lib/model: Discard download progress upon receiving an index update (fixes #2993)

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3023

lib/model/devicedownloadstate.go

@@ -97,6 +97,9 @@ type deviceDownloadState struct {
 // Update updates internal state of what has been downloaded into the temporary
 // files by the remote device for this specific folder.
 func (t *deviceDownloadState) Update(folder string, updates []protocol.FileDownloadProgressUpdate) {
+	if t == nil {
+		return
+	}
 	t.mut.RLock()
 	f, ok := t.folders[folder]
 	t.mut.RUnlock()

lib/model/model.go

@@ -556,6 +556,10 @@ func (m *Model) Index(deviceID protocol.DeviceID, folder string, fs []protocol.F
 		l.Fatalf("Index for nonexistant folder %q", folder)
 	}
 
+	m.pmut.RLock()
+	m.deviceDownloads[deviceID].Update(folder, makeForgetUpdate(fs))
+	m.pmut.RUnlock()
+
 	fs = filterIndex(folder, fs, cfg.IgnoreDelete, ignores)
 	files.Replace(deviceID, fs)
 
@@ -593,6 +597,10 @@ func (m *Model) IndexUpdate(deviceID protocol.DeviceID, folder string, fs []prot
 		l.Fatalf("IndexUpdate for nonexistant folder %q", folder)
 	}
 
+	m.pmut.RLock()
+	m.deviceDownloads[deviceID].Update(folder, makeForgetUpdate(fs))
+	m.pmut.RUnlock()
+
 	fs = filterIndex(folder, fs, cfg.IgnoreDelete, ignores)
 	files.Update(deviceID, fs)
 
@@ -2216,3 +2224,20 @@ next:
 
 	return cleaned
 }
+
+// makeForgetUpdate takes an index update and constructs a download progress update
+// causing to forget any progress for files which we've just been sent.
+func makeForgetUpdate(files []protocol.FileInfo) []protocol.FileDownloadProgressUpdate {
+	updates := make([]protocol.FileDownloadProgressUpdate, 0, len(files))
+	for _, file := range files {
+		if file.IsSymlink() || file.IsDirectory() || file.IsDeleted() {
+			continue
+		}
+		updates = append(updates, protocol.FileDownloadProgressUpdate{
+			Name:       file.Name,
+			Version:    file.Version,
+			UpdateType: protocol.UpdateTypeForget,
+		})
+	}
+	return updates
+}