Only update temporary metadata when set

Fixes #507

src/collection/collectionplaylistitem.h

@@ -40,6 +40,7 @@ class CollectionPlaylistItem : public PlaylistItem {
   void Reload() override;
 
   Song Metadata() const override;
+  Song OriginalMetadata() const override { return song_; }
   void SetMetadata(const Song &song) { song_ = song; }
 
   QUrl Url() const override;

src/internet/internetplaylistitem.h

@@ -40,6 +40,7 @@ class InternetPlaylistItem : public PlaylistItem {
 
   bool InitFromQuery(const SqlRow &query) override;
   Song Metadata() const override;
+  Song OriginalMetadata() const override { return metadata_; }
   QUrl Url() const override;
   void SetArtManual(const QUrl &cover_url) override;
 

src/playlist/playlist.cpp

@@ -406,16 +406,8 @@ void Playlist::ItemReloadComplete(const QPersistentModelIndex &index) {
   if (index.isValid()) {
 
     PlaylistItemPtr item = item_at(index.row());
-    if (item) {
-
-      // Update temporary metadata for songs that are not in the collection.
-      // Songs that are in the collection is updated through the collection watcher/backend in playlist manager.
-      if (item->Metadata().source() != Song::Source_Collection) {
-        SongPlaylistItem *song_item = static_cast<SongPlaylistItem*>(item.get());
-        if (song_item) {
-          song_item->UpdateTemporaryMetadata(song_item->DatabaseSongMetadata());
-        }
-      }
+    if (item && item->HasTemporaryMetadata()) {  // Update temporary metadata.
+      item->UpdateTemporaryMetadata(item->OriginalMetadata());
     }
 
     emit dataChanged(index, index);

src/playlist/playlistitem.cpp

@@ -76,6 +76,8 @@ void PlaylistItem::SetTemporaryMetadata(const Song &metadata) {
 
 void PlaylistItem::UpdateTemporaryMetadata(const Song &metadata) {
 
+  if (!temp_metadata_.is_valid()) return;
+
   Song old_metadata = temp_metadata_;
   temp_metadata_ = metadata;
 

src/playlist/playlistitem.h

@@ -73,6 +73,7 @@ class PlaylistItem : public std::enable_shared_from_this<PlaylistItem> {
   QFuture<void> BackgroundReload();
 
   virtual Song Metadata() const = 0;
+  virtual Song OriginalMetadata() const = 0;
   virtual QUrl Url() const = 0;
 
   void SetTemporaryMetadata(const Song &metadata);

src/playlist/playlistmanager.cpp

@@ -480,7 +480,7 @@ void PlaylistManager::SongsDiscovered(const SongList &songs) {
       for (PlaylistItemPtr item : items) {
         if (item->Metadata().directory_id() != song.directory_id()) continue;
         static_cast<CollectionPlaylistItem*>(item.get())->SetMetadata(song);
-        item->UpdateTemporaryMetadata(song);
+        if (item->HasTemporaryMetadata()) item->UpdateTemporaryMetadata(song);
         data.p->ItemChanged(item);
       }
     }

src/playlist/songplaylistitem.h

@@ -41,12 +41,15 @@ class SongPlaylistItem : public PlaylistItem {
   void Reload() override;
 
   Song Metadata() const override;
+  Song OriginalMetadata() const override { return song_; }
 
   QUrl Url() const override;
 
-  Song DatabaseSongMetadata() const override { return song_; }
   void SetArtManual(const QUrl &cover_url) override;
 
+ protected:
+  Song DatabaseSongMetadata() const override { return song_; }
+
  private:
   Song song_;
 };