Centralize storage walk emission

internal/adapters/s3/backend.go

@@ -183,55 +183,25 @@ func (b *Backend) Walk(ctx context.Context, logicalPrefix string, opts storage.W
 	if err := storage.ValidatePrefix(logicalPrefix); err != nil {
 		return 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 logicalPrefix != "" {
 		entry, err := b.Stat(ctx, logicalPrefix)
 		if err == nil {
-			if err := emit(entry); errors.Is(err, storage.ErrStopWalk) {
-				return nil
-			} else if err != nil {
-				return err
+			if err := emitter.Emit(entry); err != nil {
+				return storage.FinishWalk(err)
 			}
-			if opts.Limit > 0 && visited >= opts.Limit {
+			if emitter.LimitReached() {
 				return nil
 			}
 		} else if !storage.IsNotFound(err) {
 			return err
 		}
 	}
-	err := b.walkObjects(ctx, logicalPrefix, opts, emit)
-	if errors.Is(err, storage.ErrStopWalk) {
-		return nil
-	}
-	return err
+	return storage.FinishWalk(b.walkObjects(ctx, logicalPrefix, opts, emitter.Emit))
 }
 
 func (b *Backend) HasAny(ctx context.Context, logicalPrefix string) (bool, error) {
-	found := false
-	err := b.Walk(ctx, logicalPrefix, 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, logicalPrefix)
 }
 
 func (b *Backend) DeleteManagedBundle(ctx context.Context, bundlePath string, managedOutputPaths []string, opts storage.DeleteOptions) error {