backend: Hardcode backend scheme in Factory

Our ParseConfig implementations always expect a specific scheme, thus no
other scheme would work.

cmd/restic/global.go

@@ -100,15 +100,15 @@ var internalGlobalCtx context.Context
 
 func init() {
 	backends := location.NewRegistry()
-	backends.Register("b2", b2.NewFactory())
+	backends.Register(azure.NewFactory())
-	backends.Register("local", local.NewFactory())
+	backends.Register(b2.NewFactory())
-	backends.Register("sftp", sftp.NewFactory())
+	backends.Register(gs.NewFactory())
-	backends.Register("s3", s3.NewFactory())
+	backends.Register(local.NewFactory())
-	backends.Register("gs", gs.NewFactory())
+	backends.Register(rclone.NewFactory())
-	backends.Register("azure", azure.NewFactory())
+	backends.Register(rest.NewFactory())
-	backends.Register("swift", swift.NewFactory())
+	backends.Register(s3.NewFactory())
-	backends.Register("rest", rest.NewFactory())
+	backends.Register(sftp.NewFactory())
-	backends.Register("rclone", rclone.NewFactory())
+	backends.Register(swift.NewFactory())
 	globalOptions.backends = backends
 
 	var cancel context.CancelFunc

internal/backend/azure/azure.go

@@ -45,7 +45,7 @@ const defaultListMaxItems = 5000
 var _ restic.Backend = &Backend{}
 
 func NewFactory() location.Factory {
-	return location.NewHTTPBackendFactory(ParseConfig, location.NoPassword, Create, Open)
+	return location.NewHTTPBackendFactory("azure", ParseConfig, location.NoPassword, Create, Open)
 }
 
 func open(cfg Config, rt http.RoundTripper) (*Backend, error) {

internal/backend/b2/b2.go

@@ -38,7 +38,7 @@ const defaultListMaxItems = 10 * 1000
 var _ restic.Backend = &b2Backend{}
 
 func NewFactory() location.Factory {
-	return location.NewHTTPBackendFactory(ParseConfig, location.NoPassword, Create, Open)
+	return location.NewHTTPBackendFactory("b2", ParseConfig, location.NoPassword, Create, Open)
 }
 
 type sniffingRoundTripper struct {

internal/backend/gs/gs.go

@@ -49,7 +49,7 @@ type Backend struct {
 var _ restic.Backend = &Backend{}
 
 func NewFactory() location.Factory {
-	return location.NewHTTPBackendFactory(ParseConfig, location.NoPassword, Create, Open)
+	return location.NewHTTPBackendFactory("gs", ParseConfig, location.NoPassword, Create, Open)
 }
 
 func getStorageClient(rt http.RoundTripper) (*storage.Client, error) {

internal/backend/local/local.go

@@ -31,7 +31,7 @@ type Local struct {
 var _ restic.Backend = &Local{}
 
 func NewFactory() location.Factory {
-	return location.NewLimitedBackendFactory(ParseConfig, location.NoPassword, limiter.WrapBackendConstructor(Create), limiter.WrapBackendConstructor(Open))
+	return location.NewLimitedBackendFactory("local", ParseConfig, location.NoPassword, limiter.WrapBackendConstructor(Create), limiter.WrapBackendConstructor(Open))
 }
 
 const defaultLayout = "default"

internal/backend/location/display_location_test.go

@@ -10,8 +10,8 @@ import (
 
 func TestStripPassword(t *testing.T) {
 	registry := location.NewRegistry()
-	registry.Register("test",
+	registry.Register(
-		location.NewHTTPBackendFactory[any, restic.Backend](nil,
+		location.NewHTTPBackendFactory[any, restic.Backend]("test", nil,
 			func(s string) string {
 				return "cleaned"
 			}, nil, nil,

internal/backend/location/location_test.go

@@ -14,6 +14,7 @@ type testConfig struct {
 
 func testFactory() location.Factory {
 	return location.NewHTTPBackendFactory[testConfig, restic.Backend](
+		"local",
 		func(s string) (*testConfig, error) {
 			return &testConfig{loc: s}, nil
 		}, nil, nil, nil,
@@ -22,12 +23,12 @@ func testFactory() location.Factory {
 
 func TestParse(t *testing.T) {
 	registry := location.NewRegistry()
-	registry.Register("test", testFactory())
+	registry.Register(testFactory())
 
-	path := "test:example"
+	path := "local:example"
 	u, err := location.Parse(registry, path)
 	test.OK(t, err)
-	test.Equals(t, "test", u.Scheme)
+	test.Equals(t, "local", u.Scheme)
 	test.Equals(t, &testConfig{loc: path}, u.Config)
 }
 
@@ -43,7 +44,7 @@ func TestParseFallback(t *testing.T) {
 	}
 
 	registry := location.NewRegistry()
-	registry.Register("local", testFactory())
+	registry.Register(testFactory())
 
 	for _, path := range fallbackTests {
 		t.Run(path, func(t *testing.T) {

internal/backend/location/registry.go

@@ -18,11 +18,11 @@ func NewRegistry() *Registry {
 	}
 }
 
-func (r *Registry) Register(scheme string, factory Factory) {
+func (r *Registry) Register(factory Factory) {
-	if r.factories[scheme] != nil {
+	if r.factories[factory.Scheme()] != nil {
 		panic("duplicate backend")
 	}
-	r.factories[scheme] = factory
+	r.factories[factory.Scheme()] = factory
 }
 
 func (r *Registry) Lookup(scheme string) Factory {
@@ -30,6 +30,7 @@ func (r *Registry) Lookup(scheme string) Factory {
 }
 
 type Factory interface {
+	Scheme() string
 	ParseConfig(s string) (interface{}, error)
 	StripPassword(s string) string
 	Create(ctx context.Context, cfg interface{}, rt http.RoundTripper, lim limiter.Limiter) (restic.Backend, error)
@@ -37,12 +38,17 @@ type Factory interface {
 }
 
 type genericBackendFactory[C any, T restic.Backend] struct {
+	scheme          string
 	parseConfigFn   func(s string) (*C, error)
 	stripPasswordFn func(s string) string
 	createFn        func(ctx context.Context, cfg C, rt http.RoundTripper, lim limiter.Limiter) (T, error)
 	openFn          func(ctx context.Context, cfg C, rt http.RoundTripper, lim limiter.Limiter) (T, error)
 }
 
+func (f *genericBackendFactory[C, T]) Scheme() string {
+	return f.scheme
+}
+
 func (f *genericBackendFactory[C, T]) ParseConfig(s string) (interface{}, error) {
 	return f.parseConfigFn(s)
 }
@@ -59,12 +65,15 @@ func (f *genericBackendFactory[C, T]) Open(ctx context.Context, cfg interface{},
 	return f.openFn(ctx, *cfg.(*C), rt, lim)
 }
 
-func NewHTTPBackendFactory[C any, T restic.Backend](parseConfigFn func(s string) (*C, error),
+func NewHTTPBackendFactory[C any, T restic.Backend](
+	scheme string,
+	parseConfigFn func(s string) (*C, error),
 	stripPasswordFn func(s string) string,
 	createFn func(ctx context.Context, cfg C, rt http.RoundTripper) (T, error),
 	openFn func(ctx context.Context, cfg C, rt http.RoundTripper) (T, error)) Factory {
 
 	return &genericBackendFactory[C, T]{
+		scheme:          scheme,
 		parseConfigFn:   parseConfigFn,
 		stripPasswordFn: stripPasswordFn,
 		createFn: func(ctx context.Context, cfg C, rt http.RoundTripper, _ limiter.Limiter) (T, error) {
@@ -76,12 +85,15 @@ func NewHTTPBackendFactory[C any, T restic.Backend](parseConfigFn func(s string)
 	}
 }
 
-func NewLimitedBackendFactory[C any, T restic.Backend](parseConfigFn func(s string) (*C, error),
+func NewLimitedBackendFactory[C any, T restic.Backend](
+	scheme string,
+	parseConfigFn func(s string) (*C, error),
 	stripPasswordFn func(s string) string,
 	createFn func(ctx context.Context, cfg C, lim limiter.Limiter) (T, error),
 	openFn func(ctx context.Context, cfg C, lim limiter.Limiter) (T, error)) Factory {
 
 	return &genericBackendFactory[C, T]{
+		scheme:          scheme,
 		parseConfigFn:   parseConfigFn,
 		stripPasswordFn: stripPasswordFn,
 		createFn: func(ctx context.Context, cfg C, _ http.RoundTripper, lim limiter.Limiter) (T, error) {

internal/backend/mem/mem_backend.go

@@ -27,6 +27,7 @@ func NewFactory() location.Factory {
 	be := New()
 
 	return location.NewHTTPBackendFactory[struct{}, *MemoryBackend](
+		"mem",
 		func(s string) (*struct{}, error) {
 			return &struct{}{}, nil
 		},

internal/backend/rclone/backend.go

@@ -38,7 +38,7 @@ type Backend struct {
 }
 
 func NewFactory() location.Factory {
-	return location.NewLimitedBackendFactory(ParseConfig, location.NoPassword, Create, Open)
+	return location.NewLimitedBackendFactory("rclone", ParseConfig, location.NoPassword, Create, Open)
 }
 
 // run starts command with args and initializes the StdioConn.

internal/backend/rest/rest.go

@@ -31,7 +31,7 @@ type Backend struct {
 }
 
 func NewFactory() location.Factory {
-	return location.NewHTTPBackendFactory(ParseConfig, StripPassword, Create, Open)
+	return location.NewHTTPBackendFactory("rest", ParseConfig, StripPassword, Create, Open)
 }
 
 // the REST API protocol version is decided by HTTP request headers, these are the constants.

internal/backend/s3/s3.go

@@ -33,7 +33,7 @@ type Backend struct {
 var _ restic.Backend = &Backend{}
 
 func NewFactory() location.Factory {
-	return location.NewHTTPBackendFactory(ParseConfig, location.NoPassword, Create, Open)
+	return location.NewHTTPBackendFactory("s3", ParseConfig, location.NoPassword, Create, Open)
 }
 
 const defaultLayout = "default"

internal/backend/sftp/sftp.go

@@ -44,7 +44,7 @@ type SFTP struct {
 var _ restic.Backend = &SFTP{}
 
 func NewFactory() location.Factory {
-	return location.NewLimitedBackendFactory(ParseConfig, location.NoPassword, limiter.WrapBackendConstructor(Create), limiter.WrapBackendConstructor(Open))
+	return location.NewLimitedBackendFactory("sftp", ParseConfig, location.NoPassword, limiter.WrapBackendConstructor(Create), limiter.WrapBackendConstructor(Open))
 }
 
 const defaultLayout = "default"

internal/backend/swift/swift.go

@@ -36,7 +36,7 @@ type beSwift struct {
 var _ restic.Backend = &beSwift{}
 
 func NewFactory() location.Factory {
-	return location.NewHTTPBackendFactory(ParseConfig, location.NoPassword, Open, Open)
+	return location.NewHTTPBackendFactory("swift", ParseConfig, location.NoPassword, Open, Open)
 }
 
 // Open opens the swift backend at a container in region. The container is