fix channel transform

internal/chunk/chunk.go

@@ -31,8 +31,8 @@ type Chunk struct {
 	// header
 	Type      ChunkType `json:"t"`
 	Timestamp int64     `json:"ts"`
-	ChannelID string    `json:"id"`
-	Count     int       `json:"n"` // number of messages or files
+	ChannelID string    `json:"id,omitempty"`
+	Count     int       `json:"n,omitempty"` // number of messages or files
 
 	// the rest
 	IsThread bool `json:"r,omitempty"`

internal/chunk/directory.go

@@ -2,7 +2,6 @@ package chunk
 
 import (
 	"compress/gzip"
-	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
@@ -112,20 +111,16 @@ func readChanInfo(rs io.ReadSeeker) ([]slack.Channel, error) {
 // loadChannelsJSON loads channels json file and returns a slice of
 // slack.Channel.  It expects it to be GZIP compressed.
 func loadChannelsJSON(fullpath string) ([]slack.Channel, error) {
-	cf, err := openChunks(fullpath)
+	f, err := openChunks(fullpath)
 	if err != nil {
 		return nil, err
 	}
-	defer cf.Close()
-	return readChannelsJSON(cf)
-}
-
-func readChannelsJSON(r io.Reader) ([]slack.Channel, error) {
-	var ch []slack.Channel
-	if err := json.NewDecoder(r).Decode(&ch); err != nil {
+	defer f.Close()
+	cf, err := FromReader(f)
+	if err != nil {
 		return nil, err
 	}
-	return ch, nil
+	return cf.AllChannels()
 }
 
 // openChunks opens an existing chunk file and returns a ReadSeekCloser.  It

stream.go

@@ -527,6 +527,15 @@ func (cs *Stream) ListChannels(ctx context.Context, proc processor.Channels, p *
 		if err != nil {
 			return err
 		}
+
+		// this can happen if we're running the stream under the guest user.
+		// slack returns empty chunks.
+		if len(ch) == 0 {
+			if next == "" {
+				break
+			}
+			continue
+		}
 		if err := proc.Channels(ctx, ch); err != nil {
 			return err
 		}