targets: Handle absence of apps for offline update

Apps might be explicitly turned off or intersection of target apps and
the app shortlist specified for offline update is empty (for specific
tag). In this case there is no a download URI to fetch an app tarball
for a given bundle. This change handles this case properly instead of
yielding an error.

Signed-off-by: Mike Sul <[email protected]>

subcommands/targets/offline-update.go

@@ -187,8 +187,13 @@ Notice that multiple targets in the same directory is only supported in LmP >= v
 				fmt.Printf("Downloading Apps fetched by the `assemble-system-image` run; build number: %d, tag: %s...\n", ti.version, ti.buildTag)
 				err = downloadApps(factory, targetName, ti.version, ti.buildTag, path.Join(dstDir, "apps"))
 			} else {
-				fmt.Printf("Downloading Apps fetched by the `publish-compose-apps` run; apps: %s, uri: %s...\n", ti.fetchedApps.Shortlist, ti.fetchedApps.Uri)
-				err = downloadAppsArchive(ti.fetchedApps.Uri, path.Join(dstDir, "apps"))
+				if len(ti.fetchedApps.Uri) > 0 {
+					fmt.Printf("Downloading Apps fetched by the `publish-compose-apps` run; apps: %s, uri: %s...\n", ti.fetchedApps.Shortlist, ti.fetchedApps.Uri)
+					err = downloadAppsArchive(ti.fetchedApps.Uri, path.Join(dstDir, "apps"))
+				} else {
+					fmt.Println("No apps found to fetch for an offline update to a given target. " +
+						"The bundle will update only rootfs/ostree. Check your factory configuration if this is not your intention.")
+				}
 			}
 			if herr := client.AsHttpError(err); herr != nil && herr.Response.StatusCode == 404 {
 				fmt.Println("WARNING: The Target Apps were not fetched by the `assemble` run, make sure that App preloading is enabled if needed. The update won't include any Apps!")