RuntimeError: Assets Instance Not Bound To An Application, And No Application In Current Context

I'm working to modify a cookiecutter Flask app. I'm currently trying to add a datepicker to a page. I've found https://eonasdan.github.io/bootstrap-datetimepicker/. This cookiecut

Solution 1:

As I noted in my comment, you have to a Flask app bound to the object, as it notes in the traceback:

>>> RuntimeError: assets instance not bound to an application, and no 
    application in current context

This will fix your problem, whether or not it's relevant for you use case...:

def register_extensions(app):
    assets.init_app(app)
    with app.app_context():
         assets.load_path = ['static']

or you could re-write your create app to have

def create_assets(app):
    assets = Environment(app)
    ....
    assets.load_path ['static']
    return assets

def create_app():
    app = Flask()
    ....
    assets = create_assets(app)
    return app

The whole reason for your errors is your call to load_path. This tries to set the attribute in webassets, which you can see here: https://github.com/miracle2k/webassets/blob/95dff0ad6dcc25b81790a1585c67f5393e7d32af/src/webassets/env.py#L656

def _set_load_path(self, load_path):
    self._storage['load_path'] = load_path

In turn, this now activates the attribute of _storage on your flask-asset object, which results in it trying to do this: https://github.com/miracle2k/flask-assets/blob/eb7f1905410828689086b80eb19be9331041ac52/src/flask_assets.py#L102

def __setitem__(self, key, value):
    if not self._set_deprecated(key, value):
        self.env._app.config[self._transform_key(key)] = value

As you see, it needs access to an app, and as you haven't given one when you used load_path it will complain to you, as it explains so nicely in the Traceback. I found a discussion about this on the flask-asset page: https://github.com/miracle2k/flask-assets/issues/35

You may, quite rightly, think that as you called init_app() that everything should be fine, but that's not the case, init_app() does not give any reference of the app to Environment: https://github.com/miracle2k/flask-assets/blob/eb7f1905410828689086b80eb19be9331041ac52/src/flask_assets.py#L338

def init_app(self, app):
    app.jinja_env.add_extension('webassets.ext.jinja2.AssetsExtension')
    app.jinja_env.assets_environment = self

I don't use flask-assets at all, and so I'm not particularly sure why they haven't referenced the app with the Environment().init_app, so if someone else knows, shout out.