fs: Implement UnWrapObject and UnWrapFs

fs/fs.go

@@ -1023,6 +1023,38 @@ type ObjectPair struct {
 	Src, Dst Object
 }
 
+// UnWrapFs unwraps f as much as possible and returns the base Fs
+func UnWrapFs(f Fs) Fs {
+	for {
+		unwrap := f.Features().UnWrap
+		if unwrap == nil {
+			break // not a wrapped Fs, use current
+		}
+		next := unwrap()
+		if next == nil {
+			break // no base Fs found, use current
+		}
+		f = next
+	}
+	return f
+}
+
+// UnWrapObject unwraps o as much as possible and returns the base object
+func UnWrapObject(o Object) Object {
+	for {
+		u, ok := o.(ObjectUnWrapper)
+		if !ok {
+			break // not a wrapped object, use current
+		}
+		next := u.UnWrap()
+		if next == nil {
+			break // no base object found, use current
+		}
+		o = next
+	}
+	return o
+}
+
 // Find looks for an RegInfo object for the name passed in.  The name
 // can be either the Name or the Prefix.
 //

fs/operations/lsjson.go

@@ -136,20 +136,8 @@ func ListJSON(ctx context.Context, fsrc fs.Fs, remote string, opt *ListJSONOpt,
 			if do, ok := entry.(fs.IDer); ok {
 				item.ID = do.ID()
 			}
-			if opt.ShowOrigIDs {
-				cur := entry
-				for {
-					u, ok := cur.(fs.ObjectUnWrapper)
-					if !ok {
-						break // not a wrapped object, use current id
-					}
-					next := u.UnWrap()
-					if next == nil {
-						break // no base object found, use current id
-					}
-					cur = next
-				}
-				if do, ok := cur.(fs.IDer); ok {
+			if o, ok := entry.(fs.Object); opt.ShowOrigIDs && ok {
+				if do, ok := fs.UnWrapObject(o).(fs.IDer); ok {
 					item.OrigID = do.ID()
 				}
 			}

fstest/fstests/fstests.go

@@ -330,14 +330,7 @@ func Run(t *testing.T, opt *Opt) {
 	// Return true if f (or any of the things it wraps) is bucket
 	// based but not at the root.
 	isBucketBasedButNotRoot := func(f fs.Fs) bool {
-		for {
-			doUnWrap := f.Features().UnWrap
-			if doUnWrap == nil {
-				break
-			}
-			f = doUnWrap()
-		}
-		return f.Features().BucketBased && strings.Contains(strings.Trim(f.Root(), "/"), "/")
+		return fs.UnWrapFs(f).Features().BucketBased && strings.Contains(strings.Trim(f.Root(), "/"), "/")
 	}
 
 	// Remove bad characters from Windows file name if set