Calling block inside an if condition: django template

Question

I have been trying to call a block inside an if condition in django template.

I have a base template. I have many other templates that extend the base template. I have defined a block in base template:

{% block test_block %}Test{% endblock %}

I then want to override this block on a certain condition in the other templates. If the condition fails, the block shouldn't get overridden. This is something what I have written:

{% if test_value %}{% block test_block %}Development{% endblock %}{% endif %}

This actually (or may be virtually) ignores the if condition.

What I finally did:

{% block test_block %}{% if test_value %}Development{% else %}{{ block.super }}{% endif %}{% endblock %}

I had to do something like this everywhere it was required.

Is this the best way? Is this the only way? Why can't I try the first way of mine? Or is there any mistake from my side?

Answer 1

You haven't made a mistake - template blocks are included regardless of any conditionals around them. You can see this from this line of the ExtendsNode class of django/template/loader_tags.py in the Django source code:

self.blocks = {n.name: n for n in nodelist.get_nodes_by_type(BlockNode)]}

When the {% extends %} is being rendered, it fetches all block nodes from the template directly and stores them for rendering when the parent comes across those blocks. Whether those blocks in the child were inside conditionals or not isn't considered.