>Need to access the request? use `req`

Well, I don't see what's especially difficult about this?

    from flask import request

    @app.route('/login', methods=['GET', 'POST'])
    def login():
        if request.method == 'POST':
            return do_the_login()
        else:
            return show_the_login_form()

I would actually argue that this is better, since I have to type "request" only once.

Although I have to admitt, the middleware thing looks quite composable.