centralise special path prefix check

fileutil/fileutil.go

@@ -54,3 +54,8 @@ func First(path ...string) (string, error) {
 	}
 	return "", err
 }
+
+// HasPrefix checks a path has a prefix, making sure to respect path boundaries. So that /aa & /a does not match, but /a/a & /a does.
+func HasPrefix(p, prefix string) bool {
+	return p == prefix || strings.HasPrefix(p, filepath.Clean(prefix)+string(filepath.Separator))
+}

scanner/scanner.go

@@ -20,6 +20,7 @@ import (
 	"github.com/rainycape/unidecode"
 
 	"go.senan.xyz/gonic/db"
+	"go.senan.xyz/gonic/fileutil"
 	"go.senan.xyz/gonic/tags/tagcommon"
 )
 
@@ -721,7 +722,7 @@ func parseMulti(parser tagcommon.Info, setting MultiValueSetting, getMulti func(
 
 func musicDirRelative(musicDirs []string, absPath string) (musicDir, relPath string) {
 	for _, musicDir := range musicDirs {
-		if absPath == musicDir || strings.HasPrefix(absPath, filepath.Clean(musicDir)+string(filepath.Separator)) { // ensure trailing slash for substring check
+		if fileutil.HasPrefix(absPath, musicDir) {
 			relPath, _ = filepath.Rel(musicDir, absPath)
 			return musicDir, relPath
 		}

server/ctrlsubsonic/specidpaths/specidpaths.go

@@ -6,6 +6,7 @@ import (
 	"strings"
 
 	"go.senan.xyz/gonic/db"
+	"go.senan.xyz/gonic/fileutil"
 	"go.senan.xyz/gonic/server/ctrlsubsonic/specid"
 )
 
@@ -54,7 +55,7 @@ func Lookup(dbc *db.DB, musicPaths []string, podcastsPath string, path string) (
 
 	var musicPath string
 	for _, mp := range musicPaths {
-		if strings.HasPrefix(path, filepath.Clean(mp)+string(filepath.Separator) /* ensure trailing */) {
+		if fileutil.HasPrefix(path, mp) {
 			musicPath = mp
 			break
 		}