handle empty RepoTags for ListImage

fix #155
Signed-off-by: yanxuean <[email protected]>

Signed-off-by: yanxuean <[email protected]>

Author: yanxuean

cmd/crictl/image.go

@@ -125,11 +125,7 @@ var listImageCommand = cli.Command{
 					printHeader = false
 					fmt.Fprintln(w, "IMAGE\tTAG\tIMAGE ID\tSIZE")
 				}
-				repoTags := "<none>"
-				if image.RepoTags != nil {
-					repoTags = image.RepoTags[0]
-				}
-				repoTagsPair := strings.Split(repoTags, ":")
+				repoTagsPair := normalizeRepoTagPair(image.RepoTags)
 				size := units.HumanSizeWithPrecision(float64(image.GetSize_()), 3)
 				trunctedImage := strings.TrimPrefix(image.Id, "sha256:")[:truncatedImageIDLen]
 				fmt.Fprintf(w, "%s\t%s\t%s\t%s\n", repoTagsPair[0], repoTagsPair[1], trunctedImage, size)
@@ -270,6 +266,21 @@ func getAuth(creds string) (*pb.AuthConfig, error) {
 	}, nil
 }
 
+// Support these cases as below:
+// "tag1:tag2", "tag1", "tag1:", ":tag2", ":", "", nil
+func normalizeRepoTagPair(repoTags []string) []string {
+	const defaultTag = "<none>"
+	if len(repoTags) == 0 {
+		return []string{defaultTag, defaultTag}
+	}
+	repoTagsPair := strings.Split(repoTags[0]+":"+defaultTag, ":")
+	// for ":tag2" case
+	if repoTagsPair[0] == "" {
+		repoTagsPair[0] = defaultTag
+	}
+	return repoTagsPair[0:2]
+}
+
 // PullImage sends a PullImageRequest to the server, and parses
 // the returned PullImageResponse.
 func PullImage(client pb.ImageServiceClient, image string, auth *pb.AuthConfig) (*pb.PullImageResponse, error) {