Apply dist_thresh to Genius and Google backends

This commit introduces a distance threshold mechanism for the Genius and
Google backends.

- Create a new `SearchBackend` base class with a method `check_match`
  that performs checking.
- Start using undocumented `dist_thresh` configuration option for good,
  and mention it in the docs. This controls the maximum allowable
  distance for matching artist and title names.

These changes aim to improve the accuracy of lyrics matching, especially
when there are slight variations in artist or title names, see #4791.

beetsplug/lyrics.py

@@ -16,7 +16,6 @@
 
 from __future__ import annotations
 
-import difflib
 import errno
 import itertools
 import json
@@ -25,7 +24,7 @@
 import struct
 import unicodedata
 import warnings
-from functools import partial
+from functools import cached_property, partial
 from typing import ClassVar
 from urllib.parse import quote, urlencode
 
@@ -50,6 +49,7 @@
 
 import beets
 from beets import plugins, ui
+from beets.autotag.hooks import string_dist
 
 DIV_RE = re.compile(r"<(/?)div>?", re.I)
 COMMENT_RE = re.compile(r"<!--.*-->", re.S)
@@ -345,15 +345,43 @@ def fetch(self, artist, title, album=None, length=None):
         return lyrics
 
 
-class Genius(Backend):
+class SearchBackend(Backend):
+    REQUIRES_BS = True
+
+    @cached_property
+    def dist_thresh(self) -> float:
+        return self.config["dist_thresh"].get(float)
+
+    def check_match(
+        self, target_artist: str, target_title: str, artist: str, title: str
+    ) -> bool:
+        """Check if the given artist and title are 'good enough' match."""
+        max_dist = max(
+            string_dist(target_artist, artist),
+            string_dist(target_title, title),
+        )
+        if round(max_dist, 2) <= self.dist_thresh:
+            return True
+
+        self._log.warning(
+            "({}, {}) pair does not match ({}, {}), dist {:.2f} > expected {:.2f}",
+            artist,
+            title,
+            target_artist,
+            target_title,
+            max_dist,
+            self.dist_thresh,
+        )
+        return False
+
+
+class Genius(SearchBackend):
     """Fetch lyrics from Genius via genius-api.
 
     Simply adapted from
     bigishdata.com/2016/09/27/getting-song-lyrics-from-geniuss-api-scraping/
     """
 
-    REQUIRES_BS = True
-
     base_url = "https://api.genius.com"
 
     def __init__(self, config, log):
@@ -376,19 +404,15 @@ def fetch(self, artist, title, album=None, length=None):
             self._log.debug("Genius API request returned invalid JSON")
             return None
 
-        # find a matching artist in the json
+        check = partial(self.check_match, artist, title)
         for hit in json["response"]["hits"]:
-            hit_artist = hit["result"]["primary_artist"]["name"]
-
-            if slug(hit_artist) == slug(artist):
-                html = self.fetch_url(hit["result"]["url"])
+            result = hit["result"]
+            if check(result["primary_artist"]["name"], result["title"]):
+                html = self.fetch_url(result["url"])
                 if not html:
                     return None
                 return self._scrape_lyrics_from_html(html)
 
-        self._log.debug(
-            "Genius failed to find a matching artist for '{0}'", artist
-        )
         return None
 
     def _search(self, artist, title):
@@ -582,16 +606,9 @@ def is_text_notcode(text):
         return None
 
 
-class Google(Backend):
+class Google(SearchBackend):
     """Fetch lyrics from Google search results."""
 
-    REQUIRES_BS = True
-
-    def __init__(self, config, log):
-        super().__init__(config, log)
-        self.api_key = config["google_API_key"].as_str()
-        self.engine_id = config["google_engine_ID"].as_str()
-
     def is_lyrics(self, text, artist=None):
         """Determine whether the text seems to be valid lyrics."""
         if not text:
@@ -637,20 +654,21 @@ def slugify(self, text):
     BY_TRANS = ["by", "par", "de", "von"]
     LYRICS_TRANS = ["lyrics", "paroles", "letras", "liedtexte"]
 
-    def is_page_candidate(self, url_link, url_title, title, artist):
+    def is_page_candidate(
+        self, artist: str, title: str, url_link: str, url_title: str
+    ) -> bool:
         """Return True if the URL title makes it a good candidate to be a
         page that contains lyrics of title by artist.
         """
-        title = self.slugify(title.lower())
+        title_slug = self.slugify(title.lower())
+        url_title_slug = self.slugify(url_title.lower())
+        if title_slug in url_title_slug:
+            return True
+
         artist = self.slugify(artist.lower())
         sitename = re.search(
             "//([^/]+)/.*", self.slugify(url_link.lower())
         ).group(1)
-        url_title = self.slugify(url_title.lower())
-
-        # Check if URL title contains song title (exact match)
-        if url_title.find(title) != -1:
-            return True
 
         # or try extracting song title from URL title and check if
         # they are close enough
@@ -660,18 +678,15 @@ def is_page_candidate(self, url_link, url_title, title, artist):
             + self.LYRICS_TRANS
         )
         tokens = [re.escape(t) for t in tokens]
-        song_title = re.sub("(%s)" % "|".join(tokens), "", url_title)
+        song_title = re.sub("(%s)" % "|".join(tokens), "", url_title_slug)
 
-        song_title = song_title.strip("_|")
-        typo_ratio = 0.9
-        ratio = difflib.SequenceMatcher(None, song_title, title).ratio()
-        return ratio >= typo_ratio
+        return self.check_match(artist, title_slug, artist, song_title)
 
     def fetch(self, artist, title, album=None, length=None):
         query = f"{artist} {title}"
         url = "https://www.googleapis.com/customsearch/v1?key=%s&cx=%s&q=%s" % (
-            self.api_key,
-            self.engine_id,
+            self.config["google_API_key"].as_str(),
+            self.config["google_engine_ID"].as_str(),
             quote(query.encode("utf-8")),
         )
 
@@ -688,24 +703,21 @@ def fetch(self, artist, title, album=None, length=None):
             self._log.debug("google backend error: {0}", reason)
             return None
 
-        if "items" in data.keys():
-            for item in data["items"]:
-                url_link = item["link"]
-                url_title = item.get("title", "")
-                if not self.is_page_candidate(
-                    url_link, url_title, title, artist
-                ):
-                    continue
-                html = self.fetch_url(url_link)
-                if not html:
-                    continue
-                lyrics = scrape_lyrics_from_html(html)
-                if not lyrics:
-                    continue
-
-                if self.is_lyrics(lyrics, artist):
-                    self._log.debug("got lyrics from {0}", item["displayLink"])
-                    return lyrics
+        check_candidate = partial(self.is_page_candidate, artist, title)
+        for item in data.get("items", []):
+            url_link = item["link"]
+            if not check_candidate(url_link, item.get("title", "")):
+                continue
+            html = self.fetch_url(url_link)
+            if not html:
+                continue
+            lyrics = scrape_lyrics_from_html(html)
+            if not lyrics:
+                continue
+
+            if self.is_lyrics(lyrics, artist):
+                self._log.debug("got lyrics from {0}", item["displayLink"])
+                return lyrics
 
         return None
 
@@ -729,6 +741,7 @@ def __init__(self):
                 "bing_client_secret": None,
                 "bing_lang_from": [],
                 "bing_lang_to": None,
+                "dist_thresh": 0.11,
                 "google_API_key": None,
                 "google_engine_ID": "009217259823014548361:lndtuqkycfu",
                 "genius_api_key": "Ryq93pUGm8bM6eUWwD_M3NOFFDAtp2yEE7W"
@@ -740,7 +753,6 @@ def __init__(self):
                 # Musixmatch is disabled by default as they are currently blocking
                 # requests with the beets user agent.
                 "sources": [s for s in self.SOURCES if s != "musixmatch"],
-                "dist_thresh": 0.1,
             }
         )
         self.config["bing_client_secret"].redact = True

docs/changelog.rst

@@ -47,6 +47,9 @@ Bug fixes:
 * :doc:`plugins/lyrics`: Update ``tekstowo`` backend to fetch lyrics directly
   since recent updates to their website made it unsearchable.
   :bug:`5456`
+* :doc:`plugins/lyrics`: Fix the issue with ``genius`` backend not being able
+  to match lyrics when there was a slight variation in the artist name.
+  :bug:`4791`
 
 For packagers:
 

docs/plugins/lyrics.rst

@@ -42,6 +42,12 @@ configuration file. The available options are:
   Default: ``[]``
 - **bing_lang_to**: Language to translate lyrics into.
   Default: None.
+- **dist_thresh**: The maximum distance between the artist and title
+  combination of the music file and lyrics candidate to consider them a match.
+  Lower values will make the plugin more strict, higher values will make it
+  more lenient. This does not apply to the ``lrclib`` backend as it matches
+  durations.
+  Default: ``0.11``.
 - **fallback**: By default, the file will be left unchanged when no lyrics are
   found. Use the empty string ``''`` to reset the lyrics in such a case.
   Default: None.

test/plugins/test_lyrics.py

@@ -18,7 +18,7 @@
 import os
 import re
 import unittest
-from unittest.mock import MagicMock, patch
+from unittest.mock import patch
 
 import confuse
 import pytest
@@ -31,11 +31,12 @@
 from beetsplug import lyrics
 
 log = logging.getLogger("beets.test_lyrics")
-raw_backend = lyrics.Backend({}, log)
-google = lyrics.Google(MagicMock(), log)
-genius = lyrics.Genius(MagicMock(), log)
-tekstowo = lyrics.Tekstowo(MagicMock(), log)
-lrclib = lyrics.LRCLib(MagicMock(), log)
+plugin = lyrics.LyricsPlugin()
+raw_backend = lyrics.Backend(plugin.config, log)
+google = lyrics.Google(plugin.config, log)
+genius = lyrics.Genius(plugin.config, log)
+tekstowo = lyrics.Tekstowo(plugin.config, log)
+lrclib = lyrics.LRCLib(plugin.config, log)
 
 
 class LyricsPluginTest(unittest.TestCase):
@@ -244,6 +245,42 @@ def setUp(self):
             self.skipTest("Beautiful Soup 4 not available")
 
 
+class TestSearchBackend:
+    @pytest.fixture
+    def backend(self, dist_thresh):
+        plugin = lyrics.LyricsPlugin()
+        plugin.config.set({"dist_thresh": dist_thresh})
+        return lyrics.SearchBackend(plugin.config, plugin._log)
+
+    @pytest.mark.parametrize(
+        "dist_thresh, target_artist, artist, should_match",
+        [
+            (0.11, "Target Artist", "Target Artist", True),
+            (0.11, "Target Artist", "Target Artis", True),
+            (0.11, "Target Artist", "Target Arti", False),
+            (0.11, "Psychonaut", "Psychonaut (BEL)", True),
+            (0.11, "beets song", "beats song", True),
+            (0.10, "beets song", "beats song", False),
+            (
+                0.11,
+                "Lucid Dreams (Forget Me)",
+                "Lucid Dreams (Remix) ft. Lil Uzi Vert",
+                False,
+            ),
+            (
+                0.12,
+                "Lucid Dreams (Forget Me)",
+                "Lucid Dreams (Remix) ft. Lil Uzi Vert",
+                True,
+            ),
+        ],
+    )
+    def test_check_match(self, backend, target_artist, artist, should_match):
+        assert (
+            backend.check_match(target_artist, "", artist, "") == should_match
+        )
+
+
 class LyricsPluginSourcesTest(LyricsGoogleBaseTest, LyricsAssertions):
     """Check that beets google custom search engine sources are correctly
     scraped.
@@ -400,7 +437,7 @@ def test_is_page_candidate_exact_match(self):
             html, "html.parser", parse_only=SoupStrainer("title")
         )
         assert google.is_page_candidate(
-            url, soup.title.string, s["title"], s["artist"]
+            s["artist"], s["title"], url, soup.title.string
         ), url
 
     def test_is_page_candidate_fuzzy_match(self):
@@ -413,12 +450,12 @@ def test_is_page_candidate_fuzzy_match(self):
 
         # very small diffs (typo) are ok eg 'beats' vs 'beets' with same artist
         assert google.is_page_candidate(
-            url, url_title, s["title"], s["artist"]
+            s["artist"], s["title"], url, url_title
         ), url
         # reject different title
         url_title = "example.com | seets bong lyrics by John doe"
         assert not google.is_page_candidate(
-            url, url_title, s["title"], s["artist"]
+            s["artist"], s["title"], url, url_title
         ), url
 
     def test_is_page_candidate_special_chars(self):
@@ -430,7 +467,7 @@ def test_is_page_candidate_special_chars(self):
         url = s["url"] + s["path"]
         url_title = "foo"
 
-        google.is_page_candidate(url, url_title, s["title"], "Sunn O)))")
+        google.is_page_candidate("Sunn O)))", s["title"], url, url_title)
 
 
 # test Genius backend
@@ -506,12 +543,14 @@ def test_json(self, mock_fetch_url, mock_scrape):
                                     "name": "\u200bblackbear",
                                 },
                                 "url": "blackbear_url",
+                                "title": "Idfc",
                             }
                         },
                         {
                             "result": {
                                 "primary_artist": {"name": "El\u002dp"},
                                 "url": "El-p_url",
+                                "title": "Idfc",
                             }
                         },
                     ]