feat(music): save lyrics beside the audio and keep song fields over remote

Song.lyrics_suffix writes the lyrics file; song fields set in get_tracks now reach a remote client.

docs/dev/service-architecture.md

@@ -197,8 +197,10 @@ Each subclass adds its own required fields on top of `id_` and `service`:
 
     A `Song` also takes optional metadata keywords that the tagger and the naming templates
     read: `album_artist`, `release_type`, `total_tracks`, `total_discs`, `genre`,
-    `explicit`, `isrc`, `upc`, `copyright`, `label`, `lyrics`, and `artwork_url`. Read the
-    class for the current list.
+    `explicit`, `isrc`, `upc`, `copyright`, `label`, `lyrics`, `lyrics_suffix`, and
+    `artwork_url`. Read the class for the current list. With `lyrics_suffix` (`".lrc"`,
+    `".ttml"`), unshackle also saves `lyrics` beside the final audio file under that suffix.
+    You can set these fields in `get_tracks()` too, and a remote client gets them back.
 
     The tagger also falls back to `Song.data` for fields the constructor did not get, such
     as the composer or a full release date. It reads the top level of that dict and a

docs/guide/output-and-naming.md

@@ -269,6 +269,10 @@ unshackle writes lyrics when the service supplies them: a `LYRICS` Vorbis commen
 `USLT` frame for MP3, and a `©lyr` atom for M4A. Ogg uses the same `LYRICS` field as
 FLAC. unshackle does not write synchronized lyrics (`SYLT`).
 
+A service can also ask for a lyrics file beside the audio, for example
+`08.Get.Lucky.lrc` next to `08.Get.Lucky.m4a`. A music player reads the timed lines from
+it. The file also comes back to the client from a remote server.
+
 A metadata fault does not stop the run. The file is already in place, so unshackle writes a
 warning and continues.
 

tests/core/test_load_tracks_enrich.py

@@ -42,3 +42,10 @@ def test_a_song_takes_only_the_language():
     song = Song(id_="song-0001", service=SERVICE, name="Track 1", artist="A", album="B", track=1, disc=1, year=1999)
     apply_enrich(song, "The Gold Seekers", 2017, Language.get("es"))
     assert (song.name, song.year, str(song.language)) == ("Track 1", 1999, "es")
+
+
+def test_a_song_takes_the_lyrics_set_in_get_tracks():
+    song = Song(id_="song-0001", service=SERVICE, name="Track 1", artist="A", album="B", track=1, disc=1)
+    info = {"name": "Track 1", "lyrics": "[00:01.00]Line", "lyrics_suffix": ".lrc"}
+    load_tracks(refreshing_service(info), song)
+    assert (song.lyrics, song.lyrics_suffix) == ("[00:01.00]Line", ".lrc")

unshackle/commands/dl.py

@@ -3867,6 +3867,11 @@ class dl:
                             )
                         if include_sample:
                             self.write_sample(final_path, title, media_info)
+                        if isinstance(title, Song) and title.lyrics and title.lyrics_suffix:
+                            lyrics_path = final_path.with_suffix(title.lyrics_suffix)
+                            lyrics_path.write_text(f"{title.lyrics}\n", encoding="utf-8")
+                            sidecar_files.setdefault(muxed_path, []).append(lyrics_path)
+                            self.log.info(f"Saved lyrics to {lyrics_path.name}")
 
                         post_script_context = build_context(
                             title,

unshackle/core/api/handlers.py

@@ -34,6 +34,7 @@ from unshackle.core.proxies.resolve import initialize_proxy_providers, resolve_p
 from unshackle.core.services import Services
 from unshackle.core.session import utf8_text
 from unshackle.core.titles import Episode, Movie, Song, Title_T
+from unshackle.core.titles.music import SONG_FIELDS
 from unshackle.core.tracks import Audio, Subtitle, Tracks, Video
 from unshackle.core.utilities import declared_kwargs, kind_only_conflict
 from unshackle.core.utils.click_types import AUDIO_CODEC_LIST, SUBTITLE_CODEC, VIDEO_CODEC_LIST
@@ -1158,24 +1159,7 @@ def serialize_title(title: Title_T) -> Dict[str, Any]:
         if getattr(title, "daily", None) is not None:
             result["daily"] = title.daily
     if is_song:
-        for field in (
-            "artist",
-            "album",
-            "track",
-            "disc",
-            "album_artist",
-            "release_type",
-            "total_tracks",
-            "total_discs",
-            "genre",
-            "explicit",
-            "isrc",
-            "upc",
-            "copyright",
-            "label",
-            "lyrics",
-            "artwork_url",
-        ):
+        for field in SONG_FIELDS:
             result[field] = getattr(title, field, None)
     if isinstance(title, (Episode, Movie)) and getattr(title, "anime", None) is not None:
         result["anime"] = title.anime

unshackle/core/remote_service.py

@@ -44,7 +44,7 @@ from unshackle.core.session import MAX_BACKOFF
 from unshackle.core.titles import Title_T, Titles_T, remap_titles
 from unshackle.core.titles.episode import Episode, Series
 from unshackle.core.titles.movie import Movie, Movies
-from unshackle.core.titles.music import Album, Song
+from unshackle.core.titles.music import SONG_FIELDS, Album, Song
 from unshackle.core.tracks import Audio, Chapter, Chapters, Subtitle, Tracks, Video
 from unshackle.core.tracks.attachment import Attachment
 from unshackle.core.tracks.track import Track
@@ -599,7 +599,7 @@ def apply_title_fields(title: Title_T, info: Dict[str, Any]) -> None:
     elif info.get("name"):
         title.name = info["name"]
 
-    for key in ("anime", "daily"):
+    for key in ("anime", "daily", *(SONG_FIELDS if isinstance(title, Song) else ())):
         if info.get(key) is not None:
             setattr(title, key, info[key])
 
@@ -654,6 +654,7 @@ def build_title(info: Dict[str, Any], service_tag: str, fallback_id: str) -> Tit
             label=info.get("label"),
             lyrics=info.get("lyrics"),
             artwork_url=info.get("artwork_url"),
+            lyrics_suffix=info.get("lyrics_suffix"),
         )
     else:
         raise click.ClickException(

unshackle/core/titles/music.py

@@ -12,6 +12,27 @@ from unshackle.core.titles.title import Title
 from unshackle.core.utilities import sanitize_filename
 from unshackle.core.utils.template_formatter import TemplateFormatter, detect_spacer
 
+SONG_FIELDS = (
+    "artist",
+    "album",
+    "track",
+    "disc",
+    "album_artist",
+    "release_type",
+    "total_tracks",
+    "total_discs",
+    "genre",
+    "explicit",
+    "isrc",
+    "upc",
+    "copyright",
+    "label",
+    "lyrics",
+    "lyrics_suffix",
+    "artwork_url",
+)
+"""The `Song` attributes a remote session sends, beyond the fields every title has."""
+
 
 class Song(Title):
     def __init__(
@@ -38,7 +59,9 @@ class Song(Title):
         label: Optional[str] = None,
         lyrics: Optional[str] = None,
         artwork_url: Optional[str] = None,
+        lyrics_suffix: Optional[str] = None,
     ) -> None:
+        """`lyrics_suffix` (".lrc", ".ttml") also saves `lyrics` beside the audio file with that suffix."""
         super().__init__(id_, service, language, data)
 
         if not name:
@@ -90,6 +113,8 @@ class Song(Title):
             raise TypeError(f"Expected lyrics to be a str, not {lyrics!r}")
         if artwork_url is not None and not isinstance(artwork_url, str):
             raise TypeError(f"Expected artwork_url to be a str, not {artwork_url!r}")
+        if lyrics_suffix is not None and not (isinstance(lyrics_suffix, str) and lyrics_suffix.startswith(".")):
+            raise TypeError(f"Expected lyrics_suffix to be a str starting with '.', not {lyrics_suffix!r}")
 
         name = name.strip()
         artist = artist.strip()
@@ -135,6 +160,7 @@ class Song(Title):
         self.label = label
         self.lyrics = lyrics
         self.artwork_url = artwork_url
+        self.lyrics_suffix = lyrics_suffix
 
     def __str__(self) -> str:
         return "{artist} - {album} ({year}) / {track:02}. {name}".format(