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

registry/remote/auth/client.go

@@ -31,6 +31,10 @@
 	"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 +284,7 @@
 		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/internal/config/config.go

@@ -155,6 +155,14 @@ func Load(configPath string) (*Config, error) {
 	return cfg, nil
 }
 
+// Path returns the path to the config file.
+func (cfg *Config) Path() (string, error) {
+	if cfg == nil {
+		return "", errors.New("config file is nil")
+	}
+	return cfg.path, nil
+}
+
 // GetAuthConfig returns an auth.Credential for serverAddress.
 func (cfg *Config) GetCredential(serverAddress string) (auth.Credential, error) {
 	cfg.rwLock.RLock()

registry/remote/credentials/internal/config/config_test.go

@@ -925,6 +925,28 @@ func TestConfig_GetCredentialHelper(t *testing.T) {
 	}
 }
 
+func TestConfig_Path(t *testing.T) {
+	cfg := Config{
+		path: "/path/to/config.json",
+	}
+	got, err := cfg.Path()
+
+	if err != nil {
+		t.Errorf("Config.GetPath() error = %v", err)
+	}
+	if got != cfg.path {
+		t.Errorf("Config.GetPath() = %v, want %v", got, cfg.path)
+	}
+}
+
+func TestConfig_Path_nil(t *testing.T) {
+	var cfg *Config
+	_, err := cfg.Path()
+	if err == nil {
+		t.Error("expecting error, got nil")
+	}
+}
+
 func TestConfig_CredentialsStore(t *testing.T) {
 	tests := []struct {
 		name       string

registry/remote/credentials/store.go

@@ -167,6 +167,11 @@ func (ds *DynamicStore) IsAuthConfigured() bool {
 	return ds.config.IsAuthConfigured()
 }
 
+// GetConfigPath returns the path to the config file.
+func (ds *DynamicStore) GetConfigPath() (string, error) {
+	return ds.config.Path()
+}
+
 // getHelperSuffix returns the credential helper suffix for the given server
 // address.
 func (ds *DynamicStore) getHelperSuffix(serverAddress string) string {

registry/remote/credentials/store_test.go

@@ -25,6 +25,7 @@ import (
 	"testing"
 
 	"oras.land/oras-go/v2/registry/remote/auth"
+	"oras.land/oras-go/v2/registry/remote/credentials/internal/config"
 	"oras.land/oras-go/v2/registry/remote/credentials/internal/config/configtest"
 )
 
@@ -611,6 +612,30 @@ func Test_DynamicStore_getHelperSuffix(t *testing.T) {
 		})
 	}
 }
+func Test_DynamicStore_GetConfigPath(t *testing.T) {
+	var store DynamicStore
+	var err error
+	path := "../../testdata/credsStore_config.json"
+	store.config, err = config.Load(path)
+	if err != nil {
+		t.Fatal("config.Load() error =", err)
+	}
+	got, err := store.GetConfigPath()
+	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.GetConfigPath()
+	if err == nil {
+		t.Error("expecting error, got nil")
+	}
+}
 
 func Test_DynamicStore_getStore_nativeStore(t *testing.T) {
 	tests := []struct {