#863: derive YouTube track artist from music fields / -Topic channel / 'Artist - Title' instead of the playlist owner

core/youtube_track_meta.py

@@ -0,0 +1,91 @@
+"""Derive a track's artist + title from a yt-dlp playlist entry.
+
+Flat playlist extraction (used to dodge YouTube rate limits) gives sparse
+per-entry data: often just ``title``, ``id``, ``duration``, and an
+``uploader``/``channel`` that — for a playlist like "Likes" — is the PLAYLIST
+OWNER, not the track artist. GitHub #863: every track came out as the owner
+("Wing It"), or "Unknown Artist" when ``uploader`` was absent, because the
+parser used ``entry['uploader']`` as the artist.
+
+The artist is usually recoverable from one of, in priority order:
+
+1. yt-dlp music-metadata fields (``artists`` / ``artist`` / ``creator``),
+   populated for YouTube Music tracks.
+2. An auto-generated ``"<Artist> - Topic"`` channel name.
+3. The classic ``"<Artist> - <Title>"`` form embedded in the video title.
+
+This module is the single, pure place that decides which signal wins, so the
+precedence is unit-testable instead of buried in the web_server endpoint. It
+deliberately does NOT fall back to the channel/uploader as the artist — on a
+playlist that's the owner, and mislabelling every track is worse than an honest
+"Unknown Artist" (which downstream MusicBrainz discovery can still try to fix).
+"""
+
+from __future__ import annotations
+
+import re
+from typing import Any, Mapping, Tuple
+
+# Trailing "- Topic" on an auto-generated YouTube Music channel.
+_TOPIC_RE = re.compile(r'\s*-\s*topic\s*$', re.IGNORECASE)
+
+# "Artist - Title": a hyphen/en-dash/em-dash flanked by spaces, both sides
+# non-empty. Splits on the FIRST such separator so "A - B (C Remix)" → ("A",
+# "B (C Remix)"). Spaces around the dash are required so hyphenated names like
+# "Jean-Michel Jarre" aren't split.
+_TITLE_SPLIT_RE = re.compile(r'^\s*(?P<artist>.+?)\s+[-–—]\s+(?P<title>.+?)\s*$')
+
+
+def _first_music_field(entry: Mapping[str, Any]) -> str:
+    """First non-empty value from yt-dlp's music-metadata fields."""
+    artists = entry.get('artists')
+    if isinstance(artists, (list, tuple)):
+        for a in artists:
+            s = str(a or '').strip()
+            if s:
+                return s
+    for key in ('artist', 'creator'):
+        v = entry.get(key)
+        if isinstance(v, str) and v.strip():
+            return v.strip()
+    return ''
+
+
+def derive_artist_and_title(entry: Mapping[str, Any]) -> Tuple[str, str]:
+    """Return ``(artist, title)`` from a yt-dlp (flat) playlist entry.
+
+    ``artist`` is ``''`` when no reliable signal exists — the caller defaults
+    that to "Unknown Artist" rather than using the playlist owner's channel
+    (#863). ``title`` is the raw video title, except when an "Artist - Title"
+    split provided the artist, in which case it's the right-hand side.
+    """
+    if not isinstance(entry, Mapping):
+        return '', 'Unknown Track'
+
+    title = str(entry.get('title') or '').strip() or 'Unknown Track'
+
+    # 1. Music-metadata fields (YouTube Music).
+    field_artist = _first_music_field(entry)
+    if field_artist:
+        return field_artist, title
+
+    # 2. "<Artist> - Topic" auto-channel — the channel name IS the artist.
+    channel = str(entry.get('uploader') or entry.get('channel') or '').strip()
+    if _TOPIC_RE.search(channel):
+        stripped = _TOPIC_RE.sub('', channel).strip()
+        if stripped:
+            return stripped, title
+
+    # 3. "<Artist> - <Title>" embedded in the title.
+    m = _TITLE_SPLIT_RE.match(title)
+    if m:
+        artist = m.group('artist').strip()
+        rest = m.group('title').strip()
+        if artist and rest:
+            return artist, rest
+
+    # 4. No reliable artist signal — caller defaults to "Unknown Artist".
+    return '', title
+
+
+__all__ = ['derive_artist_and_title']

tests/test_youtube_track_meta.py

@@ -0,0 +1,94 @@
+"""Seam tests for YouTube playlist artist/title derivation (GitHub #863).
+
+Flat playlist extraction gives sparse entries; the parser used to take the
+artist straight from `uploader`, which on a playlist is the OWNER — so every
+track came out as "Wing It" / "Unknown Artist". `derive_artist_and_title` picks
+the best available signal instead. These pin the precedence + the
+"never use the playlist owner" guarantee.
+"""
+
+from __future__ import annotations
+
+from core.youtube_track_meta import derive_artist_and_title
+
+
+def test_music_artists_field_wins():
+    artist, title = derive_artist_and_title(
+        {'title': 'Forgiven', 'artists': ['Within Temptation'], 'uploader': 'Wing It'})
+    assert artist == 'Within Temptation'
+    assert title == 'Forgiven'
+
+
+def test_artist_field_used_when_no_artists_list():
+    artist, title = derive_artist_and_title(
+        {'title': 'Alive', 'artist': 'Empire of the Sun', 'uploader': 'Wing It'})
+    assert artist == 'Empire of the Sun'
+    assert title == 'Alive'
+
+
+def test_topic_channel_is_the_artist():
+    artist, title = derive_artist_and_title(
+        {'title': 'Revolte', 'uploader': 'Paul Kalkbrenner - Topic'})
+    assert artist == 'Paul Kalkbrenner'
+    assert title == 'Revolte'
+
+
+def test_artist_title_split_from_title():
+    # The exact #863 log case — title carries "Artist - Track", uploader is the
+    # playlist owner.
+    artist, title = derive_artist_and_title(
+        {'title': 'Paul Kalkbrenner - Revolte (Original Mix) [Bpitch]', 'uploader': 'Wing It'})
+    assert artist == 'Paul Kalkbrenner'
+    # Splits on the FIRST separator; the remainder keeps the qualifiers for the
+    # title cleaner to strip downstream.
+    assert title == 'Revolte (Original Mix) [Bpitch]'
+
+
+def test_no_signal_returns_empty_artist_not_playlist_owner():
+    # The unrecoverable case: plain title, uploader is the owner. Must NOT label
+    # the track with the owner's channel (#863).
+    artist, title = derive_artist_and_title(
+        {'title': 'Forgiven', 'uploader': 'Wing It'})
+    assert artist == ''
+    assert title == 'Forgiven'
+
+
+def test_hyphenated_name_without_spaces_not_split():
+    # "Jean-Michel Jarre" has no spaced dash → not an Artist-Title split.
+    artist, title = derive_artist_and_title({'title': 'Jean-Michel Jarre', 'uploader': 'Wing It'})
+    assert artist == ''
+    assert title == 'Jean-Michel Jarre'
+
+
+def test_en_dash_separator_splits():
+    artist, title = derive_artist_and_title({'title': 'Koven – Worlds Apart'})  # en dash
+    assert artist == 'Koven'
+    assert title == 'Worlds Apart'
+
+
+def test_topic_beats_title_split_but_cleaner_handles_prefix():
+    # Topic channel present AND title repeats "Artist - Title": topic wins for the
+    # artist; the full title is returned for the downstream cleaner to de-prefix.
+    artist, title = derive_artist_and_title(
+        {'title': 'Paul Kalkbrenner - Revolte', 'uploader': 'Paul Kalkbrenner - Topic'})
+    assert artist == 'Paul Kalkbrenner'
+    assert title == 'Paul Kalkbrenner - Revolte'
+
+
+def test_missing_title_is_safe():
+    artist, title = derive_artist_and_title({'uploader': 'Wing It'})
+    assert artist == ''
+    assert title == 'Unknown Track'
+
+
+def test_bad_input_is_safe():
+    assert derive_artist_and_title(None) == ('', 'Unknown Track')
+    assert derive_artist_and_title("not a dict") == ('', 'Unknown Track')
+
+
+def test_empty_artists_list_falls_through():
+    # An empty/blank artists list must not win — fall through to the title split.
+    artist, title = derive_artist_and_title(
+        {'title': 'Koven - Worlds Apart', 'artists': ['', None]})
+    assert artist == 'Koven'
+    assert title == 'Worlds Apart'

web_server.py

@@ -14742,6 +14742,7 @@ def parse_youtube_playlist(url):
     Uses flat playlist extraction to avoid rate limits and get all tracks
     Returns a list of track dictionaries compatible with our Track structure
     """
+    from core.youtube_track_meta import derive_artist_and_title
     try:
         # Configure yt-dlp options for flat playlist extraction (avoids rate limits)
         ydl_opts = {
@@ -14774,13 +14775,24 @@ def parse_youtube_playlist(url):
                 
                 # Extract basic information from flat extraction
                 raw_title = entry.get('title', 'Unknown Track')
-                raw_uploader = entry.get('uploader', 'Unknown Artist')
+                raw_uploader = entry.get('uploader') or entry.get('channel') or ''
                 duration = entry.get('duration', 0)
                 video_id = entry.get('id', '')
 
-                # Clean the track title and artist using our cleaning functions
-                cleaned_artist = clean_youtube_artist(raw_uploader)
-                cleaned_title = clean_youtube_track_title(raw_title, cleaned_artist)
+                # Derive the artist from the best available signal — music
+                # fields, a "- Topic" channel, or an "Artist - Title" split —
+                # instead of blindly using `uploader`, which on a playlist is the
+                # OWNER, not the track artist (#863: every track became "Wing It"
+                # / "Unknown Artist"). Returns ('' , title) when nothing reliable.
+                derived_artist, derived_title = derive_artist_and_title(entry)
+
+                # Clean the track title and artist using our cleaning functions.
+                if derived_artist:
+                    cleaned_artist = clean_youtube_artist(derived_artist)
+                    cleaned_title = clean_youtube_track_title(derived_title, cleaned_artist)
+                else:
+                    cleaned_artist = 'Unknown Artist'
+                    cleaned_title = clean_youtube_track_title(derived_title, None)
 
                 # Create track object matching GUI structure
                 track_data = {
@@ -14789,7 +14801,7 @@ def parse_youtube_playlist(url):
                     'artists': [cleaned_artist],
                     'duration_ms': duration * 1000 if duration else 0,
                     'raw_title': raw_title,  # Keep original for reference
-                    'raw_artist': raw_uploader,  # Keep original for reference
+                    'raw_artist': derived_artist or raw_uploader,  # Keep original for reference
                     'url': f"https://www.youtube.com/watch?v={video_id}"
                 }