MetadataParser: Properly handle playlist rescan

src/MediaLibrary.cpp

@@ -1292,7 +1292,7 @@ void MediaLibrary::forceRescan()
         Show::deleteAll( this );
         VideoTrack::deleteAll( this );
         AudioTrack::deleteAll( this );
-        Playlist::deleteAllExternal( this );
+        Playlist::clearExternalPlaylistContent( this );
         parser::Task::resetParsing( this );
         clearCache();
         Artist::createDefaultArtists( getConn() );

src/Playlist.cpp

@@ -278,10 +278,15 @@ Query<IPlaylist> Playlist::listAll( MediaLibraryPtr ml, SortingCriteria sort, bo
     return make_query<Playlist, IPlaylist>( ml, "*", req );
 }
 
-void Playlist::deleteAllExternal(MediaLibraryPtr ml)
+void Playlist::clearExternalPlaylistContent(MediaLibraryPtr ml)
 {
-    const std::string req = "DELETE FROM " + policy::PlaylistTable::Name +
-            " WHERE file_id IS NOT NULL";
+    // We can't delete all external playlist as such, since this would cause the
+    // deletion of the associated task through the Task.playlist_id Playlist.id_playlist
+    // foreign key, and therefor they wouldn't be rescanned.
+    // Instead, flush the playlist content.
+    const std::string req = "DELETE FROM PlaylistMediaRelation WHERE playlist_id IN ("
+            "SELECT id_playlist FROM " + policy::PlaylistTable::Name + " WHERE "
+            "file_id IS NOT NULL)";
     sqlite::Tools::executeDelete( ml->getConn(), req );
 }
 

src/Playlist.h

@@ -78,7 +78,7 @@ public:
      *                          that were parsed from playlist files.
      * Playlist manually added by the user are untouched
      */
-    static void deleteAllExternal( MediaLibraryPtr ml );
+    static void clearExternalPlaylistContent( MediaLibraryPtr ml );
 
 private:
     static std::string sortRequest( SortingCriteria sort, bool desc );

src/metadata_services/MetadataParser.cpp

@@ -235,28 +235,54 @@ parser::Task::Status MetadataParser::run( parser::Task& task )
 
 bool MetadataParser::addPlaylistMedias( parser::Task& task ) const
 {
-    auto t = m_ml->getConn()->newTransaction();
     const auto& mrl = task.item().mrl();
     LOG_INFO( "Try to import ", mrl, " as a playlist" );
-    auto playlistName = task.item().meta( parser::Task::Item::Metadata::Title );
-    if ( playlistName.empty() == true )
-        playlistName = utils::url::decode( utils::file::fileName( mrl ) );
-    auto playlistPtr = Playlist::create( m_ml, playlistName );
-    if ( playlistPtr == nullptr )
-    {
-        LOG_ERROR( "Failed to create playlist ", mrl, " to the media library" );
-        return false;
+    std::shared_ptr<Playlist> playlistPtr;
+    if ( task.item().file() != nullptr )
+    {
+        // We are most likely re-scanning a file representing a playlist.
+        // If a task has a file, it means the playlist & the associated file have
+        // been created.
+        std::string req = "SELECT * FROM " + policy::PlaylistTable::Name +
+                " WHERE file_id = ?";
+        playlistPtr = Playlist::fetch( m_ml, req, task.item().file()->id() );
+        if ( playlistPtr == nullptr )
+        {
+            // The playlist had to be created, something is very wrong, give up
+            // FIXME: Check that the task will be deleted.
+            assert( false );
+            return false;
+        }
     }
-    auto file = playlistPtr->addFile( *task.item().fileFs(),
-                                      task.item().parentFolder()->id(),
-                                      task.item().parentFolderFs()->device()->isRemovable() );
-    if ( file == nullptr )
+    else
     {
-        LOG_ERROR( "Failed to add playlist file ", mrl );
-        return false;
+        auto playlistName = task.item().meta( parser::Task::Item::Metadata::Title );
+        if ( playlistName.empty() == true )
+            playlistName = utils::url::decode( utils::file::fileName( mrl ) );
+        auto t = m_ml->getConn()->newTransaction();
+        playlistPtr = Playlist::create( m_ml, playlistName );
+        if ( playlistPtr == nullptr )
+        {
+            LOG_ERROR( "Failed to create playlist ", mrl, " to the media library" );
+            return false;
+        }
+
+        auto file = playlistPtr->addFile( *task.item().fileFs(),
+                                          task.item().parentFolder()->id(),
+                                          task.item().parentFolderFs()->device()->isRemovable() );
+        if ( file == nullptr )
+        {
+            LOG_ERROR( "Failed to add playlist file ", mrl );
+            return false;
+        }
+        task.item().setFile( std::move( file ) );
+        t->commit();
     }
-    task.item().setFile( std::move( file ) );
-    t->commit();
+    // Now regardless of if the playlist is re-scanned or discovered from the
+    // first time, just schedule all members for insertion. media & files will
+    // be recreated if need be, and appropriate entries in PlaylistMediaRelation
+    // table will be recreated to link things together.
+
     auto subitems = task.item().subItems();
     for ( const auto& subItem : subitems ) // FIXME: Interrupt loop if paused
         addPlaylistElement( task, playlistPtr, subItem );