backend: let ParseConfig return concrete type

internal/backend/azure/azure_test.go

@@ -30,12 +30,11 @@ func newAzureTestSuite(t testing.TB) *test.Suite {
 
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
 		NewConfig: func() (interface{}, error) {
-			azcfg, err := azure.ParseConfig(os.Getenv("RESTIC_TEST_AZURE_REPOSITORY"))
+			cfg, err := azure.ParseConfig(os.Getenv("RESTIC_TEST_AZURE_REPOSITORY"))
 			if err != nil {
 				return nil, err
 			}
 
-			cfg := azcfg.(azure.Config)
 			cfg.AccountName = os.Getenv("RESTIC_TEST_AZURE_ACCOUNT_NAME")
 			cfg.AccountKey = options.NewSecretString(os.Getenv("RESTIC_TEST_AZURE_ACCOUNT_KEY"))
 			cfg.Prefix = fmt.Sprintf("test-%d", time.Now().UnixNano())
@@ -141,12 +140,11 @@ func TestUploadLargeFile(t *testing.T) {
 		return
 	}
 
-	azcfg, err := azure.ParseConfig(os.Getenv("RESTIC_TEST_AZURE_REPOSITORY"))
+	cfg, err := azure.ParseConfig(os.Getenv("RESTIC_TEST_AZURE_REPOSITORY"))
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	cfg := azcfg.(azure.Config)
 	cfg.AccountName = os.Getenv("RESTIC_TEST_AZURE_ACCOUNT_NAME")
 	cfg.AccountKey = options.NewSecretString(os.Getenv("RESTIC_TEST_AZURE_ACCOUNT_KEY"))
 	cfg.Prefix = fmt.Sprintf("test-upload-large-%d", time.Now().UnixNano())

internal/backend/azure/config.go

@@ -34,9 +34,9 @@ func init() {
 
 // ParseConfig parses the string s and extracts the azure config. The
 // configuration format is azure:containerName:/[prefix].
-func ParseConfig(s string) (interface{}, error) {
+func ParseConfig(s string) (Config, error) {
 	if !strings.HasPrefix(s, "azure:") {
-		return nil, errors.New("azure: invalid format")
+		return Config{}, errors.New("azure: invalid format")
 	}
 
 	// strip prefix "azure:"
@@ -46,7 +46,7 @@ func ParseConfig(s string) (interface{}, error) {
 	// remainder as prefix
 	container, prefix, colon := strings.Cut(s, ":")
 	if !colon {
-		return nil, errors.New("azure: invalid format: bucket name or path not found")
+		return Config{}, errors.New("azure: invalid format: bucket name or path not found")
 	}
 	prefix = strings.TrimPrefix(path.Clean(prefix), "/")
 	cfg := NewConfig()

internal/backend/b2/b2_test.go

@@ -31,12 +31,11 @@ func newB2TestSuite(t testing.TB) *test.Suite {
 
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
 		NewConfig: func() (interface{}, error) {
-			b2cfg, err := b2.ParseConfig(os.Getenv("RESTIC_TEST_B2_REPOSITORY"))
+			cfg, err := b2.ParseConfig(os.Getenv("RESTIC_TEST_B2_REPOSITORY"))
 			if err != nil {
 				return nil, err
 			}
 
-			cfg := b2cfg.(b2.Config)
 			cfg.AccountID = os.Getenv("RESTIC_TEST_B2_ACCOUNT_ID")
 			cfg.Key = options.NewSecretString(os.Getenv("RESTIC_TEST_B2_ACCOUNT_KEY"))
 			cfg.Prefix = fmt.Sprintf("test-%d", time.Now().UnixNano())

internal/backend/b2/config.go

@@ -59,15 +59,15 @@ func checkBucketName(name string) error {
 // ParseConfig parses the string s and extracts the b2 config. The supported
 // configuration format is b2:bucketname/prefix. If no prefix is given the
 // prefix "restic" will be used.
-func ParseConfig(s string) (interface{}, error) {
+func ParseConfig(s string) (Config, error) {
 	if !strings.HasPrefix(s, "b2:") {
-		return nil, errors.New("invalid format, want: b2:bucket-name[:path]")
+		return Config{}, errors.New("invalid format, want: b2:bucket-name[:path]")
 	}
 
 	s = s[3:]
 	bucket, prefix, _ := strings.Cut(s, ":")
 	if err := checkBucketName(bucket); err != nil {
-		return nil, err
+		return Config{}, err
 	}
 
 	if len(prefix) > 0 {

internal/backend/gs/config.go

@@ -35,9 +35,9 @@ func init() {
 
 // ParseConfig parses the string s and extracts the gcs config. The
 // supported configuration format is gs:bucketName:/[prefix].
-func ParseConfig(s string) (interface{}, error) {
+func ParseConfig(s string) (Config, error) {
 	if !strings.HasPrefix(s, "gs:") {
-		return nil, errors.New("gs: invalid format")
+		return Config{}, errors.New("gs: invalid format")
 	}
 
 	// strip prefix "gs:"
@@ -47,7 +47,7 @@ func ParseConfig(s string) (interface{}, error) {
 	// remainder as prefix
 	bucket, prefix, colon := strings.Cut(s, ":")
 	if !colon {
-		return nil, errors.New("gs: invalid format: bucket name or path not found")
+		return Config{}, errors.New("gs: invalid format: bucket name or path not found")
 	}
 
 	prefix = strings.TrimPrefix(path.Clean(prefix), "/")

internal/backend/gs/gs_test.go

@@ -27,12 +27,11 @@ func newGSTestSuite(t testing.TB) *test.Suite {
 
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
 		NewConfig: func() (interface{}, error) {
-			gscfg, err := gs.ParseConfig(os.Getenv("RESTIC_TEST_GS_REPOSITORY"))
+			cfg, err := gs.ParseConfig(os.Getenv("RESTIC_TEST_GS_REPOSITORY"))
 			if err != nil {
 				return nil, err
 			}
 
-			cfg := gscfg.(gs.Config)
 			cfg.ProjectID = os.Getenv("RESTIC_TEST_GS_PROJECT_ID")
 			cfg.Prefix = fmt.Sprintf("test-%d", time.Now().UnixNano())
 			return cfg, nil

internal/backend/local/config.go

@@ -27,9 +27,9 @@ func init() {
 }
 
 // ParseConfig parses a local backend config.
-func ParseConfig(s string) (interface{}, error) {
+func ParseConfig(s string) (Config, error) {
 	if !strings.HasPrefix(s, "local:") {
-		return nil, errors.New(`invalid format, prefix "local" not found`)
+		return Config{}, errors.New(`invalid format, prefix "local" not found`)
 	}
 
 	cfg := NewConfig()

internal/backend/location/location.go

@@ -29,18 +29,24 @@ type parser struct {
 	stripPassword func(string) string
 }
 
+func configToAny[C any](parser func(string) (C, error)) func(string) (interface{}, error) {
+	return func(s string) (interface{}, error) {
+		return parser(s)
+	}
+}
+
 // parsers is a list of valid config parsers for the backends. The first parser
 // is the fallback and should always be set to the local backend.
 var parsers = []parser{
-	{"b2", b2.ParseConfig, noPassword},
+	{"b2", configToAny(b2.ParseConfig), noPassword},
-	{"local", local.ParseConfig, noPassword},
+	{"local", configToAny(local.ParseConfig), noPassword},
-	{"sftp", sftp.ParseConfig, noPassword},
+	{"sftp", configToAny(sftp.ParseConfig), noPassword},
-	{"s3", s3.ParseConfig, noPassword},
+	{"s3", configToAny(s3.ParseConfig), noPassword},
-	{"gs", gs.ParseConfig, noPassword},
+	{"gs", configToAny(gs.ParseConfig), noPassword},
-	{"azure", azure.ParseConfig, noPassword},
+	{"azure", configToAny(azure.ParseConfig), noPassword},
-	{"swift", swift.ParseConfig, noPassword},
+	{"swift", configToAny(swift.ParseConfig), noPassword},
-	{"rest", rest.ParseConfig, rest.StripPassword},
+	{"rest", configToAny(rest.ParseConfig), rest.StripPassword},
-	{"rclone", rclone.ParseConfig, noPassword},
+	{"rclone", configToAny(rclone.ParseConfig), noPassword},
 }
 
 // noPassword returns the repository location unchanged (there's no sensitive information there)

internal/backend/rclone/config.go

@@ -34,9 +34,9 @@ func NewConfig() Config {
 }
 
 // ParseConfig parses the string s and extracts the remote server URL.
-func ParseConfig(s string) (interface{}, error) {
+func ParseConfig(s string) (Config, error) {
 	if !strings.HasPrefix(s, "rclone:") {
-		return nil, errors.New("invalid rclone backend specification")
+		return Config{}, errors.New("invalid rclone backend specification")
 	}
 
 	s = s[7:]

internal/backend/rest/config.go

@@ -26,16 +26,16 @@ func NewConfig() Config {
 }
 
 // ParseConfig parses the string s and extracts the REST server URL.
-func ParseConfig(s string) (interface{}, error) {
+func ParseConfig(s string) (Config, error) {
 	if !strings.HasPrefix(s, "rest:") {
-		return nil, errors.New("invalid REST backend specification")
+		return Config{}, errors.New("invalid REST backend specification")
 	}
 
 	s = prepareURL(s)
 
 	u, err := url.Parse(s)
 	if err != nil {
-		return nil, errors.WithStack(err)
+		return Config{}, errors.WithStack(err)
 	}
 
 	cfg := NewConfig()

internal/backend/rest/rest_test.go

@@ -130,12 +130,10 @@ func TestBackendRESTExternalServer(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	c := cfg.(rest.Config)
-
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
 
-	newTestSuite(ctx, t, c.URL, true).RunTests(t)
+	newTestSuite(ctx, t, cfg.URL, true).RunTests(t)
 }
 
 func BenchmarkBackendREST(t *testing.B) {

internal/backend/s3/config.go

@@ -45,7 +45,7 @@ func init() {
 // supported configuration formats are s3://host/bucketname/prefix and
 // s3:host/bucketname/prefix. The host can also be a valid s3 region
 // name. If no prefix is given the prefix "restic" will be used.
-func ParseConfig(s string) (interface{}, error) {
+func ParseConfig(s string) (Config, error) {
 	switch {
 	case strings.HasPrefix(s, "s3:http"):
 		// assume that a URL has been specified, parse it and
@@ -53,11 +53,11 @@ func ParseConfig(s string) (interface{}, error) {
 		// bucket name and prefix
 		url, err := url.Parse(s[3:])
 		if err != nil {
-			return nil, errors.WithStack(err)
+			return Config{}, errors.WithStack(err)
 		}
 
 		if url.Path == "" {
-			return nil, errors.New("s3: bucket name not found")
+			return Config{}, errors.New("s3: bucket name not found")
 		}
 
 		bucket, path, _ := strings.Cut(url.Path[1:], "/")
@@ -67,7 +67,7 @@ func ParseConfig(s string) (interface{}, error) {
 	case strings.HasPrefix(s, "s3:"):
 		s = s[3:]
 	default:
-		return nil, errors.New("s3: invalid format")
+		return Config{}, errors.New("s3: invalid format")
 	}
 	// use the first entry of the path as the endpoint and the
 	// remainder as bucket name and prefix
@@ -76,9 +76,9 @@ func ParseConfig(s string) (interface{}, error) {
 	return createConfig(endpoint, bucket, prefix, false)
 }
 
-func createConfig(endpoint, bucket, prefix string, useHTTP bool) (interface{}, error) {
+func createConfig(endpoint, bucket, prefix string, useHTTP bool) (Config, error) {
 	if endpoint == "" {
-		return nil, errors.New("s3: invalid format, host/region or bucket name not found")
+		return Config{}, errors.New("s3: invalid format, host/region or bucket name not found")
 	}
 
 	if prefix != "" {

internal/backend/s3/s3_test.go

@@ -229,12 +229,11 @@ func newS3TestSuite(t testing.TB) *test.Suite {
 
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
 		NewConfig: func() (interface{}, error) {
-			s3cfg, err := s3.ParseConfig(os.Getenv("RESTIC_TEST_S3_REPOSITORY"))
+			cfg, err := s3.ParseConfig(os.Getenv("RESTIC_TEST_S3_REPOSITORY"))
 			if err != nil {
 				return nil, err
 			}
 
-			cfg := s3cfg.(s3.Config)
 			cfg.KeyID = os.Getenv("RESTIC_TEST_S3_KEY")
 			cfg.Secret = options.NewSecretString(os.Getenv("RESTIC_TEST_S3_SECRET"))
 			cfg.Prefix = fmt.Sprintf("test-%d", time.Now().UnixNano())

internal/backend/sftp/config.go

@@ -35,14 +35,14 @@ func init() {
 // and sftp:user@host:directory.  The directory will be path Cleaned and can
 // be an absolute path if it starts with a '/' (e.g.
 // sftp://user@host//absolute and sftp:user@host:/absolute).
-func ParseConfig(s string) (interface{}, error) {
+func ParseConfig(s string) (Config, error) {
 	var user, host, port, dir string
 	switch {
 	case strings.HasPrefix(s, "sftp://"):
 		// parse the "sftp://user@host/path" url format
 		url, err := url.Parse(s)
 		if err != nil {
-			return nil, errors.WithStack(err)
+			return Config{}, errors.WithStack(err)
 		}
 		if url.User != nil {
 			user = url.User.Username()
@@ -51,7 +51,7 @@ func ParseConfig(s string) (interface{}, error) {
 		port = url.Port()
 		dir = url.Path
 		if dir == "" {
-			return nil, errors.Errorf("invalid backend %q, no directory specified", s)
+			return Config{}, errors.Errorf("invalid backend %q, no directory specified", s)
 		}
 
 		dir = dir[1:]
@@ -63,7 +63,7 @@ func ParseConfig(s string) (interface{}, error) {
 		var colon bool
 		host, dir, colon = strings.Cut(s, ":")
 		if !colon {
-			return nil, errors.New("sftp: invalid format, hostname or path not found")
+			return Config{}, errors.New("sftp: invalid format, hostname or path not found")
 		}
 		// split user and host at the "@"
 		data := strings.SplitN(host, "@", 3)
@@ -75,12 +75,12 @@ func ParseConfig(s string) (interface{}, error) {
 			host = data[1]
 		}
 	default:
-		return nil, errors.New(`invalid format, does not start with "sftp:"`)
+		return Config{}, errors.New(`invalid format, does not start with "sftp:"`)
 	}
 
 	p := path.Clean(dir)
 	if strings.HasPrefix(p, "~") {
-		return nil, errors.New("sftp path starts with the tilde (~) character, that fails for most sftp servers.\nUse a relative directory, most servers interpret this as relative to the user's home directory")
+		return Config{}, errors.New("sftp path starts with the tilde (~) character, that fails for most sftp servers.\nUse a relative directory, most servers interpret this as relative to the user's home directory")
 	}
 
 	cfg := NewConfig()

internal/backend/swift/config.go

@@ -50,19 +50,19 @@ func NewConfig() Config {
 }
 
 // ParseConfig parses the string s and extract swift's container name and prefix.
-func ParseConfig(s string) (interface{}, error) {
+func ParseConfig(s string) (Config, error) {
 	if !strings.HasPrefix(s, "swift:") {
-		return nil, errors.New("invalid URL, expected: swift:container-name:/[prefix]")
+		return Config{}, errors.New("invalid URL, expected: swift:container-name:/[prefix]")
 	}
 	s = strings.TrimPrefix(s, "swift:")
 
 	container, prefix, _ := strings.Cut(s, ":")
 	if prefix == "" {
-		return nil, errors.Errorf("prefix is empty")
+		return Config{}, errors.Errorf("prefix is empty")
 	}
 
 	if prefix[0] != '/' {
-		return nil, errors.Errorf("prefix does not start with slash (/)")
+		return Config{}, errors.Errorf("prefix does not start with slash (/)")
 	}
 	prefix = prefix[1:]
 

internal/backend/swift/config_test.go

@@ -33,16 +33,11 @@ var configTests = []struct {
 func TestParseConfig(t *testing.T) {
 	for _, test := range configTests {
 		t.Run("", func(t *testing.T) {
-			v, err := ParseConfig(test.s)
+			cfg, err := ParseConfig(test.s)
 			if err != nil {
 				t.Fatalf("parsing %q failed: %v", test.s, err)
 			}
 
-			cfg, ok := v.(Config)
-			if !ok {
-				t.Fatalf("wrong type returned, want Config, got %T", cfg)
-			}
-
 			if cfg != test.cfg {
 				t.Fatalf("wrong output for %q, want:\n  %#v\ngot:\n  %#v",
 					test.s, test.cfg, cfg)

internal/backend/swift/swift_test.go

@@ -43,12 +43,11 @@ func newSwiftTestSuite(t testing.TB) *test.Suite {
 
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
 		NewConfig: func() (interface{}, error) {
-			swiftcfg, err := swift.ParseConfig(os.Getenv("RESTIC_TEST_SWIFT"))
+			cfg, err := swift.ParseConfig(os.Getenv("RESTIC_TEST_SWIFT"))
 			if err != nil {
 				return nil, err
 			}
 
-			cfg := swiftcfg.(swift.Config)
 			if err = swift.ApplyEnvironment("RESTIC_TEST_", &cfg); err != nil {
 				return nil, err
 			}