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[extractor/youtube] Improve description parsing performance (#7315)

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* The parsing is skipped when not needed
* The regex is improved by simulating atomic groups with lookaheads

Authored by: pukkandan, berkanteber
This commit is contained in:
Berkan Teber 2023-06-22 10:27:54 +03:00 committed by GitHub
parent 98cb1eda7a
commit 71dc18fa29
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1 changed files with 11 additions and 5 deletions
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16
yt_dlp/extractor/youtube.py
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@ -4346,15 +4346,21 @@ def process_language(container, base_url, lang_code, sub_name, query):
info[d_k] = parse_duration(query[k][0])
# Youtube Music Auto-generated description
if video_description:
if (video_description or '').strip().endswith('\nAuto-generated by YouTube.'):
# XXX: Causes catastrophic backtracking if description has "·"
# E.g. https://www.youtube.com/watch?v=DoPaAxMQoiI
# Simulating atomic groups: (?P<a>[^xy]+)x => (?=(?P<a>[^xy]+))(?P=a)x
# reduces it, but does not fully fix it. https://regex101.com/r/8Ssf2h/2
mobj = re.search(
r'''(?xs)
(?P<track>[^·\n]+)·(?P<artist>[^\n]+)\n+
(?P<album>[^\n]+)
(?=(?P<track>[^\n·]+))(?P=track)·
(?=(?P<artist>[^\n]+))(?P=artist)\n+
(?=(?P<album>[^\n]+))(?P=album)\n
(?:.+?℗\s*(?P<release_year>\d{4})(?!\d))?
(?:.+?Released on\s*:\s*(?P<release_date>\d{4}-\d{2}-\d{2}))?
(.+?\nArtist\s*:\s*(?P<clean_artist>[^\n]+))?
.+\nAuto-generated\ by\ YouTube\.\s*$
(.+?\nArtist\s*:\s*
(?=(?P<clean_artist>[^\n]+))(?P=clean_artist)\n
)?.+\nAuto-generated\ by\ YouTube\.\s*$
''', video_description)
if mobj:
release_year = mobj.group('release_year')