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

…ath (#674)

Two changes proposed in this PR
1) When failed to fetch credentials for basic auth, return a new error
2) Add a new function to DynamicStore

An example usage of the proposed change: oras-project/oras#1235,
resolves #676

Signed-off-by: Billy Zha <[email protected]>

registry/remote/auth/client.go

@@ -31,6 +31,10 @@ import (
 	"oras.land/oras-go/v2/registry/remote/retry"
 )
 
+// ErrBasicCredentialNotFound is returned  when the credential is not found for
+// basic auth.
+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 @@ func (c *Client) fetchBasicAuth(ctx context.Context, registry string) (string, e
 		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/auth/client_test.go

@@ -3964,3 +3964,15 @@ func TestClient_StaticCredential_withRefreshToken(t *testing.T) {
 		t.Errorf("incorrect error: %v, expected %v", err, expectedError)
 	}
 }
+
+func TestClient_fetchBasicAuth(t *testing.T) {
+	c := &Client{
+		Credential: func(ctx context.Context, registry string) (Credential, error) {
+			return EmptyCredential, nil
+		},
+	}
+	_, err := c.fetchBasicAuth(context.Background(), "")
+	if err != ErrBasicCredentialNotFound {
+		t.Errorf("incorrect error: %v, expected %v", err, ErrBasicCredentialNotFound)
+	}
+}

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

@@ -224,6 +224,11 @@ func (cfg *Config) CredentialsStore() string {
 	return cfg.credentialsStore
 }
 
+// Path returns the path to the config file.
+func (cfg *Config) Path() string {
+	return cfg.path
+}
+
 // SetCredentialsStore puts the configured credentials store.
 func (cfg *Config) SetCredentialsStore(credsStore string) error {
 	cfg.rwLock.Lock()

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

@@ -1450,3 +1450,13 @@ func Test_toHostname(t *testing.T) {
 		})
 	}
 }
+
+func TestConfig_Path(t *testing.T) {
+	mockedPath := "/path/to/config.json"
+	config := Config{
+		path: mockedPath,
+	}
+	if got := config.Path(); got != mockedPath {
+		t.Errorf("Config.Path() = %v, want %v", got, mockedPath)
+	}
+}

registry/remote/credentials/store.go

@@ -167,6 +167,11 @@ func (ds *DynamicStore) IsAuthConfigured() bool {
 	return ds.config.IsAuthConfigured()
 }
 
+// ConfigPath returns the path to the config file.
+func (ds *DynamicStore) ConfigPath() string {
+	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

@@ -612,6 +612,19 @@ func Test_DynamicStore_getHelperSuffix(t *testing.T) {
 	}
 }
 
+func Test_DynamicStore_ConfigPath(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 := store.ConfigPath()
+	if got != path {
+		t.Errorf("Config.GetPath() = %v, want %v", got, path)
+	}
+}
+
 func Test_DynamicStore_getStore_nativeStore(t *testing.T) {
 	tests := []struct {
 		name          string