Alternative to flask-webassets w/ autogenerated outfiles via simple jinja2 global

mypage.html

This is a page.

/* Some JS assets */
{{ assets(
    'js/test.js', 'js/device.js',
filters='jsmin', extension='js') }}

/* Some CSS assets */
{{ assets(
    'css/blah.css', 'css/print.css',
extension='css', rel='print') }}

templates.py

# An alternative to flask-webassets which auto-generates out-file names based on the input files
# assumes that your flask.Application.static_url_path = '/inc'
# and that your flask.Application.static_path = 'static'
# and the webassets.Environment is created with args ('', '/inc')

from os import path
from itertools import chain
from hashlib import md5

from flask import Markup
from webassets import Bundle

# app = flask Application
# assets = webassets Environment
from app import app, assets


# Sadly webassets has no way to auto-generate outfile names
def bundle_assets(*files, **options):
    extension = options.pop('extension', '')
    filters = options.pop('filters', [])
    # For css
    rel = options.pop('rel', 'screen')

    # Debug? just print out the file includes
    if assets.debug:
        files = ['/'.join(['inc', f]) for f in files]
        if extension == 'js':
            files = ['<script type="text/javascript" src="/{0}"></script>\n'.format(f) for f in files]
        elif extension == 'css':
            files = ['<link rel="stylesheet" rel="{0}" href="{1}" />\n'.format(rel, f) for f in files]
        return Markup(''.join(files))

    files = [
        (f, 'static/{0}'.format(f))
        for f in files
    ]

    # Build a key based off the files in question
    outfile = ''.join(chain.from_iterable((f[0], f[1]) for f in files))
    outfile = md5(outfile).hexdigest()

    bundle = None
    # Does the bundle already exist?
    if outfile not in assets:
        bundle = Bundle(*[f[1] for f in files],
            output='static/cache/{0}.{1}'.format(outfile, extension),
            filters=filters
        )
        assets.register(outfile, bundle)

    if extension == 'js':
        outfile = '<script type="text/javascript" src="/inc/cache/{0}.{1}"></script>'.format(outfile, extension)
    elif extension == 'css':
        outfile = '<link rel="stylesheet" rel="{0}" href="{1}" />'.format(rel, extension)

    return Markup(outfile)

app.jinja_env.globals['assets'] = bundle_assets