Fix `playlist_index` not obeying `playlist_start`

and add tests
Closes #720

test/test_YoutubeDL.py

@@ -978,54 +978,31 @@ class TestYoutubeDL(unittest.TestCase):
             ydl.process_ie_result(copy.deepcopy(playlist))
             return ydl.downloaded_info_dicts
 
-        def get_ids(params):
-            return [int(v['id']) for v in get_downloaded_info_dicts(params)]
-
-        result = get_ids({})
-        self.assertEqual(result, [1, 2, 3, 4])
-
-        result = get_ids({'playlistend': 10})
-        self.assertEqual(result, [1, 2, 3, 4])
-
-        result = get_ids({'playlistend': 2})
-        self.assertEqual(result, [1, 2])
-
-        result = get_ids({'playliststart': 10})
-        self.assertEqual(result, [])
-
-        result = get_ids({'playliststart': 2})
-        self.assertEqual(result, [2, 3, 4])
-
-        result = get_ids({'playlist_items': '2-4'})
-        self.assertEqual(result, [2, 3, 4])
-
-        result = get_ids({'playlist_items': '2,4'})
-        self.assertEqual(result, [2, 4])
-
-        result = get_ids({'playlist_items': '10'})
-        self.assertEqual(result, [])
-
-        result = get_ids({'playlist_items': '3-10'})
-        self.assertEqual(result, [3, 4])
-
-        result = get_ids({'playlist_items': '2-4,3-4,3'})
-        self.assertEqual(result, [2, 3, 4])
+        def test_selection(params, expected_ids):
+            results = [
+                (v['playlist_autonumber'] - 1, (int(v['id']), v['playlist_index']))
+                for v in get_downloaded_info_dicts(params)]
+            self.assertEqual(results, list(enumerate(zip(expected_ids, expected_ids))))
+
+        test_selection({}, [1, 2, 3, 4])
+        test_selection({'playlistend': 10}, [1, 2, 3, 4])
+        test_selection({'playlistend': 2}, [1, 2])
+        test_selection({'playliststart': 10}, [])
+        test_selection({'playliststart': 2}, [2, 3, 4])
+        test_selection({'playlist_items': '2-4'}, [2, 3, 4])
+        test_selection({'playlist_items': '2,4'}, [2, 4])
+        test_selection({'playlist_items': '10'}, [])
 
         # Tests for https://github.com/ytdl-org/youtube-dl/issues/10591
-        # @{
-        result = get_downloaded_info_dicts({'playlist_items': '2-4,3-4,3'})
-        self.assertEqual(result[0]['playlist_index'], 2)
-        self.assertEqual(result[1]['playlist_index'], 3)
-
-        result = get_downloaded_info_dicts({'playlist_items': '2-4,3-4,3'})
-        self.assertEqual(result[0]['playlist_index'], 2)
-        self.assertEqual(result[1]['playlist_index'], 3)
-        self.assertEqual(result[2]['playlist_index'], 4)
-
-        result = get_downloaded_info_dicts({'playlist_items': '4,2'})
-        self.assertEqual(result[0]['playlist_index'], 4)
-        self.assertEqual(result[1]['playlist_index'], 2)
-        # @}
+        test_selection({'playlist_items': '2-4,3-4,3'}, [2, 3, 4])
+        test_selection({'playlist_items': '4,2'}, [4, 2])
+
+        # Tests for https://github.com/yt-dlp/yt-dlp/issues/720
+        # https://github.com/yt-dlp/yt-dlp/issues/302
+        test_selection({'playlistreverse': True}, [4, 3, 2, 1])
+        test_selection({'playliststart': 2, 'playlistreverse': True}, [4, 3, 2])
+        test_selection({'playlist_items': '2,4', 'playlistreverse': True}, [4, 2])
+        test_selection({'playlist_items': '4,2'}, [4, 2])
 
     def test_urlopen_no_file_protocol(self):
         # see https://github.com/ytdl-org/youtube-dl/issues/8227

yt_dlp/YoutubeDL.py

@@ -1452,7 +1452,7 @@ class YoutubeDL(object):
 
         # Save playlist_index before re-ordering
         entries = [
-            ((playlistitems[i - 1] if playlistitems else i), entry)
+            ((playlistitems[i - 1] if playlistitems else i + playliststart - 1), entry)
             for i, entry in enumerate(entries, 1)
             if entry is not None]
         n_entries = len(entries)
@@ -1517,7 +1517,7 @@ class YoutubeDL(object):
         max_failures = self.params.get('skip_playlist_after_errors') or float('inf')
         for i, entry_tuple in enumerate(entries, 1):
             playlist_index, entry = entry_tuple
-            if 'playlist_index' in self.params.get('compat_options', []):
+            if 'playlist-index' in self.params.get('compat_options', []):
                 playlist_index = playlistitems[i - 1] if playlistitems else i
             self.to_screen('[download] Downloading video %s of %s' % (i, n_entries))
             # This __x_forwarded_for_ip thing is a bit ugly but requires