Assets template tag

assets2.py

# We currently use webassets for asset bundling. Unfortunately it
# requires you to write lengthy tag definitions in HTML:
#
#   {% load assets %}
#   {% assets "foo_js", "bar_js" %}
#     <script type="text/javascript" src="{{ ASSET_URL }}"></script>
#   {% endassets %}
#
# This tag simplifes the above:
#
#   {% load assets2 %}
#   {% assetsjs "foo", "bar" %}
#
# Ta-da!
#
# Some discussion here: https://github.com/miracle2k/webassets/issues/26

import re

from django.template import Library
from django.template import Node
from django.template import Template
from django.template import TemplateSyntaxError


register = Library()


class BaseAssetNode(Node):

    suffix = None
    html = None

    def __init__(self, names):
        self.names = names

    def render(self, context):
        names = ', '.join('"%s%s"' % (name, self.suffix) for name in self.names)
        html  = ("{%% load assets %%}"
                 "{%% assets %s %%} %s {%% endassets %%}" % (names, self.html))
        print 'RENDER', html
        return Template(html).render(context)


class JSAssetNode(BaseAssetNode):
    suffix = '_js'
    html = '<script type="text/javascript">{% ASSET_URL %}</script>'


class CSSAssetNode(BaseAssetNode):
    suffix = '_css'
    html = '<link rel="stylesheet" type="text/css" href="{{ ASSET_URL }}"/>'


def generate_tag_handler(klass):
    """
    Returns a tag-rendering function which uses one of the above classes.

    See https://docs.djangoproject.com/en/dev/howto/custom-template-tags/
    """
    # A regex to match surrounding quotes.
    quoted_re = re.compile(r''' ^ ["'] ([^"']+) ["'] $ ''', re.X)

    def handler(parser, token):
        try:
            names = token.split_contents()[1:]
        except (ValueError, IndexError):
            raise TemplateSyntaxError('%r tag requires bundle names',
                                      token.contents.split()[0])
        def clean(name):
            # Might be a trailing comma after the bundle name.
            if name[-1] == ',':
                name = name[:-1]

            # Remove surrounding quotes if any.
            match = quoted_re.match(name)
            if match:
                name = match.group(1)

            # Check for programmer error.
            if name.endswith(klass.suffix):
                raise TemplateSyntaxError(
                    'Remove the "%s" suffix from asset bundle '
                    '"%s" -- not necessary when using the %s tag'
                    % (klass.suffix, name, token.contents.split()[0]))

            return name

        names = [clean(name) for name in names]
        print 'names=', names
        return klass(names)

    return handler

register.tag('assets_js', generate_tag_handler(JSAssetNode))
register.tag('assets_css', generate_tag_handler(CSSAssetNode))

Any chance of jinja version of this tag? :)

No time, I'm afraid :)

(This is pretty cheesy, anyway. I'm sure I could do something smarter than creating a template macro.)