LiveReload compatibility hack for Webassets

readme.txt

Tested with LiveReload 2.3.18

The only requirement is that the updating requests are sent with ?livereload={etc} in the url.
LiveReload should be configured to NOT compile the assets, as we want webassets to take care of this. We're
just using LR for the notification/loading parts.

webassets_livereload.py

import re
import os
from flask import current_app, redirect

def get_bundle_from_output(path, env_or_bundles):
    for bundle in env_or_bundles:
        output = getattr(bundle, 'output', None)
        if output == path:
            return bundle
        elif output and '%(version)s' in output:
            pattern = re.escape(output).replace('\%\(version\)s', '(\\w+)')
            if re.match(pattern, path):
                return bundle

        if hasattr(bundle, 'contents'):
            children = get_bundle_from_output(path, bundle.contents)
            if children:
                return children


# Example Flask handler

@app.before_request
def livereload():
    if 'livereload' in request.args:
        path = os.path.relpath(request.path, assets_env.url)
        bundle = get_bundle_from_output(path, assets_env)
        if bundle:
            print 'Building', bundle
            bundle.build(env=assets_env)
            url = bundle.urls(env=assets_env)[0]
            if url.split('?')[0] != request.path:
                print 'Url changed, redirecting to', url
                return redirect(url)
        else:
            print 'No bundle found for', path