Allow cover search only using either artist, album or title

src/covermanager/albumcoverfetchersearch.cpp

@@ -98,8 +98,8 @@ void AlbumCoverFetcherSearch::Start(CoverProviders *cover_providers) {
       continue;
     }
 
-    // If album is missing, check if we can still use this provider by searching using artist + title.
-    if (!provider->allow_missing_album() && request_.album.isEmpty()) {
+    // If artist and album is missing, check if we can still use this provider by searching using title.
+    if (!provider->allow_missing_album() && request_.artist.isEmpty() && request_.album.isEmpty()) {
       continue;
     }
 

src/covermanager/deezercoverprovider.cpp

@@ -69,15 +69,21 @@ bool DeezerCoverProvider::StartSearch(const QString &artist, const QString &albu
   typedef QPair<QString, QString> Param;
   typedef QList<Param> Params;
 
+  if (artist.isEmpty() && album.isEmpty() && title.isEmpty()) return false;
+
   QString resource;
-  QString query;
-  if (album.isEmpty()) {
+  QString query = artist;
+  if (album.isEmpty() && !title.isEmpty()) {
     resource = "search/track";
-    query = artist + " " + title;
+    if (!query.isEmpty()) query.append(" ");
+    query.append(title);
   }
   else {
     resource = "search/album";
-    query = artist + " " + album;
+    if (!album.isEmpty()) {
+      if (!query.isEmpty()) query.append(" ");
+      query.append(album);
+    }
   }
 
   const Params params = Params() << Param("output", "json")

src/covermanager/discogscoverprovider.cpp

@@ -91,6 +91,8 @@ bool DiscogsCoverProvider::StartSearch(const QString &artist, const QString &alb
 
   Q_UNUSED(title);
 
+  if (artist.isEmpty() || album.isEmpty()) return false;
+
   std::shared_ptr<DiscogsCoverSearchContext> search = std::make_shared<DiscogsCoverSearchContext>(id, artist, album);
 
   requests_search_.insert(search->id, search);

src/covermanager/lastfmcoverprovider.cpp

@@ -71,18 +71,24 @@ bool LastFmCoverProvider::StartSearch(const QString &artist, const QString &albu
   typedef QPair<QString, QString> Param;
   typedef QList<Param> ParamList;
 
+  if (artist.isEmpty() && album.isEmpty() && title.isEmpty()) return false;
+
   QString method;
   QString type;
-  QString query;
-  if (album.isEmpty()) {
+  QString query = artist;
+  if (album.isEmpty() && !title.isEmpty()) {
     method = "track.search";
     type = "track";
-    query = artist + " " + title;
+    if (!query.isEmpty()) query.append(" ");
+    query.append(title);
   }
   else {
     method = "album.search";
     type = "album";
-    query = artist + " " + album;
+    if (!album.isEmpty()) {
+      if (!query.isEmpty()) query.append(" ");
+      query.append(album);
+    }
   }
 
   ParamList params = ParamList() << Param("api_key", kApiKey)

src/covermanager/musicbrainzcoverprovider.cpp

@@ -74,6 +74,8 @@ bool MusicbrainzCoverProvider::StartSearch(const QString &artist, const QString
 
   Q_UNUSED(title);
 
+  if (artist.isEmpty() || album.isEmpty()) return false;
+
   SearchRequest request(id, artist, album);
   queue_search_requests_ << request;
 

src/covermanager/qobuzcoverprovider.cpp

@@ -297,12 +297,8 @@ bool QobuzCoverProvider::StartSearch(const QString &artist, const QString &album
 
   if (artist.isEmpty() && album.isEmpty() && title.isEmpty()) return false;
 
-  QString query;
-  if (!artist.isEmpty()) {
-    query.append(artist);
-  }
-
   QString resource;
+  QString query = artist;
   if (album.isEmpty() && !title.isEmpty()) {
     resource = "track/search";
     if (!query.isEmpty()) query.append(" ");

src/covermanager/spotifycoverprovider.cpp

@@ -356,18 +356,24 @@ bool SpotifyCoverProvider::StartSearch(const QString &artist, const QString &alb
 
   if (access_token_.isEmpty()) return false;
 
+  if (artist.isEmpty() && album.isEmpty() && title.isEmpty()) return false;
+
   QString type;
-  QString query;
   QString extract;
-  if (album.isEmpty()) {
+  QString query = artist;
+  if (album.isEmpty() && !title.isEmpty()) {
     type = "track";
-    query = artist + " " + title;
     extract = "tracks";
+    if (!query.isEmpty()) query.append(" ");
+    query.append(title);
   }
   else {
     type = "album";
-    query = artist + " " + album;
     extract = "albums";
+    if (!album.isEmpty()) {
+      if (!query.isEmpty()) query.append(" ");
+      query.append(album);
+    }
   }
 
   ParamList params = ParamList() << Param("q", query)

src/covermanager/tidalcoverprovider.cpp

@@ -77,15 +77,21 @@ bool TidalCoverProvider::StartSearch(const QString &artist, const QString &album
 
   if (!service_ || !service_->authenticated()) return false;
 
+  if (artist.isEmpty() && album.isEmpty() && title.isEmpty()) return false;
+
   QString resource;
-  QString query;
-  if (album.isEmpty()) {
+  QString query = artist;
+  if (album.isEmpty() && !title.isEmpty()) {
     resource = "search/tracks";
-    query = artist + " " + title;
+    if (!query.isEmpty()) query.append(" ");
+    query.append(title);
   }
   else {
     resource = "search/albums";
-    query = artist + " " + album;
+    if (!album.isEmpty()) {
+      if (!query.isEmpty()) query.append(" ");
+      query.append(album);
+    }
   }
 
   ParamList params = ParamList() << Param("query", query)