update data store, allow checking if keyring exists, add reset method

keyring.go

@@ -67,6 +67,8 @@ type DataStore interface {
 	// CleanStorage cleanups storage (credentials or key-value).
 	// Error is returned if the vault couldn't be unlocked.
 	CleanStorage(item SecretItem) error
+	// Exists checks if keyring exists in persistent storage.
+	Exists() bool
 	// Save saves the keyring to the persistent storage.
 	Save() error
 	// Destroy removes the keyring from the persistent storage.
@@ -77,6 +79,7 @@ type DataStore interface {
 type Keyring interface {
 	launchr.Service
 	DataStore
+	ResetStorage()
 }
 
 type keyringService struct {
@@ -97,6 +100,11 @@ func (k *keyringService) ServiceInfo() launchr.ServiceInfo {
 	return launchr.ServiceInfo{}
 }
 
+// ResetStorage cleans store for subsequent reload.
+func (k *keyringService) ResetStorage() {
+	k.store = nil
+}
+
 func (k *keyringService) defaultStore() (DataStore, error) {
 	if k.store != nil {
 		return k.store, nil
@@ -167,6 +175,15 @@ func (k *keyringService) CleanStorage(item SecretItem) error {
 	return s.CleanStorage(item)
 }
 
+// Exists checks if keyring exists in persistent storage.
+func (k *keyringService) Exists() bool {
+	s, err := k.defaultStore()
+	if err != nil {
+		return false
+	}
+	return s.Exists()
+}
+
 // Save implements DataStore interface. Uses service default store.
 func (k *keyringService) Save() error {
 	s, err := k.defaultStore()

yaml.go

@@ -175,6 +175,20 @@ func (s *dataStoreYaml) CleanStorage(item SecretItem) error {
 	return nil
 }
 
+// Exists checks if keyring exists in persistent storage.
+func (s *dataStoreYaml) Exists() bool {
+	ageStorage, ok := s.file.(*ageFile)
+	if !ok {
+		panic("impossible type assertion")
+	}
+
+	info, err := os.Stat(ageStorage.file.fname)
+	if os.IsNotExist(err) {
+		return false
+	}
+	return !info.IsDir()
+}
+
 // Save implements DataStore interface.
 func (s *dataStoreYaml) Save() error {
 	err := s.file.Open(os.O_CREATE|os.O_RDWR|os.O_TRUNC, 0600)