Flat-Playlist JSON on Youtube doesn't contain valid url entries

[Shroompow]

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

(JSON formatted for readability)

On Youtube:

$ youtube-dl -v --flat-playlist -J https://www.youtube.com/playlist?list=PLPsW6g4Ef2HezVeZPfSq3U_sJLTVWENTs
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: ['-v', '--flat-playlist', '-J', 'https://www.youtube.com/playlist?list=PLPsW6g4Ef2HezVeZPfSq3U_sJLTVWENTs']
[debug] Encodings: locale cp1252, fs mbcs, out cp1252, pref cp1252
[debug] youtube-dl version 2020.03.24
[debug] Python version 3.4.4 (CPython) - Windows-7-6.1.7601-SP1
[debug] exe versions: ffmpeg N-91589-ge0539f0349, ffprobe N-91589-ge0539f0349, rtmpdump 2.4
[debug] Proxy map: {}
{
	"webpage_url_basename": "playlist",
	"webpage_url": "https://www.youtube.com/playlist?list=PLPsW6g4Ef2HezVeZPfSq3U_sJLTVWENTs",
	"extractor_key": "YoutubePlaylist",
	"uploader": "ShroomPow",
	"uploader_id": "UCjZ1x35ZeFmkTR9KrAIZR9g",
	"title": "test",
	"extractor": "youtube:playlist",
	"_type": "playlist",
	"uploader_url": "https://www.youtube.com/channel/UCjZ1x35ZeFmkTR9KrAIZR9g",
	"id": "PLPsW6g4Ef2HezVeZPfSq3U_sJLTVWENTs",
	"entries": [
		{
			"ie_key": "Youtube",
			"_type": "url",
			"title": "NieR Replicant ver.1.22474487139.../\u30cb\u30fc\u30a2 \u30ec\u30d7\u30ea\u30ab\u30f3\u30c8 ver.1.22474487139...: \u30c6\u30a3\u30b6\u30fc\u30c8\u30ec\u30fc\u30e9\u30fc",
			"id": "_sdn1B0N4k0",
			"url": "_sdn1B0N4k0"
		},
		{
			"ie_key": "Youtube",
			"_type": "url",
			"title": "NieR Re[in]carnation \uff08\u30cb\u30fc\u30a2 \u30ea\u30a3\u30f3\u30ab\u30fc\u30cd\u30fc\u30b7\u30e7\u30f3\uff09: TEASER TRAILER",
			"id": "DqGmbdO3u7o",
			"url": "DqGmbdO3u7o"
		}
	]
}

On Soundcloud:

$ youtube-dl -v --flat-playlist -J https://soundcloud.com/shroompow/tracks
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: ['-v', '--flat-playlist', '-J', 'https://soundcloud.com/shroompow/tracks']
[debug] Encodings: locale cp1252, fs mbcs, out cp1252, pref cp1252
[debug] youtube-dl version 2020.03.24
[debug] Python version 3.4.4 (CPython) - Windows-7-6.1.7601-SP1
[debug] exe versions: ffmpeg N-91589-ge0539f0349, ffprobe N-91589-ge0539f0349, rtmpdump 2.4
[debug] Proxy map: {}
{
	"entries": [
		{
			"url": "https://soundcloud.com/shroompow/cherry-storm",
			"ie_key": "Soundcloud",
			"id": "500350203",
			"_type": "url",
			"title": "Cherry Storm"
		},
		{
			"url": "https://soundcloud.com/shroompow/infernali-descensus-post",
			"ie_key": "Soundcloud",
			"id": "494275674",
			"_type": "url",
			"title": "Infernali Descensus"
		},
		{
			"url": "https://soundcloud.com/shroompow/infinity-shard",
			"ie_key": "Soundcloud",
			"id": "433506099",
			"_type": "url",
			"title": "Infinity Shard"
		},
		{
			"url": "https://soundcloud.com/shroompow/overcoming-the-dust",
			"ie_key": "Soundcloud",
			"id": "429594621",
			"_type": "url",
			"title": "Overcoming The Dust"
		},
		{
			"url": "https://soundcloud.com/shroompow/nano-desert",
			"ie_key": "Soundcloud",
			"id": "378427388",
			"_type": "url",
			"title": "Nano Desert"
		},
		{
			"url": "https://soundcloud.com/shroompow/crystallized-shadows-on-frozen-cables",
			"ie_key": "Soundcloud",
			"id": "371238884",
			"_type": "url",
			"title": "Crystallized Shadows On Frozen Cables"
		},
		{
			"url": "https://soundcloud.com/shroompow/netted-sky",
			"ie_key": "Soundcloud",
			"id": "371236970",
			"_type": "url",
			"title": "Netted Sky"
		}
	],
	"webpage_url_basename": "tracks",
	"extractor_key": "SoundcloudUser",
	"_type": "playlist",
	"title": "Shroompow (Tracks)",
	"webpage_url": "https://soundcloud.com/shroompow/tracks",
	"id": "328107961",
	"extractor": "soundcloud:user"
}

Description

When extracting playlist JSON using --flat-playlist -J on Youtube the url-property of its entries don't contain a valid url. Instead they contain the video-id. This isn't the case on two other extractors i tested (bandcamp and soundcloud).

When extracting playlist JSON without --flat-playlist the entries contain a valid url in the webpage-property. This however significantly increases execution time, especially on large playlists.

Is this intended behaviour? Should i be able to rely on the url-property to be valid unless the extraction failed?

[dstftw]

This is expected behavior. url may be anything that is recognized by youtube-dl.