Template tag to rerender a block

reblock.py

from django import template
from django.template.loader import get_template
from django.template.loader_tags import BlockNode, ExtendsNode

register = template.Library()

@register.simple_tag(takes_context=True)
def reblock(context, block_name):
    """
    Renders a specific block from the current template or its parent templates.
    :param context: The current template context.
    :param block_name: The name of the block to render.

    Usage:
        {% load reblock %}
        ...
        <h1>{% block title %}Default Title{% endblock %}</h1>
        
        {% reblock "title" %}
        
        ...
    """
    # Helper function to find block nodes in the template
    def find_block(nodelist, block_name):
        for node in nodelist:
            if isinstance(node, BlockNode) and node.name == block_name:
                return node
            if hasattr(node, 'nodelist'):
                found = find_block(node.nodelist, block_name)
                if found:
                    return found
        return None

    # Traverse the template tree to find the block
    template_instance = context.template
    while template_instance:
        block = find_block(template_instance.nodelist, block_name)
        if block:
            return block.render(context)
        
        # Move to the parent template
        try:
            extends_node = next((node for node in template_instance.nodelist.get_nodes_by_type(ExtendsNode)), None)
            if extends_node:
                # Use the template loader to fetch the parent template
                parent_template_name = extends_node.parent_name.resolve(context)
                parent_template = get_template(parent_template_name)
                template_instance = parent_template.template
            else:
                break
        except Exception as e:
            raise ValueError(f"Error resolving parent template: {e}")

    raise ValueError(f"Block '{block_name}' not found in the template hierarchy.")