arg_to_iter: return [arg] if arg is a dict

Signed-off-by: Ping Yin <pkufranky@gmail.com>

scrapy/tests/test_utils_misc.py

@@ -23,6 +23,7 @@ class UtilsMiscTestCase(unittest.TestCase):
         self.assertEqual(list(arg_to_iter(100)), [100])
         self.assertEqual(list(arg_to_iter(l for l in 'abc')), ['a', 'b', 'c'])
         self.assertEqual(list(arg_to_iter([1,2,3])), [1,2,3])
+        self.assertEqual(list(arg_to_iter({'a':1})), [{'a': 1}])
 
 if __name__ == "__main__":
     unittest.main()

scrapy/utils/misc.py

@@ -9,10 +9,12 @@ from scrapy.utils.markup import remove_entities
 def arg_to_iter(arg):
     """Convert an argument to an iterable. The argument can be a None, single
     value, or an iterable.
+
+    Exception: if arg is a dict, [arg] will be returned
     """
     if arg is None:
         return []
-    elif hasattr(arg, '__iter__'):
+    elif not isinstance(arg, dict) and hasattr(arg, '__iter__'):
         return arg
     else:
         return [arg]