Tidy up APISettings object to not rely on module state

rest_framework/settings.py

@@ -21,6 +21,8 @@ from django.conf import settings
 from django.utils import importlib
 
 
+USER_SETTINGS = getattr(settings, 'REST_FRAMEWORK', None)
+
 DEFAULTS = {
     'DEFAULT_RENDERERS': (
         'rest_framework.renderers.JSONRenderer',
@@ -76,22 +78,19 @@ IMPORT_STRINGS = (
 )
 
 
-def perform_import(val, setting):
+def perform_import(val, setting_name):
     """
     If the given setting is a string import notation,
     then perform the necessary import or imports.
     """
-    if val is None or not setting in IMPORT_STRINGS:
-        return val
-
     if isinstance(val, basestring):
-        return import_from_string(val, setting)
+        return import_from_string(val, setting_name)
     elif isinstance(val, (list, tuple)):
-        return [import_from_string(item, setting) for item in val]
+        return [import_from_string(item, setting_name) for item in val]
     return val
 
 
-def import_from_string(val, setting):
+def import_from_string(val, setting_name):
     """
     Attempt to import a class from a string representation.
     """
@@ -102,7 +101,7 @@ def import_from_string(val, setting):
         module = importlib.import_module(module_path)
         return getattr(module, class_name)
     except:
-        msg = "Could not import '%s' for API setting '%s'" % (val, setting)
+        msg = "Could not import '%s' for API setting '%s'" % (val, setting_name)
         raise ImportError(msg)
 
 
@@ -117,19 +116,28 @@ class APISettings(object):
     Any setting with string import paths will be automatically resolved
     and return the class, rather than the string literal.
     """
+    def __init__(self, user_settings=None, defaults=None, import_strings=None):
+        self.user_settings = user_settings or {}
+        self.defaults = defaults or {}
+        self.import_strings = import_strings or ()
+
     def __getattr__(self, attr):
-        if attr not in DEFAULTS.keys():
+        if attr not in self.defaults.keys():
             raise AttributeError("Invalid API setting: '%s'" % attr)
 
         try:
             # Check if present in user settings
-            val = perform_import(settings.REST_FRAMEWORK[attr], attr)
-        except (AttributeError, KeyError):
+            val = self.user_settings[attr]
+        except KeyError:
             # Fall back to defaults
-            val = perform_import(DEFAULTS[attr], attr)
+            val = self.defaults[attr]
+
+        # Coerce import strings into classes
+        if val and attr in self.import_strings:
+            val = perform_import(val, attr)
 
         # Cache the result
         setattr(self, attr, val)
         return val
 
-api_settings = APISettings()
+api_settings = APISettings(USER_SETTINGS, DEFAULTS, IMPORT_STRINGS)