YoutubePlaylists pages can sometimes refer to their contents via /watch?v=...&list=<id> rather than /playlist?list=<id>

[mmirate]

Checklist

• I'm reporting a broken site support
• I've verified that I'm running youtube-dl version 2020.03.24
• I've checked that all provided URLs are alive and playable in a browser
• I've checked that all URLs and arguments with special characters are properly quoted or escaped
• I've searched the bugtracker for similar issues including closed ones

Verbose log

[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: ['-v', 'https://www.youtube.com/channel/UCPlYCdARxfOHlMUaA4b8a_A/playlists?view=50&flow=list&shelf_id=17666223384013636041']
[debug] Encodings: locale UTF-8, fs utf-8, out utf-8, pref UTF-8
[debug] youtube-dl version 2020.03.24
[debug] Python version 3.8.2 (CPython) - Linux-4.19.114-1-ARCH-armv7l-with-glibc2.4
[debug] exe versions: ffmpeg 4.2.2, ffprobe 4.2.2
[debug] Proxy map: {}
[youtube:playlists] UCPlYCdARxfOHlMUaA4b8a_A: Downloading webpage
[download] Downloading playlist: Benny Green - Topic
[youtube:playlists] playlist Benny Green - Topic: Downloading 0 videos
[download] Finished downloading playlist: Benny Green - Topic

Description

The YoutubePlaylists extractor seems to be expecting lists of playlists to refer to their contained playlists via a link to the full playlist (/playlist?list=...) inside each h3.yt-lockup-title element. However, pages such as the exemplar https://www.youtube.com/channel/UCPlYCdARxfOHlMUaA4b8a_A/playlists?view=50&flow=list&shelf_id=17666223384013636041, even when &disable_polymer=true is added to the URL, instead have the h3.yt-lockup-title contain a link to the first video in the playlist with the playlist id included (/watch?v=...&list=...). This causes YoutubePlaylists's regex to not match anything, resulting in youtube-dl downloading nothing from the shelf.

I've attached a --dump-pages output of the same URL, to illustrate:

UCPlYCdARxfOHlMUaA4b8a_A_https_-_www.youtube.com_channel_UCPlYCdARxfOHlMUaA4b8a_A_playlistsview=50_flow=list_shelf_id=17666223384013636041_disable_polymer=true.dump.txt

[willbeaufoy]

Strange, I'm having no problems downloading that playlist. But where is yt-lockup-title meant to be? It doesn't appear anywhere in the source of the channel page you linked to when I view it in my browser.

[mmirate]

That's really strange. Here's what I see in my browser:

... which seems congruent with the relevant portions of the --dump-pages output that youtube-dl gets me.

[willbeaufoy]

Oh yeah I got the yt-lockup-title when I disabled polymer, however it's not in my dump whether I disable polymer or not oddly - and the download works in both cases.