Add conditional expressions to block tag

[Markus Amalthea Magnuson]

It would be nice if I could add a conditional expression after a block name, mimicking the shortcut conditional expression form in Python, to only render a block if a certain condition is true. So instead of writing e.g. this:

{% block title %}
  {% if post.title %}
    {{ post.title }}
  {% else %}
    {{ block.super }}
  {% endif %}
{% endblock %}

I could write this:

{% block title if post.title %}My title{% endif%}

See also #9173 (comment 9) where I first thought of this.

I have some working proof of concept code and could open a pull request to start working on this, if accepted.

[Tim Graham]

How is this different from #9173? I suggest to write to the DevelopersMailingList to get feedback on your proposal.

[Markus Amalthea Magnuson]

#9173 is for rendering a block only if a child template also defines that block and has some content in it.

This ticket is for the more general usage of rendering a block only if some condition is true. We cannot currently put {% block %} tags inside {% if %} tags, and this would solve that.

(Or rather, we can do that, but the block will always be rendered.)

[Tim Graham]

Closing this particular solution based on the mailing list discussion, although it seems like there might be some improvement in this area that could be done.
​https://groups.google.com/d/msg/django-developers/myj8aEcVMt4/0bAITiexTCcJ