feat: error type for not finding basic auth creds and export config path

registry/remote/auth/client.go

@@ -31,6 +31,8 @@
 	"oras.land/oras-go/v2/registry/remote/retry"
 )
 
+var ErrBasicCredentialNotFound = errors.New("basic credential not found")
+
 // DefaultClient is the default auth-decorated client.
 var DefaultClient = &Client{
 	Client: retry.DefaultClient,
@@ -280,7 +282,7 @@
 		return "", fmt.Errorf("failed to resolve credential: %w", err)
 	}
 	if cred == EmptyCredential {
-		return "", errors.New("credential required for basic auth")
+		return "", ErrBasicCredentialNotFound
 	}
 	if cred.Username == "" || cred.Password == "" {
 		return "", errors.New("missing username or password for basic auth")

registry/remote/credentials/store.go

@@ -51,6 +51,7 @@ type Store interface {
 // in the config file.
 type DynamicStore struct {
 	config             *config.Config
+	configPath         string
 	options            StoreOptions
 	detectedCredsStore string
 	setCredsStoreOnce  sync.Once
@@ -100,8 +101,9 @@ func NewStore(configPath string, opts StoreOptions) (*DynamicStore, error) {
 		return nil, err
 	}
 	ds := &DynamicStore{
-		config:  cfg,
-		options: opts,
+		config:     cfg,
+		configPath: configPath,
+		options:    opts,
 	}
 	if opts.DetectDefaultNativeStore && !cfg.IsAuthConfigured() {
 		// no authentication configured, detect the default credentials store
@@ -167,6 +169,14 @@ func (ds *DynamicStore) IsAuthConfigured() bool {
 	return ds.config.IsAuthConfigured()
 }
 
+// ConfigPath returns the path to the config file.
+func (ds *DynamicStore) ConfigPath() (string, error) {
+	if ds.config == nil {
+		return "", fmt.Errorf("config is not loaded")
+	}
+	return ds.configPath, nil
+}
+
 // getHelperSuffix returns the credential helper suffix for the given server
 // address.
 func (ds *DynamicStore) getHelperSuffix(serverAddress string) string {

registry/remote/credentials/store_test.go

@@ -611,6 +611,29 @@ func Test_DynamicStore_getHelperSuffix(t *testing.T) {
 		})
 	}
 }
+func Test_DynamicStore_GetConfigPath(t *testing.T) {
+	path := "../../testdata/credsStore_config.json"
+	var err error
+	store, err := NewStore(path, StoreOptions{})
+	if err != nil {
+		t.Fatal("NewFileStore() error =", err)
+	}
+	got, err := store.ConfigPath()
+	if err != nil {
+		t.Errorf("Config.GetPath() error = %v", err)
+	}
+	if got != path {
+		t.Errorf("Config.GetPath() = %v, want %v", got, path)
+	}
+}
+
+func Test_DynamicStore_Path_nil(t *testing.T) {
+	var store DynamicStore
+	_, err := store.ConfigPath()
+	if err == nil {
+		t.Error("expecting error, got nil")
+	}
+}
 
 func Test_DynamicStore_getStore_nativeStore(t *testing.T) {
 	tests := []struct {