extend blacklist/whitelist syntax (#2025)

Each entry in such a list can now also include a subcategory
'<category>:<subcategory>'
and it is possible to use '*' or an empty string as placeholder
'*:<subcategory>', ':<subcategory>', '<category>:*'

For example
  "blacklist": "imgur,*:tag,gfycat:user" or
  "blacklist": ["imgur", "*:tag", "gfycat:user"]
will filter all 'imgur' extractors, all extractors  with a 'tag'
subcategory (e.g. https://danbooru.donmai.us/posts?tags=bonocho),
and all 'gfycat' user extractors.

test/test_util.py

@@ -357,6 +357,58 @@ class TestOther(unittest.TestCase):
         with self.assertRaises(exception.StopExtraction):
             expr()
 
+    def test_extractor_filter(self):
+        # empty
+        func = util.build_extractor_filter("")
+        self.assertEqual(func(TestExtractor)      , True)
+        self.assertEqual(func(TestExtractorParent), True)
+        self.assertEqual(func(TestExtractorAlt)   , True)
+
+        # category
+        func = util.build_extractor_filter("test_category")
+        self.assertEqual(func(TestExtractor)      , False)
+        self.assertEqual(func(TestExtractorParent), False)
+        self.assertEqual(func(TestExtractorAlt)   , True)
+
+        # subcategory
+        func = util.build_extractor_filter("*:test_subcategory")
+        self.assertEqual(func(TestExtractor)      , False)
+        self.assertEqual(func(TestExtractorParent), True)
+        self.assertEqual(func(TestExtractorAlt)   , False)
+
+        # basecategory
+        func = util.build_extractor_filter("test_basecategory")
+        self.assertEqual(func(TestExtractor)      , False)
+        self.assertEqual(func(TestExtractorParent), False)
+        self.assertEqual(func(TestExtractorAlt)   , False)
+
+        # category-subcategory pair
+        func = util.build_extractor_filter("test_category:test_subcategory")
+        self.assertEqual(func(TestExtractor)      , False)
+        self.assertEqual(func(TestExtractorParent), True)
+        self.assertEqual(func(TestExtractorAlt)   , True)
+
+        # combination
+        func = util.build_extractor_filter(
+            ["test_category", "*:test_subcategory"])
+        self.assertEqual(func(TestExtractor)      , False)
+        self.assertEqual(func(TestExtractorParent), False)
+        self.assertEqual(func(TestExtractorAlt)   , False)
+
+        # whitelist
+        func = util.build_extractor_filter(
+            "test_category:test_subcategory", negate=False)
+        self.assertEqual(func(TestExtractor)      , True)
+        self.assertEqual(func(TestExtractorParent), False)
+        self.assertEqual(func(TestExtractorAlt)   , False)
+
+        func = util.build_extractor_filter(
+            ["test_category:test_subcategory", "*:test_subcategory_parent"],
+            negate=False)
+        self.assertEqual(func(TestExtractor)      , True)
+        self.assertEqual(func(TestExtractorParent), True)
+        self.assertEqual(func(TestExtractorAlt)   , False)
+
     def test_generate_token(self):
         tokens = set()
         for _ in range(100):
@@ -469,5 +521,21 @@ class TestOther(unittest.TestCase):
         self.assertIs(obj["key"], obj)
 
 
+class TestExtractor():
+    category = "test_category"
+    subcategory = "test_subcategory"
+    basecategory = "test_basecategory"
+
+
+class TestExtractorParent(TestExtractor):
+    category = "test_category"
+    subcategory = "test_subcategory_parent"
+
+
+class TestExtractorAlt(TestExtractor):
+    category = "test_category_alt"
+    subcategory = "test_subcategory"
+
+
 if __name__ == '__main__':
     unittest.main()