Fix backwards-compatibility for users who explicitly set _BASE settings

scrapy/settings/__init__.py

@@ -116,9 +116,9 @@ def get(self, name, default=None):
     def getbool(self, name, default=False):
         """
         Get a setting value as a boolean.
-        
+
         ``1``, ``'1'``, and ``True`` return ``True``, while ``0``, ``'0'``,
-        ``False`` and ``None`` return ``False``. 
+        ``False`` and ``None`` return ``False``.
 
         For example, settings populated through environment variables set to
         ``'0'`` will return ``False`` when using this method.
@@ -203,8 +203,15 @@ def _getcomposite(self, name):
         if basename in self:
             warnings.warn('_BASE settings are deprecated.',
                           category=ScrapyDeprecationWarning)
-            compsett = BaseSettings(self[name + "_BASE"], priority='default')
-            compsett.update(self[name])
+            # When users defined a _BASE setting, they explicitly don't want to
+            # use any of Scrapy's defaults. Therefore, we only use these entries
+            # from self[name] (where the defaults now live) that have a priority
+            # higher than 'default'
+            compsett = BaseSettings(self[basename], priority='default')
+            for k in self[name]:
+                prio = self[name].getpriority(k)
+                if prio > get_settings_priority('default'):
+                    compsett.set(k, self[name][k], prio)
             return compsett
         else:
             return self[name]

tests/test_settings/__init__.py

@@ -252,12 +252,18 @@ def test_getpriority(self):
 
     def test_getcomposite(self):
         s = BaseSettings({'TEST_BASE': {1: 1, 2: 2},
-                          'TEST': BaseSettings({1: 10}),
-                          'HASNOBASE': BaseSettings({1: 1})})
+                          'TEST': BaseSettings({1: 10, 3: 30}, 'default'),
+                          'HASNOBASE': BaseSettings({1: 1}, 'default')})
+        s['TEST'].set(4, 4, priority='project')
+        # When users specify a _BASE setting they explicitly don't want to use
+        # Scrapy's defaults, so we don't want to see anything that has a
+        # 'default' priority from TEST
         cs = s._getcomposite('TEST')
-        self.assertEqual(len(cs), 2)
-        self.assertEqual(cs[1], 10)
+        print cs
+        self.assertEqual(len(cs), 3)
+        self.assertEqual(cs[1], 1)
         self.assertEqual(cs[2], 2)
+        self.assertEqual(cs[4], 4)
         cs = s._getcomposite('HASNOBASE')
         self.assertEqual(len(cs), 1)
         self.assertEqual(cs[1], 1)