acd,box,onedrive,opendrive,ploud: fix Features() retaining the original receiver

Before this change the Features() method would return a different Fs
to that the Features() method was called on if the remote was
instantiated on a file.

The practical effect of this is that optional features, eg `rclone
about` wouldn't work properly when called on a file, and likely this
has been causing low level problems for users of these backends for
ages.

Ideally there would be a test for this, but it turns out that this is
really hard, so instead of that all the backends have been converted
to not copy the Fs and a big warning comment inserted for future
readers.

Fixes #2182

backend/amazonclouddrive/amazonclouddrive.go

@@ -312,16 +312,16 @@ func NewFs(name, root string, m configmap.Mapper) (fs.Fs, error) {
 	if err != nil {
 		// Assume it is a file
 		newRoot, remote := dircache.SplitPath(root)
-		newF := *f
-		newF.dirCache = dircache.New(newRoot, f.trueRootID, &newF)
-		newF.root = newRoot
+		tempF := *f
+		tempF.dirCache = dircache.New(newRoot, f.trueRootID, &tempF)
+		tempF.root = newRoot
 		// Make new Fs which is the parent
-		err = newF.dirCache.FindRoot(false)
+		err = tempF.dirCache.FindRoot(false)
 		if err != nil {
 			// No root so return old f
 			return f, nil
 		}
-		_, err := newF.newObjectWithInfo(remote, nil)
+		_, err := tempF.newObjectWithInfo(remote, nil)
 		if err != nil {
 			if err == fs.ErrorObjectNotFound {
 				// File doesn't exist so return old f
@@ -329,8 +329,13 @@ func NewFs(name, root string, m configmap.Mapper) (fs.Fs, error) {
 			}
 			return nil, err
 		}
+		// XXX: update the old f here instead of returning tempF, since
+		// `features` were already filled with functions having *f as a receiver.
+		// See https://github.com/ncw/rclone/issues/2182
+		f.dirCache = tempF.dirCache
+		f.root = tempF.root
 		// return an error with an fs which points to the parent
-		return &newF, fs.ErrorIsFile
+		return f, fs.ErrorIsFile
 	}
 	return f, nil
 }

backend/box/box.go

@@ -283,16 +283,16 @@ func NewFs(name, root string, m configmap.Mapper) (fs.Fs, error) {
 	if err != nil {
 		// Assume it is a file
 		newRoot, remote := dircache.SplitPath(root)
-		newF := *f
-		newF.dirCache = dircache.New(newRoot, rootID, &newF)
-		newF.root = newRoot
+		tempF := *f
+		tempF.dirCache = dircache.New(newRoot, rootID, &tempF)
+		tempF.root = newRoot
 		// Make new Fs which is the parent
-		err = newF.dirCache.FindRoot(false)
+		err = tempF.dirCache.FindRoot(false)
 		if err != nil {
 			// No root so return old f
 			return f, nil
 		}
-		_, err := newF.newObjectWithInfo(remote, nil)
+		_, err := tempF.newObjectWithInfo(remote, nil)
 		if err != nil {
 			if err == fs.ErrorObjectNotFound {
 				// File doesn't exist so return old f
@@ -300,9 +300,14 @@ func NewFs(name, root string, m configmap.Mapper) (fs.Fs, error) {
 			}
 			return nil, err
 		}
-		f.features.Fill(&newF)
+		f.features.Fill(&tempF)
+		// XXX: update the old f here instead of returning tempF, since
+		// `features` were already filled with functions having *f as a receiver.
+		// See https://github.com/ncw/rclone/issues/2182
+		f.dirCache = tempF.dirCache
+		f.root = tempF.root
 		// return an error with an fs which points to the parent
-		return &newF, fs.ErrorIsFile
+		return f, fs.ErrorIsFile
 	}
 	return f, nil
 }

backend/onedrive/onedrive.go

@@ -448,16 +448,16 @@ func NewFs(name, root string, m configmap.Mapper) (fs.Fs, error) {
 	if err != nil {
 		// Assume it is a file
 		newRoot, remote := dircache.SplitPath(root)
-		newF := *f
-		newF.dirCache = dircache.New(newRoot, rootInfo.ID, &newF)
-		newF.root = newRoot
+		tempF := *f
+		tempF.dirCache = dircache.New(newRoot, rootInfo.ID, &tempF)
+		tempF.root = newRoot
 		// Make new Fs which is the parent
-		err = newF.dirCache.FindRoot(false)
+		err = tempF.dirCache.FindRoot(false)
 		if err != nil {
 			// No root so return old f
 			return f, nil
 		}
-		_, err := newF.newObjectWithInfo(remote, nil)
+		_, err := tempF.newObjectWithInfo(remote, nil)
 		if err != nil {
 			if err == fs.ErrorObjectNotFound {
 				// File doesn't exist so return old f
@@ -465,8 +465,13 @@ func NewFs(name, root string, m configmap.Mapper) (fs.Fs, error) {
 			}
 			return nil, err
 		}
+		// XXX: update the old f here instead of returning tempF, since
+		// `features` were already filled with functions having *f as a receiver.
+		// See https://github.com/ncw/rclone/issues/2182
+		f.dirCache = tempF.dirCache
+		f.root = tempF.root
 		// return an error with an fs which points to the parent
-		return &newF, fs.ErrorIsFile
+		return f, fs.ErrorIsFile
 	}
 	return f, nil
 }

backend/opendrive/opendrive.go

@@ -177,17 +177,17 @@ func NewFs(name, root string, m configmap.Mapper) (fs.Fs, error) {
 	if err != nil {
 		// Assume it is a file
 		newRoot, remote := dircache.SplitPath(root)
-		newF := *f
-		newF.dirCache = dircache.New(newRoot, "0", &newF)
-		newF.root = newRoot
+		tempF := *f
+		tempF.dirCache = dircache.New(newRoot, "0", &tempF)
+		tempF.root = newRoot
 
 		// Make new Fs which is the parent
-		err = newF.dirCache.FindRoot(false)
+		err = tempF.dirCache.FindRoot(false)
 		if err != nil {
 			// No root so return old f
 			return f, nil
 		}
-		_, err := newF.newObjectWithInfo(remote, nil)
+		_, err := tempF.newObjectWithInfo(remote, nil)
 		if err != nil {
 			if err == fs.ErrorObjectNotFound {
 				// File doesn't exist so return old f
@@ -195,8 +195,13 @@ func NewFs(name, root string, m configmap.Mapper) (fs.Fs, error) {
 			}
 			return nil, err
 		}
+		// XXX: update the old f here instead of returning tempF, since
+		// `features` were already filled with functions having *f as a receiver.
+		// See https://github.com/ncw/rclone/issues/2182
+		f.dirCache = tempF.dirCache
+		f.root = tempF.root
 		// return an error with an fs which points to the parent
-		return &newF, fs.ErrorIsFile
+		return f, fs.ErrorIsFile
 	}
 	return f, nil
 }

backend/pcloud/pcloud.go

@@ -276,16 +276,16 @@ func NewFs(name, root string, m configmap.Mapper) (fs.Fs, error) {
 	if err != nil {
 		// Assume it is a file
 		newRoot, remote := dircache.SplitPath(root)
-		newF := *f
-		newF.dirCache = dircache.New(newRoot, rootID, &newF)
-		newF.root = newRoot
+		tempF := *f
+		tempF.dirCache = dircache.New(newRoot, rootID, &tempF)
+		tempF.root = newRoot
 		// Make new Fs which is the parent
-		err = newF.dirCache.FindRoot(false)
+		err = tempF.dirCache.FindRoot(false)
 		if err != nil {
 			// No root so return old f
 			return f, nil
 		}
-		_, err := newF.newObjectWithInfo(remote, nil)
+		_, err := tempF.newObjectWithInfo(remote, nil)
 		if err != nil {
 			if err == fs.ErrorObjectNotFound {
 				// File doesn't exist so return old f
@@ -293,8 +293,13 @@ func NewFs(name, root string, m configmap.Mapper) (fs.Fs, error) {
 			}
 			return nil, err
 		}
+		// XXX: update the old f here instead of returning tempF, since
+		// `features` were already filled with functions having *f as a receiver.
+		// See https://github.com/ncw/rclone/issues/2182
+		f.dirCache = tempF.dirCache
+		f.root = tempF.root
 		// return an error with an fs which points to the parent
-		return &newF, fs.ErrorIsFile
+		return f, fs.ErrorIsFile
 	}
 	return f, nil
 }