Django 2 template tag: include_once

include_once.py

from django import template

register = template.Library()


def render_include_once(self, context):
    ctname = '_include_once_node_registry'
    if ctname not in context:
        context[ctname] = {}
    
    if not self.include_path or self.include_path in context[ctname]:
        return ""
    else:
        context[ctname][self.include_path] = True
        return self._render_origin(context)


@register.tag(name='include_once')
def do_include_once(parser, token):
    import types
    from django.template.loader_tags import do_include
    included = do_include(parser, token)
    
    try:
        included.include_path = included.template.var
    except AttributeError:
        included.include_path = None

    included._render_origin = included.render
    included.render = types.MethodType(render_include_once, included)
    return included