internal/db/migrations/0087_library_rematch.down.sql

@@ -0,0 +1,2 @@
+-- Nothing to undo: the refused albums are matched again either way.
+SELECT 1;

internal/db/migrations/0087_library_rematch.up.sql

@@ -0,0 +1,9 @@
+-- The first matching (#5569) required every track's length to fit as well
+-- as its title, and refused singles and near-complete albums the library
+-- plainly holds. Matching now takes the titles alone under the album's own
+-- name: the albums it refused are matched again.
+DELETE FROM library_album_matches WHERE outcome = 'unmatched';
+
+UPDATE acquisition_settings
+   SET library_listed_at = NULL, library_unlisted = 0
+ WHERE library_listing_started_at IS NOT NULL;

internal/wanted/library_test.go

@@ -252,10 +252,22 @@ func TestTrackAgreement(t *testing.T) {
 		{"the right title at the wrong length", []libraryTrack{{Number: 2, Title: "Song", LengthMs: 400000}}, 0},
 		{"a track counted once", []libraryTrack{{Title: "Song", LengthMs: 200000}, {Title: "Song", LengthMs: 200000}}, 1},
 	} {
-		if got := trackAgreement(c.tracks, edition); got != c.want {
+		if got, _ := trackAgreement(c.tracks, edition, false); got != c.want {
 			t.Errorf("%s: %d agree, want %d", c.name, got, c.want)
 		}
 	}
+	// Under the album's own name the titles are enough; the reason a track
+	// did not agree names both sides.
+	edit := []libraryTrack{{Number: 2, Title: "Song (Radio Edit)", LengthMs: 150000}}
+	if n, miss := trackAgreement(edit, edition, false); n != 0 || miss != `"Song (Radio Edit)" runs 2:30 here; MusicBrainz's track 2 is "Song", 3:20` {
+		t.Errorf("by length: %d, %q", n, miss)
+	}
+	if n, _ := trackAgreement(edit, edition, true); n != 1 {
+		t.Errorf("by title alone: %d agree", n)
+	}
+	if _, miss := trackAgreement([]libraryTrack{{Title: "Other", LengthMs: 61000}}, edition, true); miss != `no track of its edition is like "Other" (1:01)` {
+		t.Errorf("unplaced: %q", miss)
+	}
 	if agrees(3, 4) || !agrees(4, 5) || agrees(0, 0) {
 		t.Error("agrees: 80% of the album's tracks, and an album has tracks")
 	}

internal/wanted/match.go

@@ -101,10 +101,14 @@ func tracksToMatch(rows []dbq.ListAlbumTracksToMatchRow) []libraryTrack {
 }
 
 // trackAgreement counts the album's tracks an edition agrees with: the same
-// recording, or a length that fits and a title that agrees. A track is
-// paired by its disc and number first, then by title, so an album missing
-// some tracks still pairs the ones it has.
-func trackAgreement(tracks []libraryTrack, edition []editionTrack) int {
+// recording, or a title that agrees at a length that fits. When the group is
+// called just what the album is called, the titles alone are enough: the
+// lengths are there to tell apart albums whose names only overlap, and a
+// rip's single may be the edit MusicBrainz lists at another length. A track
+// is paired by its disc and number first, then by title, so an album missing
+// some tracks still pairs the ones it has. miss says how the first track
+// that did not agree differs, for the reason a match was refused.
+func trackAgreement(tracks []libraryTrack, edition []editionTrack, titlesEnough bool) (n int, miss string) {
 	byPos := make(map[[2]int]int, len(edition))
 	for i, e := range edition {
 		byPos[[2]int{max(e.Medium, 1), e.Position}] = i
@@ -113,27 +117,47 @@ func trackAgreement(tracks []libraryTrack, edition []editionTrack) int {
 		if t.Recording != "" && strings.EqualFold(t.Recording, e.Recording) {
 			return true
 		}
-		return release.LengthFits(t.LengthMs, e.LengthMs) && release.TitleAgrees(t.Title, e.Title)
+		return release.TitleAgrees(t.Title, e.Title) && (titlesEnough || release.LengthFits(t.LengthMs, e.LengthMs))
 	}
 	used := make([]bool, len(edition))
-	n := 0
 	for _, t := range tracks {
+		at, placed := -1, false
 		if t.Number > 0 {
-			if i, ok := byPos[[2]int{max(t.Disc, 1), t.Number}]; ok && !used[i] && agree(t, edition[i]) {
-				used[i] = true
-				n++
-				continue
+			if i, ok := byPos[[2]int{max(t.Disc, 1), t.Number}]; ok {
+				at = i
+				placed = !used[i] && agree(t, edition[i])
+				if placed {
+					used[i] = true
+				}
 			}
 		}
 		for i, e := range edition {
-			if !used[i] && agree(t, e) {
-				used[i] = true
-				n++
-				break
+			if !placed && !used[i] && agree(t, e) {
+				used[i], placed = true, true
 			}
 		}
+		switch {
+		case placed:
+			n++
+		case miss != "":
+		case at >= 0:
+			e := edition[at]
+			miss = fmt.Sprintf("%q runs %s here; MusicBrainz's track %d is %q, %s",
+				t.Title, minutes(t.LengthMs), e.Position, e.Title, minutes(e.LengthMs))
+		default:
+			miss = fmt.Sprintf("no track of its edition is like %q (%s)", t.Title, minutes(t.LengthMs))
+		}
 	}
-	return n
+	return n, miss
+}
+
+// minutes writes a length as m:ss, or "no length".
+func minutes(ms int) string {
+	if ms <= 0 {
+		return "no length"
+	}
+	sec := (ms + 500) / 1000
+	return fmt.Sprintf("%d:%02d", sec/60, sec%60)
 }
 
 // agrees: enough of the album's tracks agree for the edition to be it.
@@ -173,14 +197,14 @@ func (s *Service) matchAlbum(ctx context.Context, a dbq.ListAlbumsToMatchRow, tr
 	// discography first, then a search.
 	tried := map[string]bool{}
 	var best albumMatch
-	bestN, bestEdition, considered := -1, 0, 0
+	bestN, bestEdition, considered, bestMiss := -1, 0, 0, ""
 	check := func(cands []candidate) error {
 		for _, c := range cands {
 			if tried[c.Group] || len(tried) >= matchCandidates {
 				continue
 			}
 			tried[c.Group] = true
-			n, size, err := s.agreementWith(ctx, c.Group, tracks)
+			n, size, miss, err := s.agreementWith(ctx, c.Group, tracks, sameTitle(c.Title, a.Title))
 			if err != nil {
 				return err
 			}
@@ -189,7 +213,7 @@ func (s *Service) matchAlbum(ctx context.Context, a dbq.ListAlbumsToMatchRow, tr
 			// one; then the edition nearest the album's length.
 			st, bt := sameTitle(c.Title, a.Title), sameTitle(best.Title, a.Title)
 			if n > bestN || (n == bestN && ((st && !bt) || (st == bt && abs(size-len(tracks)) < abs(bestEdition-len(tracks))))) {
-				best, bestN, bestEdition = albumMatch{candidate: c}, n, size
+				best, bestN, bestEdition, bestMiss = albumMatch{candidate: c}, n, size, miss
 			}
 		}
 		return nil
@@ -217,9 +241,15 @@ func (s *Service) matchAlbum(ctx context.Context, a dbq.ListAlbumsToMatchRow, tr
 	if considered == 0 {
 		return albumMatch{Detail: fmt.Sprintf("MusicBrainz has no album called %q by %s.", a.Title, a.ArtistName)}, nil
 	}
-	return albumMatch{Detail: fmt.Sprintf(
-		"MusicBrainz has %d %s called %q by %s, but none has its tracks: the closest, %q, agrees on %d of its %d.",
-		considered, plural(considered, "album", "albums"), a.Title, a.ArtistName, best.Title, max(bestN, 0), len(tracks))}, nil
+	detail := fmt.Sprintf("MusicBrainz has %d %s called %q by %s, but none has its tracks: the closest, %q, agrees on %d of its %d",
+		considered, plural(considered, "album", "albums"), a.Title, a.ArtistName, best.Title, max(bestN, 0), len(tracks))
+	switch {
+	case bestN < 0:
+		detail += " (MusicBrainz lists no edition of it)"
+	case bestMiss != "":
+		detail += ": " + bestMiss
+	}
+	return albumMatch{Detail: detail + "."}, nil
 }
 
 // groupCandidate reads a group the tags name. A group MusicBrainz does not
@@ -296,15 +326,15 @@ func (s *Service) searchCandidates(ctx context.Context, a dbq.ListAlbumsToMatchR
 }
 
 // agreementWith is how many of the album's tracks the group's best edition
-// agrees with, and that edition's length. A group MusicBrainz no longer has
-// agrees with none.
-func (s *Service) agreementWith(ctx context.Context, group string, tracks []libraryTrack) (n, size int, err error) {
+// agrees with, that edition's length, and how it differs. A group
+// MusicBrainz no longer has, or lists no edition of, agrees with none (-1).
+func (s *Service) agreementWith(ctx context.Context, group string, tracks []libraryTrack, titlesEnough bool) (n, size int, miss string, err error) {
 	eds, err := s.cat.Releases(ctx, group)
 	switch {
 	case errors.Is(err, catalogue.ErrNotFound):
-		return -1, 0, nil
+		return -1, 0, "", nil
 	case err != nil:
-		return 0, 0, fmt.Errorf("%w: %v", errMusicBrainzAway, err)
+		return 0, 0, "", fmt.Errorf("%w: %v", errMusicBrainzAway, err)
 	}
 	n = -1
 	for _, e := range eds.Editions {
@@ -313,11 +343,11 @@ func (s *Service) agreementWith(ctx context.Context, group string, tracks []libr
 			edition = append(edition, editionTrack{Medium: int(t.MediumPosition), Position: int(t.Position),
 				Title: t.Title, LengthMs: int(t.LengthMs), Recording: t.RecordingMbid})
 		}
-		if got := trackAgreement(tracks, edition); got > n || (got == n && abs(len(edition)-len(tracks)) < abs(size-len(tracks))) {
-			n, size = got, len(edition)
+		if got, m := trackAgreement(tracks, edition, titlesEnough); got > n || (got == n && abs(len(edition)-len(tracks)) < abs(size-len(tracks))) {
+			n, size, miss = got, len(edition), m
 		}
 	}
-	return n, size, nil
+	return n, size, miss, nil
 }
 
 // creditedArtist is the artist a want is filed under: the library's own