Centralize config loading logic

This gets rid of redundant checks and centralizes the logic of loading
the config files so that we don't have to keep doing the same thing in
multiple places.

cmd/syncthing/main.go

@@ -359,10 +359,7 @@ func main() {
 }
 
 func openGUI() {
-	cfg, _, err := loadConfig(locations[locConfigFile])
+	cfg, _ := loadConfig()
-	if err != nil {
-		l.Fatalln("Config:", err)
-	}
 	if cfg.GUI().Enabled {
 		openURL(cfg.GUI().URL())
 	} else {
@@ -433,10 +430,8 @@ func debugFacilities() string {
 }
 
 func checkUpgrade() upgrade.Release {
-	releasesURL := "https://api.github.com/repos/syncthing/syncthing/releases?per_page=30"
+	cfg, _ := loadConfig()
-	if cfg, _, err := loadConfig(locations[locConfigFile]); err == nil {
+	releasesURL := cfg.Options().ReleasesURL
-		releasesURL = cfg.Options().ReleasesURL
-	}
 	release, err := upgrade.LatestRelease(releasesURL, Version)
 	if err != nil {
 		l.Fatalln("Upgrade:", err)
@@ -473,10 +468,7 @@ func performUpgrade(release upgrade.Release) {
 }
 
 func upgradeViaRest() error {
-	cfg, err := config.Load(locations[locConfigFile], protocol.LocalDeviceID)
+	cfg, _ := loadConfig()
-	if err != nil {
-		return err
-	}
 	target := cfg.GUI().URL()
 	r, _ := http.NewRequest("POST", target+"/rest/system/upgrade", nil)
 	r.Header.Set("X-API-Key", cfg.GUI().APIKey())
@@ -573,34 +565,7 @@ func syncthingMain(runtimeOptions RuntimeOptions) {
 		"myID": myID.String(),
 	})
 
-	// Prepare to be able to save configuration
+	cfg := loadOrCreateConfig()
-
-	cfgFile := locations[locConfigFile]
-
-	// Load the configuration file, if it exists.
-	// If it does not, create a template.
-
-	cfg, myName, err := loadConfig(cfgFile)
-	if err != nil {
-		if os.IsNotExist(err) {
-			l.Infoln("No config file; starting with empty defaults")
-			myName, _ = os.Hostname()
-			newCfg := defaultConfig(myName)
-			cfg = config.Wrap(cfgFile, newCfg)
-			cfg.Save()
-			l.Infof("Edit %s to taste or use the GUI\n", cfgFile)
-		} else {
-			l.Fatalln("Loading config:", err)
-		}
-	}
-
-	if cfg.Raw().OriginalVersion != config.CurrentVersion {
-		l.Infoln("Archiving a copy of old config file format")
-		// Archive a copy
-		osutil.Rename(cfgFile, cfgFile+fmt.Sprintf(".v%d", cfg.Raw().OriginalVersion))
-		// Save the new version
-		cfg.Save()
-	}
 
 	if err := checkShortIDs(cfg); err != nil {
 		l.Fatalln("Short device IDs are in conflict. Unlucky!\n  Regenerate the device ID of one of the following:\n  ", err)
@@ -693,7 +658,7 @@ func syncthingMain(runtimeOptions RuntimeOptions) {
 		l.Infoln("Compacting database:", err)
 	}
 
-	m := model.NewModel(cfg, myID, myName, "syncthing", Version, ldb, protectedFiles)
+	m := model.NewModel(cfg, myID, myDeviceName(cfg), "syncthing", Version, ldb, protectedFiles)
 	cfg.Subscribe(m)
 
 	if t := os.Getenv("STDEADLOCKTIMEOUT"); len(t) > 0 {
@@ -886,6 +851,15 @@ func syncthingMain(runtimeOptions RuntimeOptions) {
 	os.Exit(code)
 }
 
+func myDeviceName(cfg *config.Wrapper) string {
+	devices := cfg.Devices()
+	myName := devices[myID].Name
+	if myName == "" {
+		myName, _ = os.Hostname()
+	}
+	return myName
+}
+
 func setupSignalHandling() {
 	// Exit cleanly with "restarting" code on SIGHUP.
 
@@ -924,27 +898,38 @@ func printHashRate() {
 	l.Infof("Single thread hash performance is ~%.*f MB/s", decimals, hashRate)
 }
 
-func loadConfig(cfgFile string) (*config.Wrapper, string, error) {
+func loadConfig() (*config.Wrapper, error) {
-	info, err := os.Stat(cfgFile)
+	cfgFile := locations[locConfigFile]
-	if err != nil {
-		return nil, "", err
-	}
-	if !info.Mode().IsRegular() {
-		return nil, "", errors.New("configuration is not a file")
-	}
-
 	cfg, err := config.Load(cfgFile, myID)
+
 	if err != nil {
-		return nil, "", err
+		l.Infoln("Error loading config file; using defaults for now")
+		myName, _ := os.Hostname()
+		newCfg := defaultConfig(myName)
+		cfg = config.Wrap(cfgFile, newCfg)
 	}
 
-	myCfg := cfg.Devices()[myID]
+	return cfg, err
-	myName := myCfg.Name
+}
-	if myName == "" {
+
-		myName, _ = os.Hostname()
+func loadOrCreateConfig() *config.Wrapper {
+	cfg, err := loadConfig()
+	if os.IsNotExist(err) {
+		cfg.Save()
+		l.Infof("Defaults saved. Edit %s to taste or use the GUI\n", cfg.ConfigPath())
+	} else if err != nil {
+		l.Fatalln("Config:", err)
 	}
 
-	return cfg, myName, nil
+	if cfg.Raw().OriginalVersion != config.CurrentVersion {
+		// Archive previous version and save new one
+		archivePath := cfg.ConfigPath() + fmt.Sprintf(".v%d", cfg.Raw().OriginalVersion)
+		l.Infoln("Archiving a copy of old config file format at:", archivePath)
+		osutil.Rename(cfg.ConfigPath(), archivePath)
+		cfg.Save()
+	}
+
+	return cfg
 }
 
 func startAuditing(mainService *suture.Supervisor) {