From 90a50f8b51bdd71d9f2b1fd82352628cfd681898 Mon Sep 17 00:00:00 2001
From: Matt Wright <matt@nobien.net>
Date: Thu, 23 Jan 2014 15:05:37 -0500
Subject: [PATCH] Add `get_namespace` method on `Config` object for convenient
 access of namespaced config options.

---
 flask/config.py           | 34 ++++++++++++++++++++++++++++++++++
 flask/testsuite/config.py | 15 +++++++++++++++
 2 files changed, 49 insertions(+)

diff --git a/flask/config.py b/flask/config.py
index 07d6fbc8..66bf7eb4 100644
--- a/flask/config.py
+++ b/flask/config.py
@@ -164,5 +164,39 @@ class Config(dict):
             if key.isupper():
                 self[key] = getattr(obj, key)
 
+    def get_namespace(self, namespace, lowercase=True):
+        """Returns a dictionary containing a subset of configuration options
+        that match the specified namespace/prefix. Example usage::
+
+            app.config['IMAGE_STORE_TYPE'] = 'fs'
+            app.config['IMAGE_STORE_PATH'] = '/var/app/images'
+            app.config['IMAGE_STORE_BASE_URL'] = 'http://img.website.com'
+            image_store_config = app.config.get_namespace('IMAGE_STORE_')
+
+        The resulting dictionary `image_store` would look like::
+
+            {
+                'type': 'fs',
+                'path': '/var/app/images',
+                'base_url': 'http://img.website.com'
+            }
+
+        This is often useful when configuration options map directly to
+        keyword arguments in functions or class constructors.
+
+        :param namespace: a configuration namespace
+        :param lowercase: a flag indicating if the keys of the resulting
+                          dictionary should be lowercase
+        """
+        rv = {}
+        for k, v in self.iteritems():
+            if not k.startswith(namespace):
+                continue
+            key = k[len(namespace):]
+            if lowercase:
+                key = key.lower()
+            rv[key] = v
+        return rv
+
     def __repr__(self):
         return '<%s %s>' % (self.__class__.__name__, dict.__repr__(self))
diff --git a/flask/testsuite/config.py b/flask/testsuite/config.py
index cdc6273f..c2c14cb1 100644
--- a/flask/testsuite/config.py
+++ b/flask/testsuite/config.py
@@ -105,6 +105,21 @@ class ConfigTestCase(FlaskTestCase):
         app.config['PERMANENT_SESSION_LIFETIME'] = 42
         self.assert_equal(app.permanent_session_lifetime.seconds, 42)
 
+    def test_get_namespace(self):
+        app = flask.Flask(__name__)
+        app.config['FOO_OPTION_1'] = 'foo option 1'
+        app.config['FOO_OPTION_2'] = 'foo option 2'
+        app.config['BAR_STUFF_1'] = 'bar stuff 1'
+        app.config['BAR_STUFF_2'] = 'bar stuff 2'
+        foo_options = app.config.get_namespace('FOO_')
+        self.assert_equal(2, len(foo_options))
+        self.assert_equal('foo option 1', foo_options['option_1'])
+        self.assert_equal('foo option 2', foo_options['option_2'])
+        bar_options = app.config.get_namespace('BAR_', lowercase=False)
+        self.assert_equal(2, len(bar_options))
+        self.assert_equal('bar stuff 1', bar_options['STUFF_1'])
+        self.assert_equal('bar stuff 2', bar_options['STUFF_2'])
+
 
 class LimitedLoaderMockWrapper(object):
     def __init__(self, loader):