Issue with Flask 0.10.1 documentation as written.

as_working.py

# -*- coding: utf-8 -*-

import sys
from flask import Flask, url_for


app = Flask(__name__)


@app.route("/")
def index():
    return url_for('take_me_to_flask', ignore_me="okay"),


def lookup_url(endpoint, **values):
    '''Mock method for docs example to load.'''
    if endpoint == 'take_me_to_flask':
        return 'http://flask.pocoo.org/'
    else:
        return None


def external_url_handler(error, endpoint, values):
    print values
    url = lookup_url(endpoint, **values)
    if url is None:
        # External lookup did not have a URL.
        # Re-raise the BuildError, in context of original traceback.
        exc_type, exc_value, tb = sys.exc_info()
        if exc_value is error:
            raise exc_type, exc_value, tb
        else:
            raise error
    # url_for will use this result, instead of raising BuildError.
    return url

app.url_build_error_handlers.append(external_url_handler)

if __name__ == '__main__':
    app.run(debug=True)

per_documentation.py

# -*- coding: utf-8 -*-

import sys
from flask import Flask, url_for


app = Flask(__name__)


@app.route('/')
def index():
    return url_for('take_me_to_flask', ignore_me="okay")


def lookup_url(endpoint, **values):
    '''Mock method for docs example to load.'''
    if endpoint == 'take_me_to_flask':
        return 'http://flask.pocoo.org/'
    else:
        return None


##################################
## Start code copied from API docs

def external_url_handler(error, endpoint, **values):
    "Looks up an external URL when `url_for` cannot build a URL."
    # This is an example of hooking the build_error_handler.
    # Here, lookup_url is some utility function you've built
    # which looks up the endpoint in some external URL registry.
    url = lookup_url(endpoint, **values)
    if url is None:
        # External lookup did not have a URL.
        # Re-raise the BuildError, in context of original traceback.
        exc_type, exc_value, tb = sys.exc_info()
        if exc_value is error:
            raise exc_type, exc_value, tb
        else:
            raise error
    # url_for will use this result, instead of raising BuildError.
    return url

app.build_error_handler = external_url_handler

##################################
## End code copied from API docs

if __name__ == '__main__':
    app.run(debug=True)

per_documentation.traceback

127.0.0.1 - - [11/Oct/2013 16:23:38] "GET / HTTP/1.1" 500 -
Traceback (most recent call last):
  File "/home/jmhobbs/Desktop/example/venv/lib/python2.7/site-packages/flask/app.py", line 1836, in __call__
    return self.wsgi_app(environ, start_response)
  File "/home/jmhobbs/Desktop/example/venv/lib/python2.7/site-packages/flask/app.py", line 1820, in wsgi_app
    response = self.make_response(self.handle_exception(e))
  File "/home/jmhobbs/Desktop/example/venv/lib/python2.7/site-packages/flask/app.py", line 1403, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "/home/jmhobbs/Desktop/example/venv/lib/python2.7/site-packages/flask/app.py", line 1817, in wsgi_app
    response = self.full_dispatch_request()
  File "/home/jmhobbs/Desktop/example/venv/lib/python2.7/site-packages/flask/app.py", line 1477, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/home/jmhobbs/Desktop/example/venv/lib/python2.7/site-packages/flask/app.py", line 1381, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/home/jmhobbs/Desktop/example/venv/lib/python2.7/site-packages/flask/app.py", line 1475, in full_dispatch_request
    rv = self.dispatch_request()
  File "/home/jmhobbs/Desktop/example/venv/lib/python2.7/site-packages/flask/app.py", line 1461, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/home/jmhobbs/Desktop/example/per_documentation.py", line 12, in index
    return url_for('take_me_to_flask', ignore_me="okay")
  File "/home/jmhobbs/Desktop/example/venv/lib/python2.7/site-packages/flask/helpers.py", line 312, in url_for
    return appctx.app.handle_url_build_error(error, endpoint, values)
  File "/home/jmhobbs/Desktop/example/venv/lib/python2.7/site-packages/flask/app.py", line 1641, in handle_url_build_error
    reraise(exc_type, exc_value, tb)
  File "/home/jmhobbs/Desktop/example/venv/lib/python2.7/site-packages/flask/helpers.py", line 305, in url_for
    force_external=external)
  File "/home/jmhobbs/Desktop/example/venv/lib/python2.7/site-packages/werkzeug/routing.py", line 1620, in build
    raise BuildError(endpoint, values, method)
BuildError: ('take_me_to_flask', {'ignore_me': 'okay'}, None)

requirements.txt

Flask==0.10.1
Jinja2==2.7.1
MarkupSafe==0.18
Werkzeug==0.9.4
argparse==1.2.1
distribute==0.6.24
itsdangerous==0.23
wsgiref==0.1.2