gui, lib/model: Add new state FolderPreparingSync (fixes #6027) (#6028)

gui/default/index.html

@@ -323,6 +323,10 @@
                     <span class="visible-xs" aria-label="{{'Scanning' | translate}}"><i class="fas fa-fw fa-search"></i></span>
                   </span>
                   <span ng-switch-when="idle"><span class="hidden-xs" translate>Up to Date</span><span class="visible-xs" aria-label="{{'Up to Date' | translate}}"><i class="fas fa-fw fa-check"></i></span></span>
+                  <span ng-switch-when="sync-preparing">
+                    <span class="hidden-xs" translate>Preparing to Sync</span>
+                    <span class="visible-xs" aria-label="{{'Preparing to Sync' | translate}}"><i class="fas fa-fw fa-hourglass-half"></i></span>
+                  </span>
                   <span ng-switch-when="syncing">
                     <span class="hidden-xs" translate>Syncing</span>
                     <span>({{syncPercentage(folder.id) | percent}}, {{model[folder.id].needBytes | binary}}B)</span>

gui/default/syncthing/core/syncthingController.js

@@ -803,7 +803,7 @@ angular.module('syncthing.core')
             if (status == 'paused') {
                 return 'default';
             }
-            if (status === 'syncing' || status === 'scanning') {
+            if (status === 'syncing' || status === 'sync-preparing' || status === 'scanning') {
                 return 'primary';
             }
             if (status === 'unknown') {
@@ -968,6 +968,7 @@ angular.module('syncthing.core')
             for (var i = 0; i < folderListCache.length; i++) {
                 var status = $scope.folderStatus(folderListCache[i]);
                 switch (status) {
+                    case 'sync-preparing':
                     case 'syncing':
                         syncCount++;
                         break;

lib/model/folder_sendrecv.go

@@ -176,7 +176,6 @@ func (f *sendReceiveFolder) pull() bool {
 
 	l.Debugf("%v pulling", f)
 
-	f.setState(FolderSyncing)
 	f.clearPullErrors()
 
 	scanChan := make(chan string)
@@ -194,6 +193,10 @@ func (f *sendReceiveFolder) pull() bool {
 		default:
 		}
 
+		// Needs to be set on every loop, as the puller might have set
+		// it to FolderSyncing during the last iteration.
+		f.setState(FolderSyncPreparing)
+
 		changed := f.pullerIteration(scanChan)
 
 		l.Debugln(f, "changed", changed, "on try", tries+1)
@@ -1396,6 +1399,8 @@ func (f *sendReceiveFolder) pullerRoutine(in <-chan pullBlockState, out chan<- *
 			continue
 		}
 
+		f.setState(FolderSyncing) // Does nothing if already FolderSyncing
+
 		// The requestLimiter limits how many pending block requests we have
 		// ongoing at any given time, based on the size of the blocks
 		// themselves.

lib/model/folderstate.go

@@ -19,6 +19,7 @@ const (
 	FolderIdle folderState = iota
 	FolderScanning
 	FolderScanWaiting
+	FolderSyncPreparing
 	FolderSyncing
 	FolderError
 )
@@ -31,6 +32,8 @@ func (s folderState) String() string {
 		return "scanning"
 	case FolderScanWaiting:
 		return "scan-waiting"
+	case FolderSyncPreparing:
+		return "sync-preparing"
 	case FolderSyncing:
 		return "syncing"
 	case FolderError:
@@ -65,29 +68,32 @@ func (s *stateTracker) setState(newState folderState) {
 	}
 
 	s.mut.Lock()
-	if newState != s.current {
-		/* This should hold later...
-		if s.current != FolderIdle && (newState == FolderScanning || newState == FolderSyncing) {
-			panic("illegal state transition " + s.current.String() + " -> " + newState.String())
-		}
-		*/
-
-		eventData := map[string]interface{}{
-			"folder": s.folderID,
-			"to":     newState.String(),
-			"from":   s.current.String(),
-		}
-
-		if !s.changed.IsZero() {
-			eventData["duration"] = time.Since(s.changed).Seconds()
-		}
-
-		s.current = newState
-		s.changed = time.Now()
-
-		s.evLogger.Log(events.StateChanged, eventData)
+	defer s.mut.Unlock()
+
+	if newState == s.current {
+		return
 	}
-	s.mut.Unlock()
+
+	/* This should hold later...
+	if s.current != FolderIdle && (newState == FolderScanning || newState == FolderSyncing) {
+		panic("illegal state transition " + s.current.String() + " -> " + newState.String())
+	}
+	*/
+
+	eventData := map[string]interface{}{
+		"folder": s.folderID,
+		"to":     newState.String(),
+		"from":   s.current.String(),
+	}
+
+	if !s.changed.IsZero() {
+		eventData["duration"] = time.Since(s.changed).Seconds()
+	}
+
+	s.current = newState
+	s.changed = time.Now()
+
+	s.evLogger.Log(events.StateChanged, eventData)
 }
 
 // getState returns the current state, the time when it last changed, and the