }}
{% block jinja_body %}
MIXIN BODY
{% endblock jinja_body %}
{{ '{% endblock django_body %}' }}
{{ '{% block django_foot %}' }}
{% block jinja_foot %}
JINJA FOOT
{% endblock jinja_foot %}
{{ '{% endblock django_foot %}' }}
After the Jinja run, I'm expecting the following output
{% extends "django_base.html" %}
{% block django_head %}
MIXIN HEAD
{% endblock django_head %}
{% block django_body %}
MIXIN BODY
{% endblock django_body %}
{% block django_foot %}
JINJA FOOT
{% endblock django_foot %}
however, I am getting the following instead.
{% extends "jinja_base.html" %}
MIXIN HEAD
MIXIN BODY
JINJA FOOT
That is all the Django code which is embedded in the Jinja escape sequences is getting stripped. The first tag however is retained.
The docs mention that anything before an extends is kept as is but that everything after is not. There is no explanation on how best to circumvent this nor why this affects raw/escaped code.
Hmm.. perhaps I must place the extends right at the end ?

Answer 1

After you extend a template you have to put the content between blocks. Every other stuff is ignored. So in the mixin.html:
{{ '{% block django_head %}' }} <--- ignored
{% block jinja_head %}
MIXIN HEAD
{% endblock jinja_head %}
{{ '{% endblock django_head %}' }} <--- ignored
The first and the last line are outside of the jinja_head block, thus will be ignored.
The correct way is straightforward, just put the Django lines between Jinja's blocks, e.g.:
{% block jinja_head %}
{{ '{% block django_head %}' }}
MIXIN HEAD
{{ '{% endblock django_head %}' }}
{% endblock jinja_head %}
This results:
{% block django_head %}
MIXIN HEAD
{% endblock django_head %}
For the {{ '{% extends "django_base.html" %}' }} just define an empty block in jinja_base.html, which you can override in the mixin.html with the Django extends line. The complete example:
jinja_base.html
{# jinja_base.html #}
{% block django_extends %}
{% endblock django_extends %}
{% block jinja_head %}
JINJA HEAD
{% endblock jinja_head %}
{% block jinja_body %}
JINJA BODY
{% endblock jinja_body %}
{% block jinja_foot %}
JINJA FOOT
{% endblock jinja_foot %}
mixin.html
{# mixin.html #}
{% extends "jinja_base.html" %}
{% block django_extends %}
{{ '{% extends "django_base.html" %}' }}
{% endblock django_extends %}
{% block jinja_head %}
{{ '{% block django_head %}' }}
MIXIN HEAD
{{ '{% endblock django_head %}' }}
{% endblock jinja_head %}
{% block jinja_body %}
{{ '{% block django_body %}' }}
MIXIN BODY
{{ '{% endblock django_body %}' }}
{% endblock jinja_body %}
{% block jinja_foot %}
{{ '{% block django_foot %}' }}
JINJA FOOT
{{ '{% endblock django_foot %}' }}
{% endblock jinja_foot %}
This way you will see the expected result after Jinja's render:
{% extends "django_base.html" %}
{% block django_head %}
MIXIN HEAD
{% endblock django_head %}
{% block django_body %}
MIXIN BODY
{% endblock django_body %}
{% block django_foot %}
JINJA FOOT
{% endblock django_foot %}