It resolves problems with blueprints and url_prefix "/"

[guilleJB]

Issue #348

I want to separate an app with various blueprints, frontend, backend, etc.. But when I try to register my frontend blueprint with follow code, my static css, images, js don't load.

front = Blueprint('front', __name__, static_folder='static', template_folder='./templates', url_prefix='/')

After debugging I found the problem. It's when try to register route, it tries to register route like //static (https://github.com/mitsuhiko/flask/blob/master/flask/blueprints.py#L68)

And then when use url_for the werkzeug routing.py (https://github.com/mitsuhiko/werkzeug/blob/master/werkzeug/routing.py#L1655) resolve url_for //static/filename it found a problem beacause there are two rules like this:

[<Rule '/static/<filename>' (HEAD, OPTIONS, GET) -> static>, <Rule '//static/<filename>' (HEAD, OPTIONS, GET) -> front.static>]

So, a simple solution like concatenate a blueprint.name before url_prefix when is "/" resolve this conflict and now we can use url_for('front.static', filename='2.jpg') routing resolves without problem.

[untitaker]

Hello @guilleJB, thanks for your contribution! Sorry for making you wait so long, but I don't believe this is a correct fix. It special-cases a particular setting of yours, but I'm sure there's a bug somewhere else.