content: Add install and get_settings functions.

README.rst

@@ -12,6 +12,25 @@ This mix-in adds two methods to a ``tornado.web.RequestHandler`` instance:
 - ``send_response(object)``: serializes the response into the content type
   requested by the ``Accept`` header.
 
+Before adding support for specific content types, you SHOULD install the
+content settings into your ``tornado.web.Application`` instance.  If you
+don't install the content settings, then an instance will be created for
+you by the mix-in; however, the created instance will be empty.  You
+should already have a function that creates the ``Application`` instance.
+If you don't, now is a good time to add one.
+
+.. code-block:: python
+
+   from sprockets.mixins.mediatype import content
+   from tornado import web
+
+   def make_application():
+       application = web.Application([
+           # insert your handlers here
+       ])
+       content.install(application, 'application/json', 'utf-8')
+       return application
+
 Support for a content types is enabled by calling ``add_binary_content_type``,
 ``add_text_content_type`` or the ``add_transcoder`` functions with the
 ``tornado.web.Application`` instance, the content type, encoding and decoding
@@ -29,6 +48,7 @@ functions as parameters:
            # insert your handlers here
        ])
 
+       content.install(application, 'application/json', 'utf-8')
        content.add_text_content_type(application,
                                      'application/json', 'utf-8',
                                      json.dumps, json.loads)
@@ -52,6 +72,7 @@ types:
            # insert your handlers here
        ])
 
+       content.install(application, 'application/json', 'utf-8')
        content.add_transcoder(application, transcoders.JSONTranscoder())
 
        return application

docs/api.rst

@@ -9,6 +9,10 @@ Content Type Handling
 
 Content Type Registration
 -------------------------
+.. autofunction:: install
+
+.. autofunction:: get_settings
+
 .. autofunction:: set_default_content_type
 
 .. autofunction:: add_binary_content_type

docs/history.rst

@@ -1,5 +1,9 @@
 Version History
 ===============
+`Next Release`_
+---------------
+- Add :func:`sprockets.mixins.mediatype.content.install`.
+- Add :func:`sprockets.mixins.mediatype.content.get_settings`.
 
 `2.1.0`_ (16 Mar 2016)
 ----------------------

sprockets/mixins/mediatype/content.py

@@ -31,6 +31,7 @@ from . import handlers
 
 
 logger = logging.getLogger(__name__)
+SETTINGS_KEY = 'sprockets.mixins.mediatype.ContentSettings'
 
 
 class ContentSettings(object):
@@ -103,9 +104,7 @@ class ContentSettings(object):
     @classmethod
     def from_application(cls, application):
         """Retrieve the content settings from an application."""
-        if not hasattr(application, '_content_settings'):
-            setattr(application, '_content_settings', cls())
-        return application._content_settings
+        return get_settings(application, force_instance=True)
 
     @property
     def available_content_types(self):
@@ -119,6 +118,48 @@ class ContentSettings(object):
         return self._available_types
 
 
+def install(application, default_content_type, encoding=None):
+    """
+    Install the media type management settings.
+
+    :param tornado.web.Application application: the application to
+        install a :class:`.ContentSettings` object into.
+    :param str|NoneType default_content_type:
+    :param str|NoneType encoding:
+
+    :returns: the content settings instance
+    :rtype: sprockets.mixins.mediatype.content.ContentSettings
+
+    """
+    try:
+        settings = application.settings[SETTINGS_KEY]
+    except KeyError:
+        settings = application.settings[SETTINGS_KEY] = ContentSettings()
+        settings.default_content_type = default_content_type
+        settings.default_encoding = encoding
+    return settings
+
+
+def get_settings(application, force_instance=False):
+    """
+    Retrieve the media type settings for a application.
+
+    :param tornado.web.Application application:
+    :keyword bool force_instance: if :data:`True` then create the
+        instance if it does not exist
+
+    :return: the content settings instance
+    :rtype: sprockets.mixins.mediatype.content.ContentSettings
+
+    """
+    try:
+        return application.settings[SETTINGS_KEY]
+    except KeyError:
+        if not force_instance:
+            return None
+    return install(application, None)
+
+
 def add_binary_content_type(application, content_type, pack, unpack):
     """
     Add handler for a binary content type.

tests.py

@@ -30,7 +30,8 @@ class UTC(datetime.tzinfo):
 
 class Context(object):
     """Super simple class to call setattr on"""
-    pass
+    def __init__(self):
+        self.settings = {}
 
 
 def pack_string(obj):
@@ -262,6 +263,26 @@ class ContentFunctionTests(unittest.TestCase):
         transcoder = settings['application/json']
         self.assertIsInstance(transcoder, handlers.TextContentHandler)
 
+    def test_that_install_creates_settings(self):
+        settings = content.install(self.context, 'application/json', 'utf8')
+        self.assertIsNotNone(settings)
+        self.assertEqual(settings.default_content_type, 'application/json')
+        self.assertEqual(settings.default_encoding, 'utf8')
+
+    def test_that_get_settings_returns_none_when_no_settings(self):
+        settings = content.get_settings(self.context)
+        self.assertIsNone(settings)
+
+    def test_that_get_settings_returns_installed_settings(self):
+        settings = content.install(self.context, 'application/xml', 'utf8')
+        other_settings = content.get_settings(self.context)
+        self.assertIs(settings, other_settings)
+
+    def test_that_get_settings_will_create_instance_if_requested(self):
+        settings = content.get_settings(self.context, force_instance=True)
+        self.assertIsNotNone(settings)
+        self.assertIs(content.get_settings(self.context), settings)
+
 
 class MsgPackTranscoderTests(unittest.TestCase):