Add ListDirSorted function to list a directory

* fix error return of readFilesFn also

fs/operations.go

@@ -504,7 +504,72 @@ func readFilesFn(fs Fs, includeAll bool, dir string, add func(Object) error) (er
 			Debug(o, "Excluded from sync (and deletion)")
 		}
 	}
-	return nil
+	return list.Error()
+}
+
+// DirEntries is a slice of Object or *Dir
+type DirEntries []BasicInfo
+
+// Len is part of sort.Interface.
+func (ds DirEntries) Len() int {
+	return len(ds)
+}
+
+// Swap is part of sort.Interface.
+func (ds DirEntries) Swap(i, j int) {
+	ds[i], ds[j] = ds[j], ds[i]
+}
+
+// Less is part of sort.Interface.
+func (ds DirEntries) Less(i, j int) bool {
+	return ds[i].Remote() < ds[j].Remote()
+}
+
+// FIXME can use this in Mount
+
+// ListDirSorted reads Object and *Dir into entries for the given Fs.
+//
+// dir is the start directory, "" for root
+//
+// If includeAll is specified all files will be added, otherwise only
+// files passing the filter will be added.
+//
+// Files will be returned in sorted order
+func ListDirSorted(fs Fs, includeAll bool, dir string) (entries DirEntries, err error) {
+	list := NewLister().SetLevel(1)
+	if !includeAll {
+		list.SetFilter(Config.Filter)
+	}
+	list.Start(fs, dir)
+	for {
+		o, dir, err := list.Get()
+		if err != nil {
+			return nil, err
+		} else if o != nil {
+			// Make sure we don't delete excluded files if not required
+			if includeAll || Config.Filter.IncludeObject(o) {
+				entries = append(entries, o)
+			} else {
+				Debug(o, "Excluded from sync (and deletion)")
+			}
+		} else if dir != nil {
+			if includeAll || Config.Filter.IncludeDirectory(dir.Remote()) {
+				entries = append(entries, dir)
+			} else {
+				Debug(dir, "Excluded from sync (and deletion)")
+			}
+		} else {
+			// finishd since err, o, dir == nil
+			break
+		}
+	}
+	err = list.Error()
+	if err != nil {
+		return nil, err
+	}
+	// sort the directory entries by Remote
+	sort.Sort(entries)
+	return entries, nil
 }
 
 // Read a map of Object.Remote to Object for the given Fs.

fs/operations_test.go

@@ -883,3 +883,61 @@ func TestOverlapping(t *testing.T) {
 		assert.Equal(t, test.expected, actual, what)
 	}
 }
+
+func TestListDirSorted(t *testing.T) {
+	r := NewRun(t)
+	defer r.Finalise()
+
+	fs.Config.Filter.MaxSize = 10
+	defer func() {
+		fs.Config.Filter.MaxSize = -1
+	}()
+
+	r.WriteObject("a.txt", "hello world", t1)
+	r.WriteObject("zend.txt", "hello", t1)
+	r.WriteObject("sub dir/hello world", "hello world", t1)
+	r.WriteObject("sub dir/hello world2", "hello world", t1)
+	r.WriteObject("sub dir/sub sub dir/hello world3", "hello world", t1)
+	var items fs.DirEntries
+	var err error
+
+	// Turn the BasicInfo into a name, ending with a / if it is a
+	// dir
+	str := func(i int) string {
+		item := items[i]
+		name := item.Remote()
+		switch item.(type) {
+		case fs.Object:
+		case *fs.Dir:
+			name += "/"
+		default:
+			t.Fatalf("Unknown type %+v", item)
+		}
+		return name
+	}
+
+	items, err = fs.ListDirSorted(r.fremote, true, "")
+	require.NoError(t, err)
+	require.Len(t, items, 3)
+	assert.Equal(t, "a.txt", str(0))
+	assert.Equal(t, "sub dir/", str(1))
+	assert.Equal(t, "zend.txt", str(2))
+
+	items, err = fs.ListDirSorted(r.fremote, false, "")
+	require.NoError(t, err)
+	require.Len(t, items, 2)
+	assert.Equal(t, "sub dir/", str(0))
+	assert.Equal(t, "zend.txt", str(1))
+
+	items, err = fs.ListDirSorted(r.fremote, true, "sub dir")
+	require.NoError(t, err)
+	require.Len(t, items, 3)
+	assert.Equal(t, "sub dir/hello world", str(0))
+	assert.Equal(t, "sub dir/hello world2", str(1))
+	assert.Equal(t, "sub dir/sub sub dir/", str(2))
+
+	items, err = fs.ListDirSorted(r.fremote, false, "sub dir")
+	require.NoError(t, err)
+	require.Len(t, items, 1)
+	assert.Equal(t, "sub dir/sub sub dir/", str(0))
+}