Centralize storage walk emission

internal/adapters/local/backend.go

@@ -161,31 +161,10 @@ func (b *Backend) Walk(ctx context.Context, prefix string, opts storage.WalkOpti
 		}
 		return b.translateError(storage.OpWalk, prefix, err)
 	}
-	visited := 0
-	emit := func(entry storage.Entry) error {
-		if err := ctx.Err(); err != nil {
-			return err
-		}
-		if opts.Limit > 0 && visited >= opts.Limit {
-			return storage.ErrStopWalk
-		}
-		visited++
-		if err := fn(entry); err != nil {
-			if errors.Is(err, storage.ErrStopWalk) {
-				return storage.ErrStopWalk
-			}
-			return storage.NewError(storage.OpWalk, backendName, entry.Path, storage.ErrUnknown, err)
-		}
-		return nil
-	}
+	emitter := storage.NewWalkEmitter(ctx, backendName, opts, fn)
 
 	if !info.IsDir() {
-		if err := emit(entryFromInfo(prefix, info)); errors.Is(err, storage.ErrStopWalk) {
-			return nil
-		} else if err != nil {
-			return err
-		}
-		return nil
+		return storage.FinishWalk(emitter.Emit(entryFromInfo(prefix, info)))
 	}
 
 	walkErr := filepath.WalkDir(nativePrefix, func(nativePath string, dirEntry fs.DirEntry, err error) error {
@@ -210,24 +189,13 @@ func (b *Backend) Walk(ctx context.Context, prefix string, opts storage.WalkOpti
 		if err != nil {
 			return b.translateError(storage.OpWalk, logicalPath, err)
 		}
-		return emit(entryFromInfo(logicalPath, info))
+		return emitter.Emit(entryFromInfo(logicalPath, info))
 	})
-	if errors.Is(walkErr, storage.ErrStopWalk) {
-		return nil
-	}
-	return walkErr
+	return storage.FinishWalk(walkErr)
 }
 
 func (b *Backend) HasAny(ctx context.Context, prefix string) (bool, error) {
-	found := false
-	err := b.Walk(ctx, prefix, storage.WalkOptions{Recursive: false, Limit: 1}, func(storage.Entry) error {
-		found = true
-		return storage.ErrStopWalk
-	})
-	if err != nil {
-		return false, err
-	}
-	return found, nil
+	return storage.HasAny(ctx, b, prefix)
 }
 
 func (b *Backend) DeleteManagedBundle(ctx context.Context, bundlePath string, managedOutputPaths []string, opts storage.DeleteOptions) error {