[utils] `traverse_obj`: Fix more bugs

and cleanup uses of `default=[]`

Continued from b1bde57bef

test/test_utils.py

@@ -2000,7 +2000,7 @@ Line 1
 
         # Test Ellipsis behavior
         self.assertCountEqual(traverse_obj(_TEST_DATA, ...),
-                              (item for item in _TEST_DATA.values() if item not in (None, [], {})),
+                              (item for item in _TEST_DATA.values() if item not in (None, {})),
                               msg='`...` should give all non discarded values')
         self.assertCountEqual(traverse_obj(_TEST_DATA, ('urls', 0, ...)), _TEST_DATA['urls'][0].values(),
                               msg='`...` selection for dicts should select all values')
@@ -2095,7 +2095,7 @@ Line 1
                          msg='remove empty values when nested dict key fails')
         self.assertEqual(traverse_obj(None, {0: 'fail'}), {},
                          msg='default to dict if pruned')
-        self.assertEqual(traverse_obj(None, {0: 'fail'}, default=...), {},
+        self.assertEqual(traverse_obj(None, {0: 'fail'}, default=...), {0: ...},
                          msg='default to dict if pruned and default is given')
         self.assertEqual(traverse_obj(_TEST_DATA, {0: {0: 'fail'}}, default=...), {0: {0: ...}},
                          msg='use nested `default` when nested dict key fails and `default`')
@@ -2124,34 +2124,55 @@ Line 1
                          msg='if branched but not successful return `[]`, not `default`')
         self.assertEqual(traverse_obj(_DEFAULT_DATA, ('list', ...)), [],
                          msg='if branched but object is empty return `[]`, not `default`')
+        self.assertEqual(traverse_obj(None, ...), [],
+                         msg='if branched but object is `None` return `[]`, not `default`')
+        self.assertEqual(traverse_obj({0: None}, (0, ...)), [],
+                         msg='if branched but state is `None` return `[]`, not `default`')
+
+        branching_paths = [
+            ('fail', ...),
+            (..., 'fail'),
+            100 * ('fail',) + (...,),
+            (...,) + 100 * ('fail',),
+        ]
+        for branching_path in branching_paths:
+            self.assertEqual(traverse_obj({}, branching_path), [],
+                             msg='if branched but state is `None`, return `[]` (not `default`)')
+            self.assertEqual(traverse_obj({}, 'fail', branching_path), [],
+                             msg='if branching in last alternative and previous did not match, return `[]` (not `default`)')
+            self.assertEqual(traverse_obj({0: 'x'}, 0, branching_path), 'x',
+                             msg='if branching in last alternative and previous did match, return single value')
+            self.assertEqual(traverse_obj({0: 'x'}, branching_path, 0), 'x',
+                             msg='if branching in first alternative and non-branching path does match, return single value')
+            self.assertEqual(traverse_obj({}, branching_path, 'fail'), None,
+                             msg='if branching in first alternative and non-branching path does not match, return `default`')
 
         # Testing expected_type behavior
         _EXPECTED_TYPE_DATA = {'str': 'str', 'int': 0}
-        self.assertEqual(traverse_obj(_EXPECTED_TYPE_DATA, 'str', expected_type=str), 'str',
-                         msg='accept matching `expected_type` type')
-        self.assertEqual(traverse_obj(_EXPECTED_TYPE_DATA, 'str', expected_type=int), None,
-                         msg='reject non matching `expected_type` type')
-        self.assertEqual(traverse_obj(_EXPECTED_TYPE_DATA, 'int', expected_type=lambda x: str(x)), '0',
-                         msg='transform type using type function')
-        self.assertEqual(traverse_obj(_EXPECTED_TYPE_DATA, 'str',
-                                      expected_type=lambda _: 1 / 0), None,
-                         msg='wrap expected_type fuction in try_call')
-        self.assertEqual(traverse_obj(_EXPECTED_TYPE_DATA, ..., expected_type=str), ['str'],
-                         msg='eliminate items that expected_type fails on')
-        self.assertEqual(traverse_obj(_TEST_DATA, {0: 100, 1: 1.2}, expected_type=int), {0: 100},
-                         msg='type as expected_type should filter dict values')
-        self.assertEqual(traverse_obj(_TEST_DATA, {0: 100, 1: 1.2, 2: 'None'}, expected_type=str_or_none), {0: '100', 1: '1.2'},
-                         msg='function as expected_type should transform dict values')
-        self.assertEqual(traverse_obj(_TEST_DATA, ({0: 1.2}, 0, {int_or_none}), expected_type=int), 1,
-                         msg='expected_type should not filter non final dict values')
-        self.assertEqual(traverse_obj(_TEST_DATA, {0: {0: 100, 1: 'str'}}, expected_type=int), {0: {0: 100}},
-                         msg='expected_type should transform deep dict values')
-        self.assertEqual(traverse_obj(_TEST_DATA, [({0: '...'}, {0: '...'})], expected_type=type(...)), [{0: ...}, {0: ...}],
-                         msg='expected_type should transform branched dict values')
-        self.assertEqual(traverse_obj({1: {3: 4}}, [(1, 2), 3], expected_type=int), [4],
-                         msg='expected_type regression for type matching in tuple branching')
-        self.assertEqual(traverse_obj(_TEST_DATA, ['data', ...], expected_type=int), [],
-                         msg='expected_type regression for type matching in dict result')
+        self.assertEqual(traverse_obj(_EXPECTED_TYPE_DATA, 'str', expected_type=str),
+                         'str', msg='accept matching `expected_type` type')
+        self.assertEqual(traverse_obj(_EXPECTED_TYPE_DATA, 'str', expected_type=int),
+                         None, msg='reject non matching `expected_type` type')
+        self.assertEqual(traverse_obj(_EXPECTED_TYPE_DATA, 'int', expected_type=lambda x: str(x)),
+                         '0', msg='transform type using type function')
+        self.assertEqual(traverse_obj(_EXPECTED_TYPE_DATA, 'str', expected_type=lambda _: 1 / 0),
+                         None, msg='wrap expected_type fuction in try_call')
+        self.assertEqual(traverse_obj(_EXPECTED_TYPE_DATA, ..., expected_type=str),
+                         ['str'], msg='eliminate items that expected_type fails on')
+        self.assertEqual(traverse_obj(_TEST_DATA, {0: 100, 1: 1.2}, expected_type=int),
+                         {0: 100}, msg='type as expected_type should filter dict values')
+        self.assertEqual(traverse_obj(_TEST_DATA, {0: 100, 1: 1.2, 2: 'None'}, expected_type=str_or_none),
+                         {0: '100', 1: '1.2'}, msg='function as expected_type should transform dict values')
+        self.assertEqual(traverse_obj(_TEST_DATA, ({0: 1.2}, 0, {int_or_none}), expected_type=int),
+                         1, msg='expected_type should not filter non final dict values')
+        self.assertEqual(traverse_obj(_TEST_DATA, {0: {0: 100, 1: 'str'}}, expected_type=int),
+                         {0: {0: 100}}, msg='expected_type should transform deep dict values')
+        self.assertEqual(traverse_obj(_TEST_DATA, [({0: '...'}, {0: '...'})], expected_type=type(...)),
+                         [{0: ...}, {0: ...}], msg='expected_type should transform branched dict values')
+        self.assertEqual(traverse_obj({1: {3: 4}}, [(1, 2), 3], expected_type=int),
+                         [4], msg='expected_type regression for type matching in tuple branching')
+        self.assertEqual(traverse_obj(_TEST_DATA, ['data', ...], expected_type=int),
+                         [], msg='expected_type regression for type matching in dict result')
 
         # Test get_all behavior
         _GET_ALL_DATA = {'key': [0, 1, 2]}

yt_dlp/downloader/fragment.py

@@ -383,7 +383,7 @@ class FragmentFD(FileDownloader):
         max_workers = self.params.get('concurrent_fragment_downloads', 1)
         if max_progress > 1:
             self._prepare_multiline_status(max_progress)
-        is_live = any(traverse_obj(args, (..., 2, 'is_live'), default=[]))
+        is_live = any(traverse_obj(args, (..., 2, 'is_live')))
 
         def thread_func(idx, ctx, fragments, info_dict, tpe):
             ctx['max_progress'] = max_progress

yt_dlp/extractor/abematv.py

@@ -416,7 +416,7 @@ class AbemaTVIE(AbemaTVBaseIE):
                 f'https://api.abema.io/v1/video/programs/{video_id}', video_id,
                 note='Checking playability',
                 headers=headers)
-            ondemand_types = traverse_obj(api_response, ('terms', ..., 'onDemandType'), default=[])
+            ondemand_types = traverse_obj(api_response, ('terms', ..., 'onDemandType'))
             if 3 not in ondemand_types:
                 # cannot acquire decryption key for these streams
                 self.report_warning('This is a premium-only stream')
@@ -489,7 +489,7 @@ class AbemaTVTitleIE(AbemaTVBaseIE):
             })
         yield from (
             self.url_result(f'https://abema.tv/video/episode/{x}')
-            for x in traverse_obj(programs, ('programs', ..., 'id'), default=[]))
+            for x in traverse_obj(programs, ('programs', ..., 'id')))
 
     def _entries(self, playlist_id, series_version):
         return OnDemandPagedList(

yt_dlp/extractor/gamejolt.py

@@ -48,7 +48,7 @@ class GameJoltBaseIE(InfoExtractor):
                 post_hash_id, note='Downloading comments list page %d' % page)
             if not comments_data.get('comments'):
                 break
-            for comment in traverse_obj(comments_data, (('comments', 'childComments'), ...), expected_type=dict, default=[]):
+            for comment in traverse_obj(comments_data, (('comments', 'childComments'), ...), expected_type=dict):
                 yield {
                     'id': comment['id'],
                     'text': self._parse_content_as_text(

yt_dlp/extractor/iqiyi.py

@@ -585,7 +585,7 @@ class IqIE(InfoExtractor):
                     'langCode': self._get_cookie('lang', 'en_us'),
                     'deviceId': self._get_cookie('QC005', '')
                 }, fatal=False)
-            ut_list = traverse_obj(vip_data, ('data', 'all_vip', ..., 'vipType'), expected_type=str_or_none, default=[])
+            ut_list = traverse_obj(vip_data, ('data', 'all_vip', ..., 'vipType'), expected_type=str_or_none)
         else:
             ut_list = ['0']
 
@@ -617,7 +617,7 @@ class IqIE(InfoExtractor):
             self.report_warning('This preview video is limited%s' % format_field(preview_time, None, ' to %s seconds'))
 
         # TODO: Extract audio-only formats
-        for bid in set(traverse_obj(initial_format_data, ('program', 'video', ..., 'bid'), expected_type=str_or_none, default=[])):
+        for bid in set(traverse_obj(initial_format_data, ('program', 'video', ..., 'bid'), expected_type=str_or_none)):
             dash_path = dash_paths.get(bid)
             if not dash_path:
                 self.report_warning(f'Unknown format id: {bid}. It is currently not being extracted')
@@ -628,7 +628,7 @@ class IqIE(InfoExtractor):
                 fatal=False), 'data', expected_type=dict)
 
             video_format = traverse_obj(format_data, ('program', 'video', lambda _, v: str(v['bid']) == bid),
-                                        expected_type=dict, default=[], get_all=False) or {}
+                                        expected_type=dict, get_all=False) or {}
             extracted_formats = []
             if video_format.get('m3u8Url'):
                 extracted_formats.extend(self._extract_m3u8_formats(
@@ -669,7 +669,7 @@ class IqIE(InfoExtractor):
                 })
             formats.extend(extracted_formats)
 
-        for sub_format in traverse_obj(initial_format_data, ('program', 'stl', ...), expected_type=dict, default=[]):
+        for sub_format in traverse_obj(initial_format_data, ('program', 'stl', ...), expected_type=dict):
             lang = self._LID_TAGS.get(str_or_none(sub_format.get('lid')), sub_format.get('_name'))
             subtitles.setdefault(lang, []).extend([{
                 'ext': format_ext,

yt_dlp/extractor/panopto.py

@@ -412,7 +412,7 @@ class PanoptoIE(PanoptoBaseIE):
         return {
             'id': video_id,
             'title': delivery.get('SessionName'),
-            'cast': traverse_obj(delivery, ('Contributors', ..., 'DisplayName'), default=[], expected_type=lambda x: x or None),
+            'cast': traverse_obj(delivery, ('Contributors', ..., 'DisplayName'), expected_type=lambda x: x or None),
             'timestamp': session_start_time - 11640000000 if session_start_time else None,
             'duration': delivery.get('Duration'),
             'thumbnail': base_url + f'/Services/FrameGrabber.svc/FrameRedirect?objectId={video_id}&mode=Delivery&random={random()}',
@@ -563,7 +563,7 @@ class PanoptoListIE(PanoptoBaseIE):
             base_url, '/Services/Data.svc/GetFolderInfo', folder_id,
             data={'folderID': folder_id}, fatal=False)
         return {
-            'title': get_first(response, 'Name', default=[])
+            'title': get_first(response, 'Name')
         }
 
     def _real_extract(self, url):

yt_dlp/extractor/patreon.py

@@ -310,7 +310,7 @@ class PatreonIE(PatreonBaseIE):
                 f'posts/{post_id}/comments', post_id, query=params, note='Downloading comments page %d' % page)
 
             cursor = None
-            for comment in traverse_obj(response, (('data', ('included', lambda _, v: v['type'] == 'comment')), ...), default=[]):
+            for comment in traverse_obj(response, (('data', ('included', lambda _, v: v['type'] == 'comment')), ...)):
                 count += 1
                 comment_id = comment.get('id')
                 attributes = comment.get('attributes') or {}

yt_dlp/extractor/tiktok.py

@@ -285,7 +285,7 @@ class TikTokBaseIE(InfoExtractor):
         user_url = self._UPLOADER_URL_FORMAT % (traverse_obj(author_info,
                                                              'sec_uid', 'id', 'uid', 'unique_id',
                                                              expected_type=str_or_none, get_all=False))
-        labels = traverse_obj(aweme_detail, ('hybrid_label', ..., 'text'), expected_type=str, default=[])
+        labels = traverse_obj(aweme_detail, ('hybrid_label', ..., 'text'), expected_type=str)
 
         contained_music_track = traverse_obj(
             music_info, ('matched_song', 'title'), ('matched_pgc_sound', 'title'), expected_type=str)
@@ -355,7 +355,7 @@ class TikTokBaseIE(InfoExtractor):
                 'ext': 'mp4',
                 'width': width,
                 'height': height,
-            } for url in traverse_obj(play_url, (..., 'src'), expected_type=url_or_none, default=[]) if url]
+            } for url in traverse_obj(play_url, (..., 'src'), expected_type=url_or_none) if url]
 
         download_url = url_or_none(video_info.get('downloadAddr')) or traverse_obj(video_info, ('download', 'url'), expected_type=url_or_none)
         if download_url:

yt_dlp/extractor/youtube.py

@@ -745,7 +745,7 @@ class YoutubeBaseInfoExtractor(InfoExtractor):
         }
 
         badges = []
-        for badge in traverse_obj(renderer, ('badges', ..., 'metadataBadgeRenderer'), default=[]):
+        for badge in traverse_obj(renderer, ('badges', ..., 'metadataBadgeRenderer')):
             badge_type = (
                 privacy_icon_map.get(traverse_obj(badge, ('icon', 'iconType'), expected_type=str))
                 or badge_style_map.get(traverse_obj(badge, 'style'))
@@ -785,7 +785,7 @@ class YoutubeBaseInfoExtractor(InfoExtractor):
                     runs = item
 
                 runs = runs[:min(len(runs), max_runs or len(runs))]
-                text = ''.join(traverse_obj(runs, (..., 'text'), expected_type=str, default=[]))
+                text = ''.join(traverse_obj(runs, (..., 'text'), expected_type=str))
                 if text:
                     return text
 
@@ -805,7 +805,7 @@ class YoutubeBaseInfoExtractor(InfoExtractor):
         """
         thumbnails = []
         for path in path_list or [()]:
-            for thumbnail in traverse_obj(data, (*variadic(path), 'thumbnails', ...), default=[]):
+            for thumbnail in traverse_obj(data, (*variadic(path), 'thumbnails', ...)):
                 thumbnail_url = url_or_none(thumbnail.get('url'))
                 if not thumbnail_url:
                     continue
@@ -2668,11 +2668,10 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 return
 
             _, _, prs, player_url = self._download_player_responses(url, smuggled_data, video_id, webpage_url)
-            video_details = traverse_obj(
-                prs, (..., 'videoDetails'), expected_type=dict, default=[])
+            video_details = traverse_obj(prs, (..., 'videoDetails'), expected_type=dict)
             microformats = traverse_obj(
                 prs, (..., 'microformat', 'playerMicroformatRenderer'),
-                expected_type=dict, default=[])
+                expected_type=dict)
             _, live_status, _, formats, _ = self._list_formats(video_id, microformats, video_details, prs, player_url)
             is_live = live_status == 'is_live'
             start_time = time.time()
@@ -3173,7 +3172,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
         content_list = traverse_obj(
             data,
             ('engagementPanels', ..., 'engagementPanelSectionListRenderer', 'content', 'macroMarkersListRenderer', 'contents'),
-            expected_type=list, default=[])
+            expected_type=list)
         chapter_time = lambda chapter: parse_duration(self._get_text(chapter, 'timeDescription'))
         chapter_title = lambda chapter: self._get_text(chapter, 'title')
 
@@ -3450,7 +3449,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
         if traverse_obj(player_response, ('playabilityStatus', 'desktopLegacyAgeGateReason')):
             return True
 
-        reasons = traverse_obj(player_response, ('playabilityStatus', ('status', 'reason')), default=[])
+        reasons = traverse_obj(player_response, ('playabilityStatus', ('status', 'reason')))
         AGE_GATE_REASONS = (
             'confirm your age', 'age-restricted', 'inappropriate',  # reason
             'age_verification_required', 'age_check_required',  # status
@@ -3606,7 +3605,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
             'audio_quality_ultralow', 'audio_quality_low', 'audio_quality_medium', 'audio_quality_high',  # Audio only formats
             'small', 'medium', 'large', 'hd720', 'hd1080', 'hd1440', 'hd2160', 'hd2880', 'highres'
         ])
-        streaming_formats = traverse_obj(streaming_data, (..., ('formats', 'adaptiveFormats'), ...), default=[])
+        streaming_formats = traverse_obj(streaming_data, (..., ('formats', 'adaptiveFormats'), ...))
 
         for fmt in streaming_formats:
             if fmt.get('targetDurationSec'):
@@ -3872,7 +3871,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                        else 'was_live' if live_content
                        else 'not_live' if False in (is_live, live_content)
                        else None)
-        streaming_data = traverse_obj(player_responses, (..., 'streamingData'), default=[])
+        streaming_data = traverse_obj(player_responses, (..., 'streamingData'))
         *formats, subtitles = self._extract_formats_and_subtitles(streaming_data, video_id, player_url, live_status, duration)
 
         return live_broadcast_details, live_status, streaming_data, formats, subtitles
@@ -3887,7 +3886,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
         webpage, master_ytcfg, player_responses, player_url = self._download_player_responses(url, smuggled_data, video_id, webpage_url)
 
         playability_statuses = traverse_obj(
-            player_responses, (..., 'playabilityStatus'), expected_type=dict, default=[])
+            player_responses, (..., 'playabilityStatus'), expected_type=dict)
 
         trailer_video_id = get_first(
             playability_statuses,
@@ -3900,11 +3899,10 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
         search_meta = ((lambda x: self._html_search_meta(x, webpage, default=None))
                        if webpage else (lambda x: None))
 
-        video_details = traverse_obj(
-            player_responses, (..., 'videoDetails'), expected_type=dict, default=[])
+        video_details = traverse_obj(player_responses, (..., 'videoDetails'), expected_type=dict)
         microformats = traverse_obj(
             player_responses, (..., 'microformat', 'playerMicroformatRenderer'),
-            expected_type=dict, default=[])
+            expected_type=dict)
 
         translated_title = self._get_text(microformats, (..., 'title'))
         video_title = (self._preferred_lang and translated_title
@@ -4110,10 +4108,10 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
             # Converted into dicts to remove duplicates
             captions = {
                 get_lang_code(sub): sub
-                for sub in traverse_obj(pctr, (..., 'captionTracks', ...), default=[])}
+                for sub in traverse_obj(pctr, (..., 'captionTracks', ...))}
             translation_languages = {
                 lang.get('languageCode'): self._get_text(lang.get('languageName'), max_runs=1)
-                for lang in traverse_obj(pctr, (..., 'translationLanguages', ...), default=[])}
+                for lang in traverse_obj(pctr, (..., 'translationLanguages', ...))}
 
             def process_language(container, base_url, lang_code, sub_name, query):
                 lang_subs = container.setdefault(lang_code, [])
@@ -4267,9 +4265,8 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                     list) or []):
                 tbrs = variadic(
                     traverse_obj(
-                        tlb, 'toggleButtonRenderer',
-                        ('segmentedLikeDislikeButtonRenderer', ..., 'toggleButtonRenderer'),
-                        default=[]))
+                        tlb, ('toggleButtonRenderer', ...),
+                        ('segmentedLikeDislikeButtonRenderer', ..., 'toggleButtonRenderer')))
                 for tbr in tbrs:
                     for getter, regex in [(
                             lambda x: x['defaultText']['accessibility']['accessibilityData'],

yt_dlp/utils.py

@@ -5420,7 +5420,7 @@ def traverse_obj(
     Each of the provided `paths` is tested and the first producing a valid result will be returned.
     The next path will also be tested if the path branched but no results could be found.
     Supported values for traversal are `Mapping`, `Sequence` and `re.Match`.
-    Unhelpful values (`[]`, `{}`, `None`) are treated as the absence of a value and discarded.
+    Unhelpful values (`{}`, `None`) are treated as the absence of a value and discarded.
 
     The paths will be wrapped in `variadic`, so that `'key'` is conveniently the same as `('key', )`.
 
@@ -5484,7 +5484,7 @@ def traverse_obj(
         branching = False
         result = None
 
-        if obj is None:
+        if obj is None and traverse_string:
             pass
 
         elif key is None:
@@ -5558,14 +5558,13 @@ def traverse_obj(
                 result = next((v for k, v in obj.groupdict().items() if casefold(k) == key), None)
 
         elif isinstance(key, (int, slice)):
-            if not is_sequence(obj):
-                if traverse_string:
-                    with contextlib.suppress(IndexError):
-                        result = str(obj)[key]
-            else:
+            if is_sequence(obj):
                 branching = isinstance(key, slice)
                 with contextlib.suppress(IndexError):
                     result = obj[key]
+            elif traverse_string:
+                with contextlib.suppress(IndexError):
+                    result = str(obj)[key]
 
         return branching, result if branching else (result,)
 
@@ -5617,7 +5616,7 @@ def traverse_obj(
 
     def _traverse_obj(obj, path, allow_empty, test_type):
         results, has_branched, is_dict = apply_path(obj, path, test_type)
-        results = LazyList(item for item in results if item not in (None, [], {}))
+        results = LazyList(item for item in results if item not in (None, {}))
         if get_all and has_branched:
             if results:
                 return results.exhaust()