extend and rename util.CustomNone

gallery_dl/util.py

@@ -528,8 +528,8 @@ def parse_inputfile(file, log):
                 yield line
 
 
-class UniversalNone():
-    """None-style object that supports more operations than None itself"""
+class CustomNone():
+    """None-style type that supports more operations than regular None"""
     __slots__ = ()
 
     def __getattribute__(self, _):
@@ -538,10 +538,28 @@ class UniversalNone():
     def __getitem__(self, _):
         return self
 
+    def __iter__(self):
+        return self
+
+    def __call__(self, *args, **kwargs):
+        return self
+
+    @staticmethod
+    def __next__():
+        raise StopIteration
+
     @staticmethod
     def __bool__():
         return False
 
+    @staticmethod
+    def __len__():
+        return 0
+
+    @staticmethod
+    def __format__(_):
+        return "None"
+
     @staticmethod
     def __str__():
         return "None"
@@ -549,7 +567,7 @@ class UniversalNone():
     __repr__ = __str__
 
 
-NONE = UniversalNone()
+NONE = CustomNone()
 EPOCH = datetime.datetime(1970, 1, 1)
 SECOND = datetime.timedelta(0, 1)
 WINDOWS = (os.name == "nt")

test/test_util.py

@@ -618,10 +618,21 @@ class TestOther(unittest.TestCase):
         obj = util.NONE
 
         self.assertFalse(obj)
+        self.assertEqual(len(obj), 0)
         self.assertEqual(str(obj), str(None))
         self.assertEqual(repr(obj), repr(None))
+        self.assertEqual(format(obj), str(None))
+        self.assertEqual(format(obj, "%F"), str(None))
         self.assertIs(obj.attr, obj)
         self.assertIs(obj["key"], obj)
+        self.assertIs(obj(), obj)
+        self.assertIs(obj(1, "a"), obj)
+        self.assertIs(obj(foo="bar"), obj)
+
+        i = 0
+        for _ in obj:
+            i += 1
+        self.assertEqual(i, 0)
 
 
 class TestExtractor():