Added support for unicode json dumping. This fixes #535

CHANGES

@@ -30,6 +30,10 @@ Release date to be decided.
 - The config object is now available to the template as a real global and
   not through a context processor which makes it available even in imported
   templates by default.
+- Added an option to generate non-ascii encoded JSON which should result
+  in less bytes being transmitted over the network.  It's disabled by
+  default to not cause confusion with existing libraries that might expect
+  ``flask.json.dumps`` to return bytestrings by default.
 
 Version 0.9
 -----------

docs/config.rst

@@ -142,6 +142,13 @@ The following configuration values are used internally by Flask:
 ``PREFERRED_URL_SCHEME``          The URL scheme that should be used for
                                   URL generation if no URL scheme is
                                   available.  This defaults to ``http``.
+``JSON_AS_ASCII``                 By default Flask serialize object to
+                                  ascii-encoded JSON.  If this is set to
+                                  ``False`` Flask will not encode to ASCII
+                                  and output strings as-is and return
+                                  unicode strings.  ``jsonfiy`` will
+                                  automatically encode it in ``utf-8``
+                                  then for transport for instance.
 ================================= =========================================
 
 .. admonition:: More on ``SERVER_NAME``
@@ -184,6 +191,9 @@ The following configuration values are used internally by Flask:
 .. versionadded:: 0.9
    ``PREFERRED_URL_SCHEME``
 
+.. versionadded:: 0.10
+   ``JSON_AS_ASCII``
+
 Configuring from Files
 ----------------------
 

flask/app.py

@@ -274,7 +274,8 @@ class Flask(_PackageBoundObject):
         'SEND_FILE_MAX_AGE_DEFAULT':            12 * 60 * 60, # 12 hours
         'TRAP_BAD_REQUEST_ERRORS':              False,
         'TRAP_HTTP_EXCEPTIONS':                 False,
-        'PREFERRED_URL_SCHEME':                 'http'
+        'PREFERRED_URL_SCHEME':                 'http',
+        'JSON_AS_ASCII':                        True
     })
 
     #: The rule object to use for URL rules created.  This is used by

flask/json.py

@@ -68,20 +68,37 @@ class JSONDecoder(_json.JSONDecoder):
     """
 
 
+def _dump_arg_defaults(kwargs):
+    """Inject default arguments for dump functions."""
+    if current_app:
+        kwargs.setdefault('cls', current_app.json_encoder)
+        if not current_app.config['JSON_AS_ASCII']:
+            kwargs.setdefault('ensure_ascii', False)
+
+
+def _load_arg_defaults(kwargs):
+    """Inject default arguments for load functions."""
+    if current_app:
+        kwargs.setdefault('cls', current_app.json_decoder)
+
+
 def dumps(obj, **kwargs):
     """Serialize ``obj`` to a JSON formatted ``str`` by using the application's
     configured encoder (:attr:`~flask.Flask.json_encoder`) if there is an
     application on the stack.
+
+    This function can return ``unicode`` strings or ascii-only bytestrings by
+    default which coerce into unicode strings automatically.  That behavior by
+    default is controlled by the ``JSON_AS_ASCII`` configuration variable
+    and can be overriden by the simplejson ``ensure_ascii`` parameter.
     """
-    if current_app:
-        kwargs.setdefault('cls', current_app.json_encoder)
+    _dump_arg_defaults(kwargs)
     return _json.dumps(obj, **kwargs)
 
 
 def dump(obj, fp, **kwargs):
     """Like :func:`dumps` but writes into a file object."""
-    if current_app:
-        kwargs.setdefault('cls', current_app.json_encoder)
+    _dump_arg_defaults(kwargs)
     return _json.dump(obj, fp, **kwargs)
 
 
@@ -90,16 +107,14 @@ def loads(s, **kwargs):
     configured decoder (:attr:`~flask.Flask.json_decoder`) if there is an
     application on the stack.
     """
-    if current_app:
-        kwargs.setdefault('cls', current_app.json_decoder)
+    _load_arg_defaults(kwargs)
     return _json.loads(s, **kwargs)
 
 
 def load(fp, **kwargs):
     """Like :func:`loads` but reads from a file object.
     """
-    if current_app:
-        kwargs.setdefault('cls', current_app.json_decoder)
+    _load_arg_defaults(kwargs)
     return _json.load(fp, **kwargs)
 
 

flask/testsuite/helpers.py

@@ -79,6 +79,19 @@ class JSONTestCase(FlaskTestCase):
             self.assert_equal(rv.mimetype, 'application/json')
             self.assert_equal(flask.json.loads(rv.data), d)
 
+    def test_json_as_unicode(self):
+        app = flask.Flask(__name__)
+
+        app.config['JSON_AS_ASCII'] = True
+        with app.app_context():
+            rv = flask.json.dumps(u'\N{SNOWMAN}')
+            self.assert_equal(rv, '"\\u2603"')
+
+        app.config['JSON_AS_ASCII'] = False
+        with app.app_context():
+            rv = flask.json.dumps(u'\N{SNOWMAN}')
+            self.assert_equal(rv, u'"\u2603"')
+
     def test_json_attr(self):
         app = flask.Flask(__name__)
         @app.route('/add', methods=['POST'])