restic: split FileType for backend.FileType

Equality of constants is enforced via internal/repository/filetype.go
using compile time checks.

internal/backend/file.go

@@ -7,6 +7,7 @@ import (
 )
 
 // FileType is the type of a file in the backend.
+// Numeric values must match restic.FileType; enforced in internal/repository/filetype.go.
 type FileType uint8
 
 // These are the different data types a backend can store.
@@ -19,6 +20,7 @@ const (
 	ConfigFile
 )
 
+// Keep in sync with restic.FileType.String().
 func (t FileType) String() string {
 	s := "invalid"
 	switch t {

internal/repository/checker.go

@@ -334,7 +334,7 @@ func checkPack(ctx context.Context, r *Repository, id restic.ID, blobs pack.Blob
 	if err != nil {
 		if r.cache != nil {
 			// ignore error as there's not much we can do here
-			_ = r.cache.Forget(backend.Handle{Type: restic.PackFile, Name: id.String()})
+			_ = r.cache.Forget(backend.Handle{Type: backend.PackFile, Name: id.String()})
 		}
 
 		// retry pack verification to detect transient errors

internal/repository/filetype.go

@@ -0,0 +1,17 @@
+package repository
+
+import (
+	"github.com/restic/restic/internal/backend"
+	"github.com/restic/restic/internal/restic"
+)
+
+// Compile-time checks that restic and backend FileType constants match. A constant mismatch
+// would be an out-of-bounds access that is detected by the compiler.
+var (
+	_ = [1]struct{}{}[backend.PackFile-backend.FileType(restic.PackFile)]
+	_ = [1]struct{}{}[backend.KeyFile-backend.FileType(restic.KeyFile)]
+	_ = [1]struct{}{}[backend.LockFile-backend.FileType(restic.LockFile)]
+	_ = [1]struct{}{}[backend.SnapshotFile-backend.FileType(restic.SnapshotFile)]
+	_ = [1]struct{}{}[backend.IndexFile-backend.FileType(restic.IndexFile)]
+	_ = [1]struct{}{}[backend.ConfigFile-backend.FileType(restic.ConfigFile)]
+)

internal/repository/key.go

@@ -269,10 +269,7 @@ func AddKey(ctx context.Context, s *Repository, password, username, hostname str
 
 	id := restic.Hash(buf)
 	// store in repository and return
-	h := backend.Handle{
-		Type: restic.KeyFile,
-		Name: id.String(),
-	}
+	h := backend.Handle{Type: backend.KeyFile, Name: id.String()}
 
 	err = s.be.Save(ctx, h, backend.NewByteReader(buf, s.be.Hasher()))
 	if err != nil {
@@ -289,7 +286,7 @@ func RemoveKey(ctx context.Context, repo *Repository, id restic.ID) error {
 		return errors.New("refusing to remove key currently used to access repository")
 	}
 
-	h := backend.Handle{Type: restic.KeyFile, Name: id.String()}
+	h := backend.Handle{Type: backend.KeyFile, Name: id.String()}
 	return repo.be.Remove(ctx, h)
 }
 

internal/repository/raw.go

@@ -14,7 +14,7 @@ import (
 // If the backend returns data that does not match the id, then the buffer is returned
 // along with an error that is a restic.ErrInvalidData error.
 func (r *Repository) LoadRaw(ctx context.Context, t restic.FileType, id restic.ID) (buf []byte, err error) {
-	h := backend.Handle{Type: t, Name: id.String()}
+	h := backend.Handle{Type: backend.FileType(t), Name: id.String()}
 
 	buf, err = loadRaw(ctx, r.be, h)
 

internal/repository/repository.go

@@ -226,7 +226,7 @@ func sortCachedPacksFirst(cache haver, blobs []*pack.PackedBlob) {
 	noncached := make([]*pack.PackedBlob, 0, len(blobs)/2)
 
 	for _, blob := range blobs {
-		if cache.Has(backend.Handle{Type: restic.PackFile, Name: blob.PackID().String()}) {
+		if cache.Has(backend.Handle{Type: backend.PackFile, Name: blob.PackID().String()}) {
 			cached = append(cached, blob)
 			continue
 		}
@@ -255,7 +255,7 @@ func (r *Repository) LoadBlob(ctx context.Context, bh restic.BlobHandle, buf []b
 	if err != nil {
 		if r.cache != nil {
 			for _, blob := range blobs {
-				h := backend.Handle{Type: restic.PackFile, Name: blob.PackID().String(), IsMetadata: blob.Blob.Type.IsMetadata()}
+				h := backend.Handle{Type: backend.PackFile, Name: blob.PackID().String(), IsMetadata: blob.Blob.Type.IsMetadata()}
 				// ignore errors as there's not much we can do here
 				_ = r.cache.Forget(h)
 			}
@@ -271,7 +271,7 @@ func (r *Repository) loadBlob(ctx context.Context, blobs []*pack.PackedBlob, buf
 	for _, blob := range blobs {
 		debug.Log("blob %v found: %v", blob.Handle(), blob)
 		// load blob from pack
-		h := backend.Handle{Type: restic.PackFile, Name: blob.PackID().String(), IsMetadata: blob.Blob.Type.IsMetadata()}
+		h := backend.Handle{Type: backend.PackFile, Name: blob.PackID().String(), IsMetadata: blob.Blob.Type.IsMetadata()}
 
 		switch {
 		case cap(buf) < int(blob.Blob.Length):
@@ -514,7 +514,7 @@ func (r *Repository) saveUnpacked(ctx context.Context, t restic.FileType, buf []
 	} else {
 		id = restic.Hash(ciphertext)
 	}
-	h := backend.Handle{Type: t, Name: id.String()}
+	h := backend.Handle{Type: backend.FileType(t), Name: id.String()}
 
 	err = r.be.Save(ctx, h, backend.NewByteReader(ciphertext, r.be.Hasher()))
 	if err != nil {
@@ -558,7 +558,7 @@ func (r *internalRepository) RemoveUnpacked(ctx context.Context, t restic.FileTy
 }
 
 func (r *Repository) removeUnpacked(ctx context.Context, t restic.FileType, id restic.ID) error {
-	return r.be.Remove(ctx, backend.Handle{Type: t, Name: id.String()})
+	return r.be.Remove(ctx, backend.Handle{Type: backend.FileType(t), Name: id.String()})
 }
 
 func (r *Repository) WithBlobUploader(ctx context.Context, fn func(ctx context.Context, uploader restic.BlobSaverWithAsync) error) error {
@@ -894,7 +894,7 @@ func (r *Repository) Init(ctx context.Context, version uint, password string, ch
 		return fmt.Errorf("repository version %v too low", version)
 	}
 
-	_, err := r.be.Stat(ctx, backend.Handle{Type: restic.ConfigFile})
+	_, err := r.be.Stat(ctx, backend.Handle{Type: backend.ConfigFile})
 	if err != nil && !r.be.IsNotExist(err) {
 		return err
 	}
@@ -956,7 +956,7 @@ func (r *Repository) KeyID() restic.ID {
 
 // List runs fn for all files of type t in the repo.
 func (r *Repository) List(ctx context.Context, t restic.FileType, fn func(restic.ID, int64) error) error {
-	return r.be.List(ctx, t, func(fi backend.FileInfo) error {
+	return r.be.List(ctx, backend.FileType(t), func(fi backend.FileInfo) error {
 		id, err := restic.ParseID(fi.Name)
 		if err != nil {
 			debug.Log("unable to parse %v as an ID", fi.Name)
@@ -968,7 +968,7 @@ func (r *Repository) List(ctx context.Context, t restic.FileType, fn func(restic
 
 // listPack returns blob entries from the pack file header including offsets.
 func (r *Repository) listPack(ctx context.Context, id restic.ID, size int64) (pack.Blobs, error) {
-	h := backend.Handle{Type: restic.PackFile, Name: id.String()}
+	h := backend.Handle{Type: backend.PackFile, Name: id.String()}
 
 	entries, _, err := pack.List(r.Key(), backend.ReaderAt(ctx, r.be, h), size)
 	if err != nil {
@@ -1143,7 +1143,7 @@ func streamPack(ctx context.Context, beLoad backendLoadFn, loadBlobFn loadBlobFn
 }
 
 func streamPackPart(ctx context.Context, beLoad backendLoadFn, loadBlobFn loadBlobFn, dec *zstd.Decoder, key *crypto.Key, packID restic.ID, blobs pack.Blobs, handleBlobFn func(blob restic.BlobHandle, buf []byte, err error) error) error {
-	h := backend.Handle{Type: restic.PackFile, Name: packID.String(), IsMetadata: blobs[0].Type.IsMetadata()}
+	h := backend.Handle{Type: backend.PackFile, Name: packID.String(), IsMetadata: blobs[0].Type.IsMetadata()}
 
 	dataStart := blobs[0].Offset
 	dataEnd := blobs[len(blobs)-1].Offset + blobs[len(blobs)-1].Length

internal/repository/warmup.go

@@ -26,10 +26,7 @@ func (job *warmupJob) Wait(ctx context.Context) error {
 func (r *Repository) StartWarmup(ctx context.Context, packs restic.IDSet) (restic.WarmupJob, error) {
 	handles := make([]backend.Handle, 0, len(packs))
 	for pack := range packs {
-		handles = append(
-			handles,
-			backend.Handle{Type: restic.PackFile, Name: pack.String()},
-		)
+		handles = append(handles, backend.Handle{Type: backend.PackFile, Name: pack.String()})
 	}
 	handlesWarmingUp, err := r.be.Warmup(ctx, handles)
 	return &warmupJob{

internal/restic/filetype.go

@@ -0,0 +1,57 @@
+package restic
+
+// FileType is the type of a file in the repository.
+// Numeric values must match backend.FileType; enforced in internal/repository/filetype.go.
+type FileType uint8
+
+// These are the different data types a backend can store.
+const (
+	PackFile FileType = 1 + iota
+	KeyFile
+	LockFile
+	SnapshotFile
+	IndexFile
+	ConfigFile
+)
+
+// Keep in sync with backend.FileType.String().
+func (t FileType) String() string {
+	s := "invalid"
+	switch t {
+	case PackFile:
+		// Spelled "data" instead of "pack" for historical reasons.
+		s = "data"
+	case KeyFile:
+		s = "key"
+	case LockFile:
+		s = "lock"
+	case SnapshotFile:
+		s = "snapshot"
+	case IndexFile:
+		s = "index"
+	case ConfigFile:
+		s = "config"
+	}
+	return s
+}
+
+// WriteableFileType defines the different data types that can be modified via SaveUnpacked or RemoveUnpacked.
+type WriteableFileType FileType
+
+const (
+	// WriteableSnapshotFile is the WriteableFileType for snapshots.
+	WriteableSnapshotFile = WriteableFileType(SnapshotFile)
+)
+
+func (w *WriteableFileType) ToFileType() FileType {
+	switch *w {
+	case WriteableSnapshotFile:
+		return SnapshotFile
+	default:
+		panic("invalid WriteableFileType")
+	}
+}
+
+type FileTypes interface {
+	FileType | WriteableFileType
+}

internal/restic/repository.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"iter"
 
-	"github.com/restic/restic/internal/backend"
 	"github.com/restic/restic/internal/errors"
 )
 
@@ -60,41 +59,6 @@ type Repository interface {
 	StartWarmup(ctx context.Context, packs IDSet) (WarmupJob, error)
 }
 
-type FileType = backend.FileType
-
-// These are the different data types a backend can store. Only filetypes contained
-// in the `WriteableFileType` subset can be modified via the Repository interface.
-// All other filetypes are considered internal datastructures of the Repository.
-const (
-	PackFile     = backend.PackFile
-	KeyFile      = backend.KeyFile
-	LockFile     = backend.LockFile
-	SnapshotFile = backend.SnapshotFile
-	IndexFile    = backend.IndexFile
-	ConfigFile   = backend.ConfigFile
-)
-
-// WriteableFileType defines the different data types that can be modified via SaveUnpacked or RemoveUnpacked.
-type WriteableFileType backend.FileType
-
-const (
-	// WriteableSnapshotFile is the WriteableFileType for snapshots.
-	WriteableSnapshotFile = WriteableFileType(SnapshotFile)
-)
-
-func (w *WriteableFileType) ToFileType() FileType {
-	switch *w {
-	case WriteableSnapshotFile:
-		return SnapshotFile
-	default:
-		panic("invalid WriteableFileType")
-	}
-}
-
-type FileTypes interface {
-	FileType | WriteableFileType
-}
-
 // LoaderUnpacked allows loading a blob not stored in a pack file
 type LoaderUnpacked interface {
 	// Connections returns the maximum number of concurrent backend operations