HasCompilations() implementation local to the LibraryModel

Instead of relying on the backend to provide us with the information
of whether there are compilations in the whole of the library, we instead
look into the query we are currently working with for compilations. This
way we can be as granular as we want in the future.

This also means we now have to add the Various artists node at the time we
do the query with RunQuery() instead at BeginReset().

src/library/librarybackend.cpp

@@ -628,18 +628,6 @@ SongList LibraryBackend::GetSongsByUrl(const QUrl& url) {
   return songlist;
 }
 
-bool LibraryBackend::HasCompilations(const QueryOptions& opt) {
-  LibraryQuery query(opt);
-  query.SetColumnSpec("%songs_table.ROWID");
-  query.AddCompilationRequirement(true);
-  query.SetLimit(1);
-
-  QMutexLocker l(db_->Mutex());
-  if (!ExecQuery(&query)) return false;
-
-  return query.Next();
-}
-
 LibraryBackend::AlbumList LibraryBackend::GetCompilationAlbums(const QueryOptions& opt) {
   return GetAlbums(QString(), true, opt);
 }

src/library/librarybackend.h

@@ -74,7 +74,6 @@ class LibraryBackendInterface : public QObject {
   virtual SongList GetSongs(
       const QString& artist, const QString& album, const QueryOptions& opt = QueryOptions()) = 0;
 
-  virtual bool HasCompilations(const QueryOptions& opt = QueryOptions()) = 0;
   virtual SongList GetCompilationSongs(const QString& album, const QueryOptions& opt = QueryOptions()) = 0;
 
   virtual AlbumList GetAllAlbums(const QueryOptions& opt = QueryOptions()) = 0;
@@ -132,7 +131,6 @@ class LibraryBackend : public LibraryBackendInterface {
   SongList GetSongsByAlbum(const QString& album, const QueryOptions& opt = QueryOptions());
   SongList GetSongs(const QString& artist, const QString& album, const QueryOptions& opt = QueryOptions());
 
-  bool HasCompilations(const QueryOptions& opt = QueryOptions());
   SongList GetCompilationSongs(const QString& album, const QueryOptions& opt = QueryOptions());
 
   AlbumList GetAllAlbums(const QueryOptions& opt = QueryOptions());

src/library/librarymodel.cpp

@@ -554,6 +554,17 @@ QVariant LibraryModel::data(const LibraryItem* item, int role) const {
   return QVariant();
 }
 
+bool LibraryModel::HasCompilations(const LibraryQuery query) {
+  LibraryQuery q = query;
+  q.AddCompilationRequirement(true);
+  q.SetLimit(1);
+
+  QMutexLocker l(backend_->db()->Mutex());
+  if (!backend_->ExecQuery(&q)) return false;
+
+  return q.Next();
+}
+
 SqlRowList LibraryModel::RunQuery(LibraryItem* parent, bool signal) {
   // Information about what we want the children to be
   int child_level = parent == root_ ? 0 : parent->container_level + 1;
@@ -573,6 +584,10 @@ SqlRowList LibraryModel::RunQuery(LibraryItem* parent, bool signal) {
 
   // Top-level artists is special - we don't want compilation albums appearing
   if (child_level == 0 && IsArtistGroupBy(child_type)) {
+    // Various artists?
+    if (show_various_artists_ && HasCompilations(q))
+      CreateCompilationArtistNode(signal, parent);
+
     q.AddCompilationRequirement(false);
   }
 
@@ -661,13 +676,6 @@ void LibraryModel::BeginReset() {
   root_ = new LibraryItem(this);
   root_->lazy_loaded = false;
 
-  if (show_various_artists_) {
-    // Various artists?
-    if (IsArtistGroupBy(group_by_[0]) &&
-        backend_->HasCompilations(query_options_))
-      CreateCompilationArtistNode(false, root_);
-  }
-
   // Smart playlists?
   if (show_smart_playlists_ && query_options_.filter().isEmpty())
     CreateSmartPlaylists();

src/library/librarymodel.h

@@ -189,6 +189,8 @@ class LibraryModel : public SimpleTreeModel<LibraryItem> {
   SqlRowList RunQuery(LibraryItem* parent, bool signal);
   void PostQuery(LibraryItem* parent, SqlRowList rows, bool signal);
 
+  bool HasCompilations(const LibraryQuery query);
+
   void BeginReset();
 
   // Functions for working with queries and creating items.

tests/mock_librarybackend.h

@@ -41,7 +41,6 @@ class MockLibraryBackend : public LibraryBackendInterface {
   MOCK_METHOD1(GetAllArtistsWithAlbums, QStringList(const QueryOptions&));
   MOCK_METHOD3(GetSongs, SongList(const QString&, const QString&, const QueryOptions&));
 
-  MOCK_METHOD1(HasCompilations, bool(const QueryOptions&));
   MOCK_METHOD2(GetCompilationSongs, SongList(const QString&, const QueryOptions&));
 
   MOCK_METHOD1(GetAllAlbums, AlbumList(const QueryOptions&));