Adding a node does not require restart; move logic to config package

cmd/syncthing/gui.go

@@ -332,34 +332,7 @@ func restPostConfig(m *model.Model, w http.ResponseWriter, r *http.Request) {
 			}
 		}
 
-		// Figure out if any changes require a restart
+		// Start or stop usage reporting as appropriate
-
-		if len(cfg.Repositories) != len(newCfg.Repositories) {
-			configInSync = false
-		} else {
-			om := cfg.RepoMap()
-			nm := newCfg.RepoMap()
-			for id := range om {
-				if !reflect.DeepEqual(om[id], nm[id]) {
-					configInSync = false
-					break
-				}
-			}
-		}
-
-		if len(cfg.Nodes) != len(newCfg.Nodes) {
-			configInSync = false
-		} else {
-			om := cfg.NodeMap()
-			nm := newCfg.NodeMap()
-			for k := range om {
-				if _, ok := nm[k]; !ok {
-					// A node was removed and another added
-					configInSync = false
-					break
-				}
-			}
-		}
 
 		if newCfg.Options.URAccepted > cfg.Options.URAccepted {
 			// UR was enabled
@@ -375,12 +348,9 @@ func restPostConfig(m *model.Model, w http.ResponseWriter, r *http.Request) {
 			stopUsageReporting()
 		}
 
-		if !reflect.DeepEqual(cfg.Options, newCfg.Options) || !reflect.DeepEqual(cfg.GUI, newCfg.GUI) {
-			configInSync = false
-		}
-
 		// Activate and save
 
+		configInSync = !config.ChangeRequiresRestart(cfg, newCfg)
 		newCfg.Location = cfg.Location
 		newCfg.Save()
 		cfg = newCfg

config/config.go

@@ -423,6 +423,39 @@ func Load(location string, myID protocol.NodeID) (Configuration, error) {
 	return cfg, err
 }
 
+// ChangeRequiresRestart returns true if updating the configuration requires a
+// complete restart.
+func ChangeRequiresRestart(from, to Configuration) bool {
+	// Adding, removing or changing repos requires restart
+	if len(from.Repositories) != len(to.Repositories) {
+		return true
+	}
+	fromRepos := from.RepoMap()
+	toRepos := to.RepoMap()
+	for id := range fromRepos {
+		if !reflect.DeepEqual(fromRepos[id], toRepos[id]) {
+			return true
+		}
+	}
+
+	// Removing a node requires a restart. Adding one does not. Changing
+	// address or name does not.
+	fromNodes := from.NodeMap()
+	toNodes := to.NodeMap()
+	for nodeID := range fromNodes {
+		if _, ok := toNodes[nodeID]; !ok {
+			return true
+		}
+	}
+
+	// All of the generic options require restart
+	if !reflect.DeepEqual(from.Options, to.Options) || !reflect.DeepEqual(from.GUI, to.GUI) {
+		return true
+	}
+
+	return false
+}
+
 func convertV3V4(cfg *Configuration) {
 	// In previous versions, rescan interval was common for each repository.
 	// From now, it can be set independently. We have to make sure, that after upgrade