Fix mfs touch and chmod

Fixes #660

Author: gammazero

ipld/unixfs/unixfs.go

@@ -36,6 +36,7 @@ const (
 // Common errors
 var (
 	ErrMalformedFileFormat = errors.New("malformed data in file format")
+	ErrNotProtoNode        = errors.New("expected a ProtoNode as internal node")
 	ErrUnrecognizedType    = errors.New("unrecognized node type")
 )
 
@@ -544,7 +545,7 @@ func ReadUnixFSNodeData(node ipld.Node) (data []byte, err error) {
 func ExtractFSNode(node ipld.Node) (*FSNode, error) {
 	protoNode, ok := node.(*dag.ProtoNode)
 	if !ok {
-		return nil, errors.New("expected a ProtoNode as internal node")
+		return nil, ErrNotProtoNode
 	}
 
 	fsNode, err := FSNodeFromBytes(protoNode.Data())

mfs/file.go

@@ -185,14 +185,14 @@ func (fi *File) Mode() (os.FileMode, error) {
 	defer fi.nodeLock.RUnlock()
 
 	nd, err := fi.GetNode()
-	if err == nil {
-		fsn, err := ft.ExtractFSNode(nd)
-		if err == nil {
-			return fsn.Mode() & 0xFFF, nil
-		}
+	if err != nil {
+		return 0, err
 	}
-
-	return 0, err
+	fsn, err := ft.ExtractFSNode(nd)
+	if err != nil {
+		return 0, err
+	}
+	return fsn.Mode() & 0xFFF, nil
 }
 
 func (fi *File) SetMode(mode os.FileMode) error {
@@ -203,6 +203,11 @@ func (fi *File) SetMode(mode os.FileMode) error {
 
 	fsn, err := ft.ExtractFSNode(nd)
 	if err != nil {
+		if errors.Is(err, ft.ErrNotProtoNode) {
+			// Wrap raw node in protonode.
+			data := nd.RawData()
+			return fi.setNodeData(ft.FilePBDataWithStat(data, uint64(len(data)), mode, time.Time{}))
+		}
 		return err
 	}
 
@@ -221,14 +226,14 @@ func (fi *File) ModTime() (time.Time, error) {
 	defer fi.nodeLock.RUnlock()
 
 	nd, err := fi.GetNode()
-	if err == nil {
-		fsn, err := ft.ExtractFSNode(nd)
-		if err == nil {
-			return fsn.ModTime(), nil
-		}
+	if err != nil {
+		return time.Time{}, err
 	}
-
-	return time.Time{}, err
+	fsn, err := ft.ExtractFSNode(nd)
+	if err != nil {
+		return time.Time{}, err
+	}
+	return fsn.ModTime(), nil
 }
 
 // SetModTime sets the files' last modification time
@@ -240,6 +245,11 @@ func (fi *File) SetModTime(ts time.Time) error {
 
 	fsn, err := ft.ExtractFSNode(nd)
 	if err != nil {
+		if errors.Is(err, ft.ErrNotProtoNode) {
+			// Wrap raw node in protonode.
+			data := nd.RawData()
+			return fi.setNodeData(ft.FilePBDataWithStat(data, uint64(len(data)), 0, ts))
+		}
 		return err
 	}
 
@@ -267,3 +277,8 @@ func (fi *File) setNodeData(data []byte) error {
 
 	return parent.updateChildEntry(child{name, fi.node})
 }
+
+func (fi *File) replaceRawNodeWithStatNode(data []byte, mode os.FileMode, mtime time.Time) error {
+	data = ft.FilePBDataWithStat(data, uint64(len(data)), mode, mtime)
+	return fi.setNodeData(data)
+}