Unable to use Babel Filter with Jinja Extension

[deckar01]

I setup the Jinja extension and it works great. When I add "babel" to the filters argument, babel does not appear to be processing the assets. I believe Babel requires a preset to be provided otherwise it passes the code through untouched.

I do not see a way to provide the es2015 preset to babel using the Jinja asset tag.

{% assets filters='babel', output=output, filepath %}
  <script type="text/javascript" src="{{ ASSET_URL }}"></script>
{% endassets %}

The docs for the babel filter only show it being used with the bundle interface:

Example python bundle:

es2015 = get_filter('babel', presets='es2015')
bundle = Bundle('**/*.js', filters=es2015)

builtin_filters.html#webassets.filter.babel.Babel

[deckar01]

I also tried setting the OS environment variable for BABEL_PRESETS to es2015, but it did not seem to make a difference.

[deckar01]

Ok, I was able to get this working. The underlying issue was that the babel presets don't invalidate the cache... I though I had cleared the cache by wiping the .webassets-cache directory, but apparently I had to wipe my output directory also.

For future reference, the cleanest way to configure filters is using the asset config:

assets_environment = AssetsEnvironment(...)
assets_environment.config['BABEL_PRESETS'] = 'es2015'

@miracle2k I didn't find this info until I read the options section of Creating custom filters. Would you be interested in reviewing a PR that adds this to the Using the tag section of the Jinja2 docs? Is there any other place in the docs that you think this information would be useful?