Add JSONIFY_END_WITH_NEWLINE config variable

When `JSONIFY_END_WITH_NEWLINE` is set to `True`, `jsonify`
responses will be terminated with a newline character.

Defaults to `False` for backward compatibility.

This came up in the context of
https://github.com/kennethreitz/httpbin/issues/168

CHANGES

@@ -53,6 +53,7 @@ Version 1.0
 - Add "pretty" and "compressed" separators definitions in jsonify() method.
   Reduces JSON response size when JSONIFY_PRETTYPRINT_REGULAR=False by removing
   unnecessary white space included by default after separators.
+- Added the ``JSONIFY_END_WITH_NEWLINE`` configuration variable.
 
 
 Version 0.10.2

docs/config.rst

@@ -182,6 +182,9 @@ The following configuration values are used internally by Flask:
                                   if they are not requested by an
                                   XMLHttpRequest object (controlled by
                                   the ``X-Requested-With`` header)
+``JSONIFY_END_WITH_NEWLINE``      If this is set to ``True``, ``jsonify``
+                                  responses will be terminated with a newline
+                                  character.
 ``TEMPLATES_AUTO_RELOAD``         Whether to check for modifications of
                                   the template source and reload it
                                   automatically. By default the value is

flask/app.py

@@ -297,6 +297,7 @@ def _set_request_globals_class(self, value):
         'JSON_AS_ASCII':                        True,
         'JSON_SORT_KEYS':                       True,
         'JSONIFY_PRETTYPRINT_REGULAR':          True,
+        'JSONIFY_END_WITH_NEWLINE':             False,
         'TEMPLATES_AUTO_RELOAD':                None,
     })
 

flask/json.py

@@ -200,8 +200,9 @@ def htmlsafe_dump(obj, fp, **kwargs):
 
 def jsonify(*args, **kwargs):
     """Creates a :class:`~flask.Response` with the JSON representation of
-    the given arguments with an :mimetype:`application/json` mimetype.  The arguments
-    to this function are the same as to the :class:`dict` constructor.
+    the given arguments with an :mimetype:`application/json` mimetype.  The
+    arguments to this function are the same as to the :class:`dict`
+    constructor.
 
     Example usage::
 
@@ -231,6 +232,9 @@ def get_current_user():
     spaces after separators.
 
     .. versionadded:: 0.2
+
+    To ensure that the output is terminated with a newline, set the
+    ``JSONIFY_END_WITH_NEWLINE`` config parameter.
     """
 
     indent = None
@@ -241,9 +245,13 @@ def get_current_user():
         indent = 2
         separators = (', ', ': ')
 
-    return current_app.response_class(dumps(dict(*args, **kwargs),
-        indent=indent, separators=separators),
+    rv = current_app.response_class(
+        dumps(dict(*args, **kwargs), indent=indent, separators=separators),
         mimetype='application/json')
+    if current_app.config['JSONIFY_END_WITH_NEWLINE']:
+        if not rv.data.endswith(b'\n'):
+            rv.data += b'\n'
+    return rv
 
 
 def tojson_filter(obj, **kwargs):

tests/test_basic.py

@@ -989,6 +989,19 @@ def test_jsonify_prettyprint():
         assert rv.data == pretty_response
 
 
+def test_jsonify_end_with_newline():
+    app = flask.Flask(__name__)
+    app.config.update({"JSONIFY_END_WITH_NEWLINE": True})
+    with app.test_request_context():
+        compressed_msg = {"msg":{"submsg":"W00t"},"msg2":"foobar"}
+        pretty_response =\
+            b'{\n  "msg": {\n    "submsg": "W00t"\n  }, \n  "msg2": "foobar"\n}\n'
+
+        rv = flask.make_response(
+            flask.jsonify(compressed_msg), 200)
+        assert rv.data == pretty_response
+
+
 def test_url_generation():
     app = flask.Flask(__name__)