Add placeholder support for ListR interface.

The ListR interface will be implemented by remotes that can do a
recursive directory listing more efficiently than just recursing
through the directories.  These include the bucket based remotes.

b2/b2.go

@@ -595,6 +595,12 @@ func (f *Fs) List(out fs.ListOpts, dir string) {
 	return
 }
 
+// ListR lists the objects and directories of the Fs starting
+// from dir recursively into out.
+func (f *Fs) ListR(out fs.ListOpts, dir string) {
+	f.List(out, dir) // FIXME
+}
+
 // listBucketFn is called from listBucketsToFn to handle a bucket
 type listBucketFn func(*api.Bucket) error
 
@@ -1365,6 +1371,7 @@ var (
 	_ fs.Fs         = &Fs{}
 	_ fs.Purger     = &Fs{}
 	_ fs.CleanUpper = &Fs{}
+	_ fs.ListRer    = &Fs{}
 	_ fs.Object     = &Object{}
 	_ fs.MimeTyper  = &Object{}
 )

dropbox/dropbox.go

@@ -16,6 +16,9 @@ API v1, and at least the last path component will have the correct
 casing. Changes to only the casing of paths won't be returned by
 list_folder/continue. This field will be null if the file or folder is
 not mounted. This field is optional.
+
+This only becomes a problem if dropbox implements the ListR interface
+which it currently doesn't.
 */
 
 import (

fs/fs.go

@@ -295,6 +295,19 @@ type Features struct {
 	// Implement this if you have a way of emptying the trash or
 	// otherwise cleaning up old versions of files.
 	CleanUp func() error
+
+	// ListR lists the objects and directories of the Fs starting
+	// from dir recursively into out.
+	//
+	// dir should be "" to start from the root, and should not
+	// have trailing slashes.
+	//
+	// This should return ErrDirNotFound (using out.SetError())
+	// if the directory isn't found.
+	//
+	// Don't implement this unless you have a more efficient way
+	// of listing recursively that doing a directory traversal.
+	ListR func(out ListOpts, dir string)
 }
 
 // Fill fills in the function pointers in the Features struct from the
@@ -328,6 +341,9 @@ func (ft *Features) Fill(f Fs) *Features {
 	if do, ok := f.(CleanUpper); ok {
 		ft.CleanUp = do.CleanUp
 	}
+	if do, ok := f.(ListRer); ok {
+		ft.ListR = do.ListR
+	}
 	return ft
 }
 
@@ -370,6 +386,9 @@ func (ft *Features) Mask(f Fs) *Features {
 	if mask.CleanUp == nil {
 		ft.CleanUp = nil
 	}
+	if mask.ListR == nil {
+		ft.ListR = nil
+	}
 	return ft
 }
 
@@ -479,6 +498,22 @@ type CleanUpper interface {
 	CleanUp() error
 }
 
+// ListRer is an optional interfaces for Fs
+type ListRer interface {
+	// ListR lists the objects and directories of the Fs starting
+	// from dir recursively into out.
+	//
+	// dir should be "" to start from the root, and should not
+	// have trailing slashes.
+	//
+	// This should return ErrDirNotFound (using out.SetError())
+	// if the directory isn't found.
+	//
+	// Don't implement this unless you have a more efficient way
+	// of listing recursively that doing a directory traversal.
+	ListR(out ListOpts, dir string)
+}
+
 // ObjectsChan is a channel of Objects
 type ObjectsChan chan Object
 

googlecloudstorage/googlecloudstorage.go

@@ -443,6 +443,12 @@ func (f *Fs) List(out fs.ListOpts, dir string) {
 	return
 }
 
+// ListR lists the objects and directories of the Fs starting
+// from dir recursively into out.
+func (f *Fs) ListR(out fs.ListOpts, dir string) {
+	f.List(out, dir) // FIXME
+}
+
 // Put the object into the bucket
 //
 // Copy the reader in to the new object which is returned
@@ -736,6 +742,7 @@ func (o *Object) MimeType() string {
 var (
 	_ fs.Fs        = &Fs{}
 	_ fs.Copier    = &Fs{}
+	_ fs.ListRer   = &Fs{}
 	_ fs.Object    = &Object{}
 	_ fs.MimeTyper = &Object{}
 )

s3/s3.go

@@ -626,6 +626,12 @@ func (f *Fs) List(out fs.ListOpts, dir string) {
 	return
 }
 
+// ListR lists the objects and directories of the Fs starting
+// from dir recursively into out.
+func (f *Fs) ListR(out fs.ListOpts, dir string) {
+	f.List(out, dir) // FIXME
+}
+
 // Put the Object into the bucket
 func (f *Fs) Put(in io.Reader, src fs.ObjectInfo, options ...fs.OpenOption) (fs.Object, error) {
 	// Temporary Object under construction
@@ -998,6 +1004,7 @@ func (o *Object) MimeType() string {
 var (
 	_ fs.Fs        = &Fs{}
 	_ fs.Copier    = &Fs{}
+	_ fs.ListRer   = &Fs{}
 	_ fs.Object    = &Object{}
 	_ fs.MimeTyper = &Object{}
 )

swift/swift.go

@@ -397,6 +397,12 @@ func (f *Fs) List(out fs.ListOpts, dir string) {
 	return
 }
 
+// ListR lists the objects and directories of the Fs starting
+// from dir recursively into out.
+func (f *Fs) ListR(out fs.ListOpts, dir string) {
+	f.List(out, dir) // FIXME
+}
+
 // Put the object into the container
 //
 // Copy the reader in to the new object which is returned
@@ -830,6 +836,7 @@ var (
 	_ fs.Fs        = &Fs{}
 	_ fs.Purger    = &Fs{}
 	_ fs.Copier    = &Fs{}
+	_ fs.ListRer   = &Fs{}
 	_ fs.Object    = &Object{}
 	_ fs.MimeTyper = &Object{}
 )

yandex/yandex.go

@@ -326,6 +326,12 @@ func (f *Fs) List(out fs.ListOpts, dir string) {
 	}
 }
 
+// ListR lists the objects and directories of the Fs starting
+// from dir recursively into out.
+func (f *Fs) ListR(out fs.ListOpts, dir string) {
+	f.List(out, dir) // FIXME
+}
+
 // NewObject finds the Object at remote.  If it can't be found it
 // returns the error fs.ErrorObjectNotFound.
 func (f *Fs) NewObject(remote string) (fs.Object, error) {
@@ -649,6 +655,7 @@ func (o *Object) MimeType() string {
 var (
 	_ fs.Fs      = (*Fs)(nil)
 	_ fs.Purger  = (*Fs)(nil)
+	_ fs.ListRer = (*Fs)(nil)
 	//_ fs.Copier = (*Fs)(nil)
 	_ fs.Object    = (*Object)(nil)
 	_ fs.MimeTyper = &Object{}