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adding `_scheme` parameter to `url_for`

In order to better facilitate generation of URLs that make use of an HTTPS URL
scheme this patch adds a parameter with this specific purpose in mind. To
achieve this we explicitly pass in a param, `_scheme='https'`, and then set the
`url_scheme` attribute of our `MapAdapter` instance appropriately.

Importantly, `_external=True` must be set in order for this to work properly.
As such, failure to do so results in a `ValueError` being raised.
commit b5069d07a24a3c3a54fb056aa6f4076a0e7088c7 1 parent 61d3bbf
@maxcountryman maxcountryman authored
Showing with 34 additions and 0 deletions.
  1. +12 −0 flask/
  2. +22 −0 flask/testsuite/
12 flask/
@@ -229,6 +229,9 @@ def external_url_handler(error, endpoint, **values):
that this is for building URLs outside the current application, and not for
handling 404 NotFound errors.
+ .. versionadded:: 0.10
+ The `_scheme` parameter was added.
.. versionadded:: 0.9
The `_anchor` and `_method` parameters were added.
@@ -241,6 +244,8 @@ def external_url_handler(error, endpoint, **values):
:param _external: if set to `True`, an absolute URL is generated. Server
address can be changed via `SERVER_NAME` configuration variable which
defaults to `localhost`.
+ :param _scheme: a string specifying the desired URL scheme. The `_external`
+ parameter must be set to `True` or a `ValueError` is raised.
:param _anchor: if provided this is added as anchor to the URL.
:param _method: if provided this explicitly specifies an HTTP method.
@@ -283,7 +288,14 @@ def external_url_handler(error, endpoint, **values):
anchor = values.pop('_anchor', None)
method = values.pop('_method', None)
+ scheme = values.pop('_scheme', None), values)
+ if scheme is not None:
+ if not external:
+ raise ValueError('When specifying _scheme, _external must be True')
+ url_adapter.url_scheme = scheme
rv =, values, method=method,
22 flask/testsuite/
@@ -397,6 +397,28 @@ def index():
self.assert_equal(flask.url_for('index', _anchor='x y'),
+ def test_url_for_with_scheme(self):
+ app = flask.Flask(__name__)
+ @app.route('/')
+ def index():
+ return '42'
+ with app.test_request_context():
+ self.assert_equal(flask.url_for('index',
+ _external=True,
+ _scheme='https'),
+ 'https://localhost/')
+ def test_url_for_with_scheme_not_external(self):
+ app = flask.Flask(__name__)
+ @app.route('/')
+ def index():
+ return '42'
+ with app.test_request_context():
+ self.assert_raises(ValueError,
+ flask.url_for,
+ 'index',
+ _scheme='https')
def test_url_with_method(self):
from flask.views import MethodView
app = flask.Flask(__name__)
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