Import tracks in QThread

Allows progress messages to be sent
Fixes #164

app/musicmuster.py

@@ -1,6 +1,7 @@
 #!/usr/bin/env python
 
 from log import log
+from os.path import basename
 import argparse
 import stackprinter                         # type: ignore
 import subprocess
@@ -20,8 +21,10 @@ from PyQt5.QtCore import (
     pyqtSignal,
     QDate,
     QEvent,
+    QObject,
     Qt,
     QSize,
+    QThread,
     QTime,
     QTimer,
 )
@@ -209,6 +212,42 @@ class PlaylistTrack:
                 self.start_time + timedelta(milliseconds=self.duration))
 
 
+class ImportTrack(QObject):
+    import_error = pyqtSignal(str)
+    importing = pyqtSignal(str)
+    finished = pyqtSignal(PlaylistTab)
+
+    def __init__(self, playlist: PlaylistTab, filenames: list) -> None:
+        super().__init__()
+        self.filenames = filenames
+        self.playlist = playlist
+
+    def run(self):
+        """
+        Create track objects from passed files and add to visible playlist
+        """
+
+        with Session() as session:
+            for fname in self.filenames:
+                self.importing.emit(f"Importing {basename(fname)}")
+                try:
+                    track = Tracks(session, fname)
+                except ValueError:
+                    self.import_error.emit(basename(fname))
+                    continue
+                helpers.set_track_metadata(session, track)
+                helpers.normalise_track(track.path)
+                self.playlist.insert_track(session, track)
+                # We're importing potentially multiple tracks in a loop.
+                # If there's an error adding the track to the Tracks
+                # table, the session will rollback, thus losing any
+                # previous additions in this loop. So, commit now to
+                # lock in what we've just done.
+                session.commit()
+            self.playlist.save_playlist(session)
+            self.finished.emit(self.playlist)
+
+
 class Window(QMainWindow, Ui_MainWindow):
     def __init__(self, parent=None, *args, **kwargs) -> None:
         super().__init__(*args, **kwargs)
@@ -806,7 +845,7 @@ class Window(QMainWindow, Ui_MainWindow):
             for fname in dlg.selectedFiles():
                 txt = ""
                 tags = helpers.get_tags(fname)
-                new_tracks.append((fname, tags))
+                new_tracks.append(fname)
                 title = tags['title']
                 artist = tags['artist']
                 count = 0
@@ -834,26 +873,32 @@ class Window(QMainWindow, Ui_MainWindow):
                         return
 
         # Import in separate thread
-        thread = threading.Thread(target=self._import_tracks,
+        self.import_thread = QThread()
-                                  args=(new_tracks,))
+        self.worker = ImportTrack(self.visible_playlist_tab(), new_tracks)
-        thread.start()
+        self.worker.moveToThread(self.import_thread)
+        self.import_thread.started.connect(self.worker.run)
+        self.worker.finished.connect(self.import_thread.quit)
+        self.worker.finished.connect(self.worker.deleteLater)
+        self.import_thread.finished.connect(self.import_thread.deleteLater)
+        self.worker.import_error.connect(
+            lambda msg: helpers.show_warning(
+                "Import error", "Error importing " + msg
+            )
+        )
+        self.worker.importing.connect(
+            lambda msg: self.statusbar.showMessage("Importing " + msg, 5000)
+        )
+        self.worker.finished.connect(self.import_complete)
+        self.import_thread.start()
 
-    def _import_tracks(self, tracks: list):
+    def import_complete(self, playlist_tab: PlaylistTab):
         """
-        Create track objects from passed files and add to visible playlist
+        Called by thread when track import complete
         """
 
+        self.statusbar.showMessage("Imports complete")
         with Session() as session:
-            for (fname, tags) in tracks:
+            playlist_tab.update_display(session)
-                try:
-                    track = Tracks(session, fname)
-                except ValueError:
-                    # Error adding track to database
-                    continue
-                helpers.set_track_metadata(session, track)
-                helpers.normalise_track(track.path)
-                self.visible_playlist_tab().insert_track(session, track)
-            self.visible_playlist_tab().save_playlist(session)
 
     def insert_header(self) -> None:
         """Show dialog box to enter header text and add to playlist"""