Add ability to config from a JSON file

flask/config.py

@@ -15,6 +15,7 @@ import errno
 
 from werkzeug.utils import import_string
 from ._compat import string_types
+from . import json
 
 
 class ConfigAttribute(object):
@@ -164,5 +165,31 @@ class Config(dict):
             if key.isupper():
                 self[key] = getattr(obj, key)
 
+    def from_json(self, filename, silent=False):
+        """Updates the values in the config from a JSON file. This function
+        behaves as if the JSON object was a dictionary and passed ot the
+        :meth:`from_object` function.
+
+        :param filename: the filename of the JSON file.  This can either be an
+                         absolute filename or a filename relative to the
+                         root path.
+        :param silent: set to `True` if you want silent failure for missing
+                       files.
+        """
+        filename = os.path.join(self.root_path, filename)
+
+        try:
+            with open(filename) as json_file:
+                obj = json.loads(json_file.read())
+        except IOError as e:
+            if silent and e.errno in (errno.ENOENT, errno.EISDIR):
+                return False
+            e.strerror = 'Unable to load configuration file (%s)' % e.strerror
+            raise
+        for key in obj.keys():
+            if key.isupper():
+                self[key] = obj[key]
+        return True
+
     def __repr__(self):
         return '<%s %s>' % (self.__class__.__name__, dict.__repr__(self))

flask/testsuite/config.py

@@ -40,6 +40,12 @@ class ConfigTestCase(FlaskTestCase):
         app.config.from_object(__name__)
         self.common_object_test(app)
 
+    def test_config_from_json(self):
+        app = flask.Flask(__name__)
+        current_dir = os.path.dirname(os.path.abspath(__file__))
+        app.config.from_json(os.path.join(current_dir, 'static', 'config.json'))
+        self.common_object_test(app)
+
     def test_config_from_class(self):
         class Base(object):
             TEST_KEY = 'foo'
@@ -99,6 +105,19 @@ class ConfigTestCase(FlaskTestCase):
             self.assert_true(0, 'expected config')
         self.assert_false(app.config.from_pyfile('missing.cfg', silent=True))
 
+    def test_config_missing_json(self):
+        app = flask.Flask(__name__)
+        try:
+            app.config.from_json('missing.json')
+        except IOError as e:
+            msg = str(e)
+            self.assert_true(msg.startswith('[Errno 2] Unable to load configuration '
+                                            'file (No such file or directory):'))
+            self.assert_true(msg.endswith("missing.json'"))
+        else:
+            self.assert_true(0, 'expected config')
+        self.assert_false(app.config.from_json('missing.json', silent=True))
+
     def test_session_lifetime(self):
         app = flask.Flask(__name__)
         app.config['PERMANENT_SESSION_LIFETIME'] = 42

flask/testsuite/static/config.json

@@ -0,0 +1,4 @@
+{
+    "TEST_KEY": "foo",
+    "SECRET_KEY": "devkey"
+}