Changed the implementation of returning tuples from functions

CHANGES

@@ -63,6 +63,8 @@ Relase date to be decided, codename to be chosen.
   the `get_send_file_options` hook is used.
 - Fixed an assumption in sessions implementation which could break message
   flashing on sessions implementations which use external storage.
+- Changed the behavior of tuple return values from functions.  They are no
+  longer arguments to the response object, they now have a defined meaning.
 
 Version 0.8.1
 -------------

docs/quickstart.rst

@@ -674,8 +674,11 @@ converting return values into response objects is as follows:
     returned from the view.
 2.  If it's a string, a response object is created with that data and the
     default parameters.
-3.  If a tuple is returned the response object is created by passing the
-    tuple as arguments to the response object's constructor.
+3.  If a tuple is returned the items in the tuple can provide extra
+    information.  Such tuples have to be in the form ``(response, status,
+    headers)`` where at least one item has to be in the tuple.  The
+    `status` value will override the status code and `headers` can be a
+    list or dictionary of additional header values.
 4.  If none of that works, Flask will assume the return value is a
     valid WSGI application and convert that into a response object.
 

docs/upgrading.rst

@@ -19,6 +19,21 @@ installation, make sure to pass it the ``-U`` parameter::
 
     $ easy_install -U Flask
 
+Version 0.9
+-----------
+
+The behavior of returning tuples from a function was simplified.  If you
+return a tuple it no longer defines the arguments for the response object
+you're creating, it's now always a tuple in the form ``(response, status,
+headers)`` where at least one item has to be provided.  If you depend on
+the old behavior, you can add it easily by subclassing Flask::
+
+    class TraditionalFlask(Flask):
+        def make_response(self, rv):
+            if isinstance(rv, tuple):
+                return self.response_class(*rv)
+            return Flask.make_response(self, rv)
+
 Version 0.8
 -----------
 

flask/app.py

@@ -1354,37 +1354,48 @@ class Flask(_PackageBoundObject):
                                 string as body
         :class:`unicode`        a response object is created with the
                                 string encoded to utf-8 as body
-        :class:`tuple`          the response object is created with the
-                                contents of the tuple as arguments
         a WSGI function         the function is called as WSGI application
                                 and buffered as response object
+        :class:`tuple`          A tuple in the form ``(response, status,
+                                headers)`` where `response` is any of the
+                                types defined here, `status` is a string
+                                or an integer and `headers` is a list of
+                                a dictionary with header values.
         ======================= ===========================================
 
         :param rv: the return value from the view function
+
+        .. versionchanged:: 0.9
+           Previously a tuple was interpreted as the arguments for the
+           response object.
         """
+        status = headers = None
+        if isinstance(rv, tuple):
+            rv, status, headers = rv + (None,) * (3 - len(rv))
+
         if rv is None:
             raise ValueError('View function did not return a response')
-        if isinstance(rv, self.response_class):
-            return rv
-        if isinstance(rv, basestring):
-            return self.response_class(rv)
-        if isinstance(rv, tuple):
-            if len(rv) > 0 and isinstance(rv[0], self.response_class):
-                original = rv[0]
-                new_response = self.response_class('', *rv[1:])
-                if len(rv) < 3:
-                    # The args for the response class are
-                    # response=None, status=None, headers=None,
-                    # mimetype=None, content_type=None, ...
-                    # so if there's at least 3 elements the rv
-                    # tuple contains header information so the
-                    # headers from rv[0] "win."
-                    new_response.headers = original.headers
-                new_response.response = original.response
-                return new_response
+
+        if not isinstance(rv, self.response_class):
+            # When we create a response object directly, we let the constructor
+            # set the headers and status.  We do this because there can be
+            # some extra logic involved when creating these objects with
+            # specific values (like defualt content type selection).
+            if isinstance(rv, basestring):
+                rv = self.response_class(rv, headers=headers, status=status)
+                headers = status = None
             else:
-                return self.response_class(*rv)
-        return self.response_class.force_type(rv, request.environ)
+                rv = self.response_class.force_type(rv, request.environ)
+
+        if status is not None:
+            if isinstance(status, basestring):
+                rv.status = status
+            else:
+                rv.status_code = status
+        if headers:
+            rv.headers.extend(headers)
+
+        return rv
 
     def create_url_adapter(self, request):
         """Creates a URL adapter for the given request.  The URL adapter

flask/testsuite/basic.py

@@ -631,7 +631,10 @@ class BasicFunctionalityTestCase(FlaskTestCase):
             return u'Hällo Wörld'.encode('utf-8')
         @app.route('/args')
         def from_tuple():
-            return 'Meh', 400, {'X-Foo': 'Testing'}, 'text/plain'
+            return 'Meh', 400, {
+                'X-Foo': 'Testing',
+                'Content-Type': 'text/plain; charset=utf-8'
+            }
         c = app.test_client()
         self.assert_equal(c.get('/unicode').data, u'Hällo Wörld'.encode('utf-8'))
         self.assert_equal(c.get('/string').data, u'Hällo Wörld'.encode('utf-8'))
@@ -677,16 +680,10 @@ class BasicFunctionalityTestCase(FlaskTestCase):
 
             rv = flask.make_response(
                 flask.Response('', headers={'Content-Type': 'text/html'}),
-                400, None, 'application/json')
-            self.assertEqual(rv.status_code, 400)
-            self.assertEqual(rv.headers['Content-Type'], 'application/json')
-
-            rv = flask.make_response(
-                flask.Response('', mimetype='application/json'),
-                400, {'Content-Type': 'text/html'})
+                400, [('X-Foo', 'bar')])
             self.assertEqual(rv.status_code, 400)
             self.assertEqual(rv.headers['Content-Type'], 'text/html')
-
+            self.assertEqual(rv.headers['X-Foo'], 'bar')
 
     def test_url_generation(self):
         app = flask.Flask(__name__)