The decorator 'foo' works fine in flask 0.9, but it does not work in 0.10.1. http://flask.pocoo.org/snippets/18/ is also same result.

gistfile1.pytb

Traceback (most recent call last):
  File "./hello.py", line 31, in <module>
    def hello(name=None):
  File "./hello.py", line 15, in deco
    @wraps(f)
  File "/Users/mckabi/Documents/Sandbox/flask_ex/env/lib/python2.7/site-packages/flask/app.py", line 1013, in decorator
    self.add_url_rule(rule, endpoint, f, **options)
  File "/Users/mckabi/Documents/Sandbox/flask_ex/env/lib/python2.7/site-packages/flask/app.py", line 62, in wrapper_func
    return f(self, *args, **kwargs)
  File "/Users/mckabi/Documents/Sandbox/flask_ex/env/lib/python2.7/site-packages/flask/app.py", line 984, in add_url_rule
    'existing endpoint function: %s' % endpoint)
AssertionError: View function mapping is overwriting an existing endpoint function: hello

hello.py

def foo(current_app, url, postfix='blah blah', *args, **kwargs):
    def deco(f):
    	@current_app.route(url, defaults=kwargs.pop('defaults', {}), *args, **kwargs)
		@wraps(f)
		def decorated_func(*args, **kwargs):
			sys.stdout.write('... in decorated_func, foo({0!r}) with {1!r}\n'.format(f, postfix))
			sys.stdout.flush()
			return f(*args, **kwargs)
		decorated_func._orig = f
		return decorated_func
	return deco


@foo(app, '/hello', 'first foo')
@foo(app, '/hello/<name>', 'second foo')
def hello(name=None):
	return {'name': name}

My solution is:

def bind_renderer(renderer=None):
    def wrapper(f):
        @wraps(f)
        def decorated_function(*args, **kwargs):
            result = f(*args, **kwargs)
            if isinstance(result, (Response, BaseResponse)):
                return result
            if renderer is None or not callable(renderer):
                return result
            try:
                return renderer()(result)
            except TypeError:
                return renderer(result)
        return decorated_function
    return wrapper


@app.route('/hello')
@app.route('/hello/<name>')
@bind_renderer(render_json)
def hello(name=None):
    return {'name': name}

I think this solution is close to the flask style.